Page 1
User’s Manual
Model 331
Temperature Controller
Includes Coverage For:
Model 331S and Model 331E
Lake Shore Cryotronics, Inc.
575 McCorkle Blvd.
Westerville, Ohio 43082-8888 USA
E-mail addresses:
Visit our website at:
www.lakeshore.com
Fax: (614) 891-1392
Telephone: (614) 891-2243
Methods and apparatus disclosed and described herein have been developed solely on company funds of Lake Shore Cryotronics, Inc.
No government or other contractual support or relationship whatsoever has existed which in any way affects or mitigates proprietary
rights of Lake Shore Cryotronics, Inc. in these developments. Methods and apparatus disclosed herein may be subject to U.S. Patents
existing or applied for. Lake Shore Cryotronics, Inc. reserves the right to add, improve, modify, or withdraw functions, design
modifications, or products at any time without notice. Lake Shore shall not be liable for errors contained herein or for incidental or
consequential damages in connection with furnishing, performance, or use of this material.
Revision: 1.9 P/N 119-031 14 May 2009
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Lake Shore Model 331 Temperature Controller User’s Manual
1. Lake Shore warrants that this Lake Shore product (the
“Product”) will be free from defects in materials and
workmanship for the Warranty Period specified above (the
“Warranty Period”). If Lake Shore receives notice of any such
defects during the Warranty Period and the Product is shipped
freight prepaid, Lake Shore will, at its option, either repair or
replace the Product if it is so defective without charge to the
owner for parts, service labor or associated customary return
shipping cost. Any such replacement for the Product may be
either new or equivalent in performance to new. Replacement or
repaired parts will be warranted for only the unexpired portion of
the original warranty or 90 days (whichever is greater).
2. Lake Shore warrants the Product only if it has been sold by an
authorized Lake Shore employee, sales representative, dealer
or original equipment manufacturer (OEM).
3. The Product may contain remanufactured parts equivalent to
new in performance or may have been subject to incidental use.
4. The Warranty Period begins on the date of delivery of the
Product or later on the date of installation of the Product if the
Product is installed by Lake Shore, provided that if you schedule
or delay the Lake Shore installation for more than 30 days after
delivery the Warranty Period begins on the 31st day after
delivery.
5. This limited warranty does not apply to defects in the Product
resulting from (a) improper or inadequate maintenance, repair or
calibration, (b) fuses, software and non-rechargeable batteries,
(c) software, interfacing, parts or other supplies not furnished by
Lake Shore, (d) unauthorized modification or misuse, (e)
operation outside of the published specifications or (f) improper
site preparation or maintenance.
6. TO THE EXTENT ALLOWED BY APPLICABLE LAW, THE
ABOVE WARRANTIES ARE EXCLUSIVE AND NO OTHER
WARRANTY OR CONDITION, WHETHER WRITTEN OR
ORAL, IS EXPRESSED OR IMPLIED. LAKE SHORE
SPECIFICALLY DISCLAIMS ANY IMPLIED WARRANTIES OR
CONDITIONS OF MERCHANTABILITY, SATISFACTORY
QUALITY AND/OR FITNESS FOR A PARTICULAR PURPOSE
WITH RESPECT TO THE PRODUCT. Some countries, states
or provinces do not allow limitations on an implied warranty, so
the above limitation or exclusion might not apply to you. This
warranty gives you specific legal rights and you might also have
other rights that vary from country to country, state to state or
province to province.
7. TO THE EXTENT ALLOWED BY APPLICABLE LAW, THE
REMEDIES IN THIS WARRANTY STATEMENT ARE YOUR
SOLE AND EXCLUSIVE REMEDIES.
8. EXCEPT TO THE EXTENT PROHIBITED BY APPLICABLE
LAW, IN NO EVENT WILL LAKE SHORE OR ANY OF ITS
SUBSIDIARIES, AFFILIATES OR SUPPLIERS BE LIABLE FOR
DIRECT, SPECIAL, INCIDENTAL, CONSEQUENTIAL OR
OTHER DAMAGES (INCLUDING LOST PROFIT, LOST DATA
OR DOWNTIME COSTS) ARISING OUT OF THE USE,
INABILITY TO USE OR RESULT OF USE OF THE PRODUCT,
WHETHER BASED IN WARRANTY, CONTRACT, TORT OR
OTHER LEGAL THEORY, AND WHETHER OR NOT LAKE
SHORE HAS BEEN ADVISED OF THE POSSIBILITY OF
SUCH DAMAGES. Your use of the Product is entirely at your
own risk. Some countries, states and provinces do not allow the
exclusion of liability for incidental or consequential damages, so
the above limitation may not apply to you.
LIMITED WARRANTY STATEMENT
WARRANTY PERIOD: ONE (1) YEAR
LIMITED WARRANTY STATEMENT (Continued)
9. EXCEPT TO THE EXTENT ALLOWED BY APPLICABLE LAW,
THE TERMS OF THIS LIMITED WARRANTY STATEMENT DO
NOT EXCLUDE, RESTRICT OR MODIFY, AND ARE IN
ADDITION TO, THE MANDATORY STATUTORY RIGHTS
APPLICABLE TO THE SALE OF THE PRODUCT TO YOU.
CERTIFICATION
Lake Shore certifies that this product has been inspected and
tested in accordance with its published specifications and that this
product met its published specifications at the time of shipment.
The accuracy and calibration of this product at the time of
shipment are traceable to the United States National Institute of
Standards and Technology (NIST); formerly known as the National
Bureau of Standards (NBS).
FIRMWARE LIMITATIONS
Lake Shore has worked to ensure that the Model 331 firmware is
as free of errors as possible, and that the results you obtain from
the instrument are accurate and reliable. However, as with any
computer-based software, the possibility of errors exists.
In any important research, as when using any laboratory
equipment, results should be carefully examined and rechecked
before final conclusions are drawn. Neither Lake Shore nor anyone
else involved in the creation or production of this firmware can pay
for loss of time, inconvenience, loss of use of the product, or
property damage caused by this product or its failure to work, or
any other incidental or consequential damages. Use of our product
implies that you understand the Lake Shore license agreement and
statement of limited warranty.
FIRMWARE LICENSE AGREEMENT
The firmware in this instrument is protected by United States
copyright law and international treaty provisions. To maintain the
warranty, the code contained in the firmware must not be modified.
Any changes made to the code is at the user’s risk. Lake Shore will
assume no responsibility for damage or errors incurred as result of
any changes made to the firmware.
Under the terms of this agreement you may only use the Model
331 firmware as physically installed in the instrument. Archival
copies are strictly forbidden. You may not decompile, disassemble,
or reverse engineer the firmware. If you suspect there are
problems with the firmware, return the instrument to Lake Shore for
repair under the terms of the Limited Warranty specified above.
Any unauthorized duplication or use of the Model 331 firmware in
whole or in part, in print, or in any other storage and retrieval
system is forbidden.
TRADEMARK ACKNOWLEDGMENT
Many manufacturers and sellers claim designations used to
distinguish their products as trademarks. Where those
designations appear in this manual and Lake Shore was aware of
a trademark claim, they appear with initial capital letters and the ™
®
or
symbol.
CalCurve™, Cernox™, Duo-Twist™, Quad-Lead™,
Quad-Twist™, Rox™, and SoftCal™ are trademarks
of Lake Shore Cryotronics, Inc.
MS-DOS
®
and Windows/95/98/NT/2000® are trademarks of
Microsoft Corp.
NI-488.2™ is a trademark of National Instruments.
PC, XT, AT, and PS-2 are trademarks of IBM.
Copyright © 2000 – 2002 & 2004 – 2009 by Lake Shore Cryotronics, Inc. All rights reserved. No portion of this manual
may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical,
photocopying, recording, or otherwise, without the express written permission of Lake Shore.
A
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Lake Shore Model 331 Temperature Controller User’s Manual
DECLARATION OF CONFORMITY
We: Lake Shore Cryotronics, Inc.
575 McCorkle Blvd.
Westerville OH 43082-8888 USA
hereby declare that the equipment specified conforms to the following
Directives and Standards:
Application of Council Directives: .............................. 73/23/EEC
89/336/EEC
Standards to which Conformity is declared: .............. EN61010-1:2001
Overvoltage II
Pollution Degree 2
EN61326 A2:2001
Class A
Annex B
Model Number: .......................................................... 331
Ed Maloof
Printed Name
Vice President of Engineering
Position
B
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Lake Shore Model 331 Temperature Controller User’s Manual
Electromagnetic Compatibility (EMC) for the Model 331 Temperature Controller
Electromagnetic Compatibility (EMC) of electronic equipment is a growing concern worldwide.
Emissions of and immunity to electromagnetic interference is now part of the design and manufacture
of most electronics. To qualify for the CE Mark, the Model 331 meets or exceeds the requirements of
the European EMC Directive 89/336/EEC as a CLASS A product. A Class A product is allowed to
radiate more RF than a Class B product and must include the following warning:
WARNING: This is a Class A product. In a domestic environment, this product may
cause radio interference in which case the user may be required to take
The instrument was tested under normal operating conditions with sensor and interface cables
attached. If the installation and operating instructions in the User’s Manual are followed, there should
be no degradation in EMC performance.
This instrument is not intended for use in close proximity to RF Transmitters such as two-way radios
and cell phones. Exposure to RF interference greater than that found in a typical laboratory
environment may disturb the sensitive measurement circuitry of the instrument.
Pay special attention to instrument cabling. Improperly installed cabling may defeat even the best
EMC protection. For the best performance from any precision instrument, follow the grounding and
shielding instructions in the User’s Manual. In addition, the installer of the Model 331 should consider
the following:
• Shield measurement and computer interface cables.
• Leave no unused or unterminated cables attached to the instrument.
• Make cable runs as short and direct as possible. Higher radiated emissions is possible with
long cables.
• Do not tightly bundle cables that carry different types of signals.
adequate measures.
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Lake Shore Model 331 Temperature Controller User’s Manual
TABLE OF CONTENTS
Chapter/Paragraph Title Page
1 INTRODUCTION .................................................................................................................................................... 1-1
1.0 PRODUCT DESCRIPTION ............................................................................................................... 1-1
1.1 SENSOR SELECTION ...................................................................................................................... 1-4
1.2 SPECIFICATIONS ............................................................................................................................. 1-6
1.3 SAFETY SUMMARY ......................................................................................................................... 1-9
1.4 SAFETY SYMBOLS ........................................................................................................................ 1-10
2 COOLING SYSTEM DESIGN ................................................................................................................................. 2-1
2.0 GENERAL ......................................................................................................................................... 2-1
2.1 TEMPERATURE SENSOR SELECTION .......................................................................................... 2-1
2.1.1 Temperature Range ....................................................................................................................... 2-1
2.1.2 Sensor Sensitivity .......................................................................................................................... 2-1
2.1.3 Environmental Conditions .............................................................................................................. 2-2
2.1.4 Measurement Accuracy ................................................................................................................. 2-2
2.1.5 Sensor Package ............................................................................................................................. 2-2
2.2 CALIBRATED SENSORS ................................................................................................................. 2-2
2.2.1 Traditional Calibration .................................................................................................................... 2-2
2.2.2 SoftCal™........................................................................................................................................ 2-3
2.2.3 Standard Curves ............................................................................................................................ 2-3
2.2.4 CalCurve™ .................................................................................................................................... 2-3
2.3 SENSOR INSTALLATION ................................................................................................................. 2-5
2.3.1 Mounting Materials ......................................................................................................................... 2-5
2.3.2 Sensor Location ............................................................................................................................. 2-5
2.3.3 Thermal Conductivity ..................................................................................................................... 2-5
2.3.4 Contact Area .................................................................................................................................. 2-5
2.3.5 Contact Pressure ........................................................................................................................... 2-6
2.3.6 Lead Wire....................................................................................................................................... 2-6
2.3.7 Lead Soldering ............................................................................................................................... 2-7
2.3.8 Heat Sinking Leads ........................................................................................................................ 2-7
2.3.9 Thermal Radiation .......................................................................................................................... 2-7
2.4 HEATER SELECTION AND INSTALLATION .................................................................................... 2-7
2.4.1 Heater Resistance and Power ....................................................................................................... 2-7
2.4.2 Heater Location .............................................................................................................................. 2-8
2.4.3 Heater Types ................................................................................................................................. 2-8
2.4.4 Heater Wiring ................................................................................................................................. 2-8
2.5 CONSIDERATIONS FOR GOOD CONTROL ................................................................................... 2-8
2.5.1 Thermal Conductivity ..................................................................................................................... 2-8
2.5.2 Thermal Lag ................................................................................................................................... 2-8
2.5.3 Two-Sensor Approach ................................................................................................................... 2-9
2.5.4 Thermal Mass ................................................................................................................................ 2-9
2.5.5 System Nonlinearit y ....................................................................................................................... 2-9
2.6 PID CONTROL .................................................................................................................................. 2-9
2.6.1 Proportional (P) ............................................................................................................................ 2-10
2.6.2 Integral (I)..................................................................................................................................... 2-10
2.6.3 Derivative (D) ............................................................................................................................... 2-10
2.6.4 Manual Heater Power (MHP) Output ........................................................................................... 2-10
2.7 MANUAL TUNING ........................................................................................................................... 2-12
2.7.1 Setting Heater Range .................................................................................................................. 2-12
2.7.2 Tuning Proportional ...................................................................................................................... 2-12
2.7.3 Tuning Integral ............................................................................................................................. 2-13
2.7.4 Tuning Derivative ......................................................................................................................... 2-13
2.8 AUTOTUNING ................................................................................................................................. 2-13
2.9 ZONE TUNING ................................................................................................................................ 2-14
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Lake Shore Model 331 Temperature Controller User’s Manual
TABLE OF CONTENTS (Continued)
Chapter/Paragraph Title Page
3 INSTALLATION ...................................................................................................................................................... 3-1
3.0 GENERAL ......................................................................................................................................... 3-1
3.1 INSPECTION AND UNPACKING ...................................................................................................... 3-1
3.2 REPACKAGING FOR SHIPMENT .................................................................................................... 3-1
3.3 REAR PANEL DEFINITION ............................................................................................................... 3-2
3.4 LINE INPUT ASSEMBLY ................................................................................................................... 3-3
3.4.1 Line Voltage ................................................................................................................................... 3-3
3.4.2 Line Fuse and Fuse Holder ............................................................................................................ 3-3
3.4.3 Power Cord .................................................................................................................................... 3-3
3.4.4 Power Switch ................................................................................................................................. 3-4
3.5 DIODE/RESISTOR SENSOR INPUTS .............................................................................................. 3-4
3.5.1 Sensor Input Connector and Pinout ............................................................................................... 3-4
3.5.2 Sensor Lead Cable ........................................................................................................................ 3-5
3.5.3 Grounding and Shielding Sensor Leads ......................................................................................... 3-5
3.5.4 Sensor Polarity ............................................................................................................................... 3-5
3.5.5 Four-Lead Sensor Measurement ................................................................................................... 3-6
3.5.6 Two-Lead Sensor Measurement .................................................................................................... 3-6
3.5.7 Lowering Measurement Noise........................................................................................................ 3-6
3.6 THERMOCOUPLE SENSOR INPUTS .............................................................................................. 3-7
3.6.1 Sensor Input Terminals .................................................................................................................. 3-7
3.6.2 Thermocouple Installation .............................................................................................................. 3-7
3.6.3 Grounding and Shielding ................................................................................................................ 3-7
3.7 HEATER OUTPUT SETUP ............................................................................................................... 3-8
3.7.1 Loop 1 Output ................................................................................................................................ 3-8
3.7.2 Loop 1 Heater Output Connector ................................................................................................... 3-8
3.7.3 Loop 1 Heater Output Wiring ......................................................................................................... 3-8
3.7.4 Loop 1 Heater Output Noise .......................................................................................................... 3-9
3.7.5 Loop 2 Output ................................................................................................................................ 3-9
3.7.6 Loop 2 Output Resistance .............................................................................................................. 3-9
3.7.7 Loop 2 Output Connector ............................................................................................................... 3-9
3.7.8 Loop 2 Heater Protection ............................................................................................................... 3-9
3.7.9 Boosting the Output Power ............................................................................................................ 3-9
3.8 ANALOG OUTPUT .......................................................................................................................... 3-10
3.9 RELAYS .......................................................................................................................................... 3-10
3.10 INITIAL SETUP AND SYSTEM CHECKOUT PROCEDURE .......................................................... 3-11
4 OPERATION ........................................................................................................................................................... 4-1
4.0 GENERAL ......................................................................................................................................... 4-1
4.1 FRONT PANEL DESCRIPTION ........................................................................................................ 4-1
4.1.1 Keypad Definitions ......................................................................................................................... 4-1
4.1.2 Annunciators .................................................................................................................................. 4-3
4.1.3 General Keypad Operation ............................................................................................................ 4-3
4.1.4 Display Definition ........................................................................................................................... 4-4
4.2 TURNING POWER ON ..................................................................................................................... 4-4
4.3 DISPLAY FORMAT AND SOURCE (UNITS) SELECTION ............................................................... 4-5
4.4 INPUT SETUP ................................................................................................................................... 4-7
4.4.1 Diode Sensor Input Setup - 10 µA Excitation Current .................................................................... 4-7
4.4.2 Diode Sensor Input Setup - 1 mA Excitation Current ..................................................................... 4-8
4.4.3 Resistor Sensor Input Setup .......................................................................................................... 4-9
4.4.3.1 Thermal EMF Compensation ...................................................................................................... 4-9
4.4.4 Thermocouple Sensor Input Setup ............................................................................................... 4-10
4.4.4.1 Room-Temperature Compensation .......................................................................................... 4-10
4.4.4.2 Room-Temperature Calibration Procedure ............................................................................... 4-11
4.5 CURVE SELECTION ....................................................................................................................... 4-12
4.5.1 Diode Sensor Curve Selection ..................................................................................................... 4-13
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Lake Shore Model 331 Temperature Controller User’s Manual
TABLE OF CONTENTS (Continued)
Chapter/Paragraph Title Page
4.5.2 Resistor Sensor Curve Selection ................................................................................................. 4-13
4.5.3 Thermocouple Sensor Curve Selection ....................................................................................... 4-13
4.6 TEMPERATURE CONTROL ........................................................................................................... 4-14
4.6.1 Control Loops ............................................................................................................................... 4-14
4.6.2 Control Modes .............................................................................................................................. 4-15
4.6.3 Tuning Modes .............................................................................................................................. 4-15
4.7 CONTROL SETUP .......................................................................................................................... 4-15
4.8 MANUAL TUNING ........................................................................................................................... 4-17
4.8.1 Manually Setting Proportional (P) ................................................................................................ 4-17
4.8.2 Manually Setting Integral (I) ......................................................................................................... 4-17
4.8.3 Manually Setting Derivative (D) .................................................................................................... 4-18
4.8.4 Setting Manual Heater Power (MHP) Output ............................................................................... 4-18
4.9 AUTOTUNE (CLOSED-LOOP PID CONTROL) .............................................................................. 4-19
4.10 ZONE SETTINGS (CLOSED-LOOP CONTROL) ............................................................................ 4-20
4.11 SETPOINT....................................................................................................................................... 4-23
4.12 RAMP .............................................................................................................................................. 4-24
4.13 HEATER RANGE AND HEATER OFF ............................................................................................ 4-25
4.14 MATH .............................................................................................................................................. 4-26
4.14.1 Max/Min ....................................................................................................................................... 4-26
4.14.2 Linear ........................................................................................................................................... 4-27
4.14.3 Filter ............................................................................................................................................. 4-28
4.15 ALARMS AND RELAYS .................................................................................................................. 4-29
4.15.1 Alarms .......................................................................................................................................... 4-29
4.15.2 Relays .......................................................................................................................................... 4-31
4.16 ANALOG OUTPUT .......................................................................................................................... 4-32
4.16.1 Analog Output In Input Mode ....................................................................................................... 4-32
4.16.2 Analog Output In Manual Mode ................................................................................................... 4-34
4.16.3 Analog Output In Loop 2 Mode .................................................................................................... 4-35
4.17 LOCKING AND UNLOCKING THE KEYPAD .................................................................................. 4-35
4.18 DISPLAY BRIGHTNESS ................................................................................................................. 4-36
4.19 REMOTE/LOCAL ............................................................................................................................ 4-36
4.20 INTERFACE .................................................................................................................................... 4-36
4.21 DEFAULT VALUES ......................................................................................................................... 4-37
5 ADVANCED OPERATION ..................................................................................................................................... 5-1
5.0 GENERAL ......................................................................................................................................... 5-1
5.1 CURVE NUMBERS AND STORAGE ................................................................................................ 5-1
5.1.1 Curve Header Parameters ............................................................................................................. 5-1
5.1.2 Curve Breakpoints ......................................................................................................................... 5-2
5.2 FRONT PANEL CURVE ENTRY OPERATIONS .............................................................................. 5-2
5.2.1 Edit Curve ...................................................................................................................................... 5-4
5.2.1.1 Thermocouple Curve Considerations ......................................................................................... 5-5
5.2.2 Erase Curve ................................................................................................................................... 5-6
5.2.3 Copy Curve .................................................................................................................................... 5-6
5.3 SOFTCAL™ ...................................................................................................................................... 5-7
5.3.1 SoftCal With Silicon Diode Sensors ............................................................................................... 5-7
5.3.2 SoftCal Accuracy With Silicon Diode Sensors ............................................................................... 5-8
5.3.3 SoftCal With Platinum Sensors ...................................................................................................... 5-9
5.3.4 SoftCal Accuracy With Platinum Sensors ...................................................................................... 5-9
5.3.5 SoftCal Calibration Curve Creation .............................................................................................. 5-10
6 COMPUTER INTERFACE OPERATION ................................................................................................................ 6-1
6.0 GENERAL ......................................................................................................................................... 6-1
6.1 IEEE-488 INTERFACE ...................................................................................................................... 6-1
6.1.1 IEEE-488 Interface Parameters ..................................................................................................... 6-2
6.1.2 IEEE-488 Command Structure ....................................................................................................... 6-2
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Lake Shore Model 331 Temperature Controller User’s Manual
TABLE OF CONTENTS (Continued)
Chapter/Paragraph Title Page
6.1.2.1 Bus Control Commands ............................................................................................................. 6-2
6.1.2.2 Common Commands .................................................................................................................. 6-3
6.1.2.3 Device Specific Commands ........................................................................................................ 6-3
6.1.2.4 Message Strings ......................................................................................................................... 6-3
6.1.3 Status Registers ............................................................................................................................. 6-4
6.1.3.1 Status Byte Register and Service Request Enable Register ...................................................... 6-4
6.1.3.2 Standard Event Status Register and Standard Event Status Enable Register ........................... 6-4
6.1.4 IEEE Interface Example Programs ................................................................................................. 6-5
6.1.4.1 IEEE-488 Interface Board Installation for Visual Basic Program ................................................ 6-5
6.1.4.2 Visual Basic IEEE-488 Interface Program Setup ........................................................................ 6-7
6.1.4.3 IEEE-488 Interface Board Installation for Quick Basic Program ............................................... 6-10
6.1.4.4 Quick Basic Program ................................................................................................................ 6-10
6.1.4.5 Program Operation ................................................................................................................... 6-13
6.1.5 Troubleshooting ........................................................................................................................... 6-13
6.2 SERIAL INTERFACE OVERVIEW .................................................................................................. 6-14
6.2.1 Physical Connection ..................................................................................................................... 6-14
6.2.2 Hardware Support ........................................................................................................................ 6-14
6.2.3 Character Format ......................................................................................................................... 6-15
6.2.4 Message Strings .......................................................................................................................... 6-15
6.2.5 Message Flow Control ................................................................................................................. 6-16
6.2.6 Changing Baud Rate .................................................................................................................... 6-16
6.2.7 Serial Interface Example Programs .............................................................................................. 6-17
6.2.7.1 Visual Basic Serial Interface Program Setup ............................................................................ 6-17
6.2.7.2 Quick Basic Serial Interface Program Setup ............................................................................ 6-20
6.2.7.3 Program Operation ................................................................................................................... 6-21
6.2.8 Troubleshooting ........................................................................................................................... 6-21
6.3 COMMAND SUMMARY .................................................................................................................. 6-22
6.3.1 Interface Commands (Alphabetical Listing) .................................................................................. 6-24
7 OPTIONS AND ACCESSORIES ............................................................................................................................ 7-1
7.0 GENERAL ......................................................................................................................................... 7-1
7.1 MODELS ........................................................................................................................................... 7-1
7.2 OPTIONS .......................................................................................................................................... 7-1
7.3 ACCESSORIES ................................................................................................................................. 7-2
7.4 MODEL 3003 HEATER OUTPUT CONDITIONER ............................................................................ 7-4
8 SERVICE ................................................................................................................................................................ 8-1
8.0 GENERAL ......................................................................................................................................... 8-1
8.1 ELECTROSTATIC DISCHARGE ....................................................................................................... 8-1
8.1.1 Identification of Electrostatic Discharge Sensitive Components ..................................................... 8-1
8.1.2 Handling Electrostatic Discharge Sensitive Components ............................................................... 8-1
8.2 LINE VOLTAGE SELECTION ........................................................................................................... 8-2
8.3 FUSE REPLACEMENT ..................................................................................................................... 8-2
8.4 REAR PANEL CONNECTOR DEFINITIONS .................................................................................... 8-3
8.4.1 Serial Interface Cable Wiring ......................................................................................................... 8-5
8.4.2 IEEE-488 Interface Connector ....................................................................................................... 8-6
8.5 TOP OF ENCLOSURE REMOVE AND REPLACE PROCEDURE .................................................... 8-7
8.6 FIRMWARE AND NOVRAM REPLACEMENT .................................................................................. 8-7
8.7 JUMPERS ......................................................................................................................................... 8-8
8.8 ERROR MESSAGES ......................................................................................................................... 8-8
8.9 CALIBRATION PROCEDURE ......................................................................................................... 8-10
8.9.1 Equipment Required for Calibration ............................................................................................. 8-10
8.9.2 Diode/Resistor Sensor Input Calibration ...................................................................................... 8-11
8.9.2.1 Sensor Input Calibration Setup and Serial Communication Verification ................................... 8-11
8.9.2.2 10 µA Current Source Calibration and 1 mA Current Source Verification ................................. 8-11
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Lake Shore Model 331 Temperature Controller User’s Manual
Chapter/Paragraph Title Page
8.9.2.3 Diode Input Ranges Calibration ................................................................................................ 8-12
8.9.2.4 Resistive Input Ranges Calibration .......................................................................................... 8-13
8.9.3 Diode Sensor Input Calibration - 1 mA Excitation Current ........................................................... 8-14
8.9.4 Thermocouple Sensor Input Calibration ....................................................................................... 8-14
8.9.4.1 Sensor Input Calibration Setup ................................................................................................. 8-14
8.9.4.2 Thermocouple Input Ranges Calibration .................................................................................. 8-14
8.9.5 Analog Output Calibration (Model 331S Only) ............................................................................. 8-15
8.9.5.1 Analog Output Calibration ........................................................................................................ 8-16
8.9.6 Calibration Specific Interface Commands .................................................................................... 8-17
APPENDIX A – GLOSSARY OF TERMINOLOGY ........................................................................................................ A-1
APPENDIX B – TEMPERATURE SCALES .................................................................................................................. B-1
APPENDIX C – HANDLING OF LIQUID HELIUM AND NITROGEN ............................................................................ C-1
APPENDIX D – CURVE TABLES ................................................................................................................................. D-1
LIST OF ILLUSTRATIONS
Figure No. Title Page
1-1 Model 331S Rear Panel Connections .......................................................................................................... 1-3
2-1 Silicon Diode Sensor Calibrations and CalCurve ......................................................................................... 2-4
2-2 Typical Sensor Installation In A Mechanical Refrigerator ............................................................................. 2-6
2-3 Examples of PID Control ............................................................................................................................ 2-11
3-1 Model 331 Rear Panel .................................................................................................................................. 3-2
3-2 Line Input Assembly ..................................................................................................................................... 3-3
3-3 Diode/Resistor Input Connector ................................................................................................................... 3-4
3-4 Thermocouple Input Definition and Common Connector Polarities .............................................................. 3-7
3-5 RELAYS and ANALOG OUTPUT Terminal Block ...................................................................................... 3-10
4-1 Model 331 Front Panel ................................................................................................................................. 4-1
4-2 Display Definition ......................................................................................................................................... 4-4
4-3 Display Format Definition ............................................................................................................................. 4-5
4-4 Record of Zone Settings ............................................................................................................................. 4-22
4-5 Deadband Example .................................................................................................................................... 4-29
4-6 Relay Settings ............................................................................................................................................ 4-31
5-1 SoftCal Temperature Ranges for Silicon Diode Sensors .............................................................................. 5-8
5-2 SoftCal Temperature Ranges for Platinum Sensors..................................................................................... 5-9
6-1 GPIB Setting Configuration .......................................................................................................................... 6-6
6-2 DEV 12 Device Template Configuration ....................................................................................................... 6-6
6-3 Typical National Instruments GPIB Configuration from IBCONF.EXE........................................................ 6-11
7-1 Model 331 Sensor and Heater Cable Assembly ........................................................................................... 7-4
7-2 Model 3003 Heater Output Conditioner ........................................................................................................ 7-4
7-3 Model RM-1/2 Rack-Mount Kit ..................................................................................................................... 7-5
7-4 Model RM-2 Dual Rack-Mount Kit ................................................................................................................ 7-6
8-1 Power Fuse Access ...................................................................................................................................... 8-2
8-2 Sensor INPUT A and B Connector Details ................................................................................................... 8-3
8-3 HEATER OUTPUT Connector Details .......................................................................................................... 8-3
8-4 RELAYS and ANALOG OUTPUT Terminal Block ........................................................................................ 8-4
8-5 RS-232 Connector Details ............................................................................................................................ 8-4
8-6 IEEE-488 Rear Panel Connector Details ...................................................................................................... 8-6
8-7 Location of Internal Components ................................................................................................................. 8-9
B-1 Temperature Scale Comparison .................................................................................................................. B-1
C-1 Typical Cryogenic Storage Dewar ................................................................................................................ C-1
TABLE OF CONTENTS (Continued)
Table of Contents v
Page 10
Lake Shore Model 331 Temperature Controller User’s Manual
LIST OF TABLES
Table No. Title Page
1-1 Sensor Temperature Range ......................................................................................................................... 1-4
1-2 Typical Sensor Performance ........................................................................................................................ 1-5
1-3 Input Specifications ...................................................................................................................................... 1-6
1-4 Sensor Input Configuration ........................................................................................................................... 1-6
1-5 Heater Output ............................................................................................................................................... 1-7
1-6 Loop 1 Full Scale Heater Power at Typical Resistance ................................................................................ 1-7
4-1 Sensor Input Types ...................................................................................................................................... 4-7
4-2 Sensor Curves ............................................................................................................................................ 4-12
4-3 Comparison of Control Loops 1 and 2 ........................................................................................................ 4-14
4-4 Linear Equation Configuration .................................................................................................................... 4-27
4-5 Default Values ............................................................................................................................................ 4-38
5-1 Curve Header Parameters ............................................................................................................................ 5-3
5-2 Recommended Curve Parameters ............................................................................................................... 5-3
6-1 IEEE-488 Interface Program Control Properties ........................................................................................... 6-8
6-2 Visual Basic IEEE-488 Interface Program .................................................................................................... 6-9
6-3 Quick Basic IEEE-488 Interface Program ................................................................................................... 6-12
6-4 Serial Interface Specifications .................................................................................................................... 6-15
6-5 Serial Interface Program Control Properties ............................................................................................... 6-18
6-6 Visual Basic Serial Interface Program ........................................................................................................ 6-19
6-7 Quick Basic Serial Interface Program ......................................................................................................... 6-20
6-8 Command Summary .................................................................................................................................. 6-23
8-1 Calibration Table for Diode Ranges ........................................................................................................... 8-12
8-2 Calibration Table for Resistive Ranges ...................................................................................................... 8-14
8-3 Calibration Table for Thermocouple Ranges .............................................................................................. 8-15
B-1 Temperature Conversion Table .................................................................................................................... B-2
C-1 Comparison of Liquid Helium and Liquid Nitrogen ...................................................................................... C-1
D-1 DT-470 Silicon Diode Curve ........................................................................................................................ D-1
D-2 DT-670 Silicon Diode Curve ................................................................................................
D-3 DT-500 Series Silicon Diode Curves ........................................................................................................... D-2
D-4 PT-100/-1000 Platinum RTD Curves ........................................................................................................... D-3
D-5 RX-102A Rox™ Curve ................................................................................................................................ D-4
D-6 RX-202A Rox™ Curve ................................................................................................................................ D-5
D-7 Type K Thermocouple Curve ....................................................................................................................... D-6
D-8 Type E Thermocouple Curve ....................................................................................................................... D-7
D-9 Type T Thermocouple Curve ....................................................................................................................... D-8
D-10 Chromel-AuFe 0.03% Thermocouple Curve ................................................................................................ D-9
D-11 Chromel-AuFe 0.07% Thermocouple Curve .............................................................................................. D-10
........................ D-2
vi Table of Contents
Page 11
Lake Shore Model 331 Temperature Controller User’s Manual
CHAPTER 1
INTRODUCTION
1.0 PRODUCT DESCRIPTION
The Model 331 Temperature Controller combines the easy operation and unsurpassed reliability of the
Model 330 with improved sensor input and interface flexibility, including compatibility with negative
temperature coefficient (NTC) resistance temperature detectors (RTDs). Backed by the Lake Shore
tradition of excellence in cryogenic sensors and instrumentation, the Model 331 Temperature Controller
sets the standard for mid-price range temperature control instruments.
The Model 331 Temperature Controller is available in two versions. The Model 331S is fully equipped
for interface and control flexibility. The Model 331E shares measurement and display capability with the
Model 331S, but does not include the IEEE-488 interface, relays, analog voltage output, or a second
control loop.
Sensor Inputs
The Model 331 Temperature Controller is designed for high performance over a wide operating
temperature range and in difficult sensing conditions. The Model 331 features two inputs, with a highresolution 24-bit analog-to-digital converter and separate current source for each input. Sensors are
optically isolated from other instrument functions for quiet and repeatable sensor measurements.
Sensor data from each input can be read up to ten times per second, with display updates twice each
second. The Model 331 uses current reversal to eliminate thermal EMF errors in resistance sensors.
Standard temperature response curves for silicon diodes, platinum RTDs, and many thermocouples are
included. Up to twenty 200-point CalCurves™ for Lake Shore calibrated sensors or user curves can be
loaded into non-volatile memory via a computer interface or the instrument front panel. A built-in
SoftCal™
storage as user curves.
1
algorithm can also be used to generate curves for silicon diodes and platinum RTDs, for
1
The Lake Shore SoftCal™ algorithm for silicon diode and platinum RTD sensors is a good solution for applications
requiring more accuracy than a standard sensor curve but not in need of traditional calibration. SoftCal uses the
predictability of a standard curve to improve the accuracy of an individual sensor around a few known temperature
reference points. Both versions of the Model 331 can generate SoftCal curves.
Introduction 1-1
Page 12
A
A
Product Description (Continued)
Lake Shore Model 331 Temperature Controller User’s Manual
Sensor inputs for both versions of the Model 331 are factory configured and compatible with either
diode/RTDs or thermocouple sensors. The purchaser’s choice of two diode/RTD inputs, one diode/RTD
input and one thermocouple input, or two thermocouple inputs must be specified at time of order and
cannot be reconfigured in the field. Software selects appropriate excitation current and signal gain
levels when sensor type is entered via the instrument front panel.
Temperature Control
The Model 331E offers one and the Model 331S offers two proportional-integral-derivative (PID) control
loops. A PID control algorithm calculates control output based on temperature setpoint and feedback
from the control sensor. Wide tuning parameters accommodate most cryogenic cooling systems and
many small high-temperature ovens. Control output is generated by a high-resolution digital-to-analog
converter for smooth continuous control. The user can set the PID values or the Autotuning feature of
the Model 331 can automate the tuning process.
Heater output for Model 331S and Model 331E is a well-regulated variable DC current source. Heater
output is optically isolated from other circuits to reduce interference and ground loops. Heater output
can provide up to 50 W of continuous power to a resistive heater load, and includes two lower ranges
for systems with less cooling power. Heater output is short-circuit protected to prevent instrument
damage if the heater load is accidentally shorted.
The setpoint ramp feature allows smooth continuous changes in setpoint and can also make the
approach to a setpoint temperature more predictable. The zone feature can automatically change
control parameter values for operation over a large temperature range. Values for ten different
temperature zones can be loaded into the instrument, which will select the next appropriate value on
setpoint change.
Interface
The Model 331 is available with both parallel (IEEE-488, 331S only) and serial (RS-232C) computer
interfaces. In addition to data gathering, nearly every function of the instrument can be controlled via
computer interface. Also included is a Model 330 command emulation mode that makes the Model 331
interchangeable with the older Model 330 in software controlled systems.
Each input has a high and low alarm which offer latching and non-latching operation. The two relays on
the Model 331S can be used in conjunction with the alarms to alert the operator of a fault condition or
perform simple on-off control. Relays can be assigned independently to any alarm or be operated
manually.
When not being used for temperature control, the loop 2 control output can be used as an analog
voltage output. It can be configured to send a voltage proportional to temperature to a strip-chart
recorder or data acquisition system. The user may select the scale and data sent to the output,
including temperature, sensor units, or linear equation results. Under manual control, the analog
voltage output can also serve as a voltage source for other applications.
Interface Features of Model 331S and Model 331E
Feature 331S 331E
Numeric keypad
Front panel curve entry
larms
RS-232C interface
IEEE-488 interface
Second control loop
nalog voltage output
Two relays
1-2 Introduction
Page 13
Lake Shore Model 331 Temperature Controller User’s Manual
Line input assembly
Serial (RS-232C) I/O (DTE)
Heater output
IEEE-488 interface
Terminal block (for relays and analog output)
Sensor input connectors
Figure 1-1. Model 331S Rear Panel Connections
Configurable Display
Both versions of the Model 331 include a bright vacuum fluorescent display that simultaneously
displays up to four readings. Display data includes input and source annunciators for each reading. All
four display locations can be configured by the user. Data from either input may be assigned to any of
the four locations; the user’s choice of temperature, sensor units, maximum, minimum, or linear
equation results can be displayed. Heater range and control output as current or power can also be
continuously displayed for immediate feedback on control operation.
Normal (Default) Display Configuration
The display provides four reading locations. Readings from each input and the control setpoint can be
expressed in any combination of temperature or sensor units, with heater output expressed as a
percent of full scale current or power.
Flexible Configuration
Reading locations can be configured by the user to meet application needs. The character preceding
the reading indicates input A or B or setpoint S. The character following the reading indicates
measurement units or the math function in use.
Curve Entry
The Model 331 display offers the flexibility to support curve, SoftCal™, and zone entry. Curve entry
may be performed accurately and to full resolution via the display and keypad as well as computer
interface.
Introduction 1-3
Page 14
Lake Shore Model 331 Temperature Controller User’s Manual
1.1 SENSOR SELECTION
Table 1-1. Sensor Temperature Range
Model Useful Range Magnetic Field Use
Diodes Silicon Diode DT-670-SD 1.4 K to 500 K
Silicon Diode DT-670E-BR 30 K to 500 K
Silicon Diode DT-414 1.4 K to 375 K
Silicon Diode DT-421 1.4 K to 325 K
Silicon Diode DT-470-SD 1.4 K to 500 K
Silicon Diode DT-471-SD 10 K to 500 K
GaAlAs Diode TG-120-P 1.4 K to 325 K
GaAlAs Diode TG-120-PL 1.4 K to 325 K
GaAlAs Diode TG-120-SD 1.4 K to 500 K
Positive
Temperature
Coefficient RTDs
100 Ω Platinum
100 Ω Platinum
Rhodium-Iron RF-800-4 1.4 K to 500 K
PT-102/3 14 K to 873 K
PT-111 14 K to 673 K
Rhodium-Iron RF-100T/U 1.4 K to 325 K
Negative
Temperature
Coefficient
RTDs2
Cernox™ CX-1010 2 K to 325 K5
Cernox™ CX-1030-HT 3.5 K to 420 K
Cernox™ CX-1050-HT 4 K to 420 K
Cernox™ CX-1070-HT 15 K to 420 K3
Cernox™ CX-1080-HT 50 K to 420 K3
T ≥ 60 K & B ≤ 3 T
T ≥ 60 K & B ≤ 3 T
T ≥ 60 K & B ≤ 3 T
T ≥ 60 K & B ≤ 3 T
T ≥ 60 K & B ≤ 3 T
T ≥ 60 K & B ≤ 3 T
T > 4.2 K & B ≤ 5 T
T > 4.2 K & B ≤ 5 T
T > 4.2 K & B ≤ 5 T
T > 40 K & B ≤ 2.5 T
T > 40 K & B ≤ 2.5 T
T > 77 K & B ≤ 8 T
T > 77 K & B ≤ 8 T
T > 2 & B ≤ 19 T
3,6
T > 2 & B ≤ 19 T
3,6
T > 2 & B ≤ 19 T
T > 2 & B ≤ 19 T
T > 2 & B ≤ 19 T
Germanium GR-200A/B-1000 2.2 K to 100 K4 Not Recommended
Germanium GR-200A/B-1500 2.6 K to 100 K4 Not Recommended
Germanium GR-200A/B-2500 3.1 K to 100 K4 Not Recommended
Carbon-Glass CGR-1-500 4 K to 325 K5
Carbon-Glass CGR-1-1000 5 K to 325 K5
Carbon-Glass CGR-1-2000 6 K to 325 K5
Rox™ RX-102A 1.4 K to 40 K5
T > 2 K to ≤ 19 T
T > 2 K to ≤ 19 T
T > 2 K to ≤ 19 T
T > 2 K to ≤ 10 T
Thermocouples Type K 9006-006 3.2 K to 1505 K Not Recommended
Type E 9006-004 3.2 K to 934 K Not Recommended
Chromel-AuFe 0.07% 9006-002 1.2 K to 610 K Not Recommended
2
Single excitation current may limit the low temperature range of NTC resistors.
3
Non-HT version maximum temperature: 325 K.
4
Low temperature limited by input resistance range.
5
Low temperature specified with self-heating error: ≤5 mK.
6
Low temperature specified with self-heating error: ≤12 mK.
Silicon diodes are the best choice for general cryogenic use from 1.4 K to above room temperature.
Diodes are economical to use because they follow a standard curve and are interchangeable in many
applications. They are not suitable for use in ionizing radiation or magnetic fields.
Cernox™ thin-film RTDs offer high sensitivity and low magnetic field-induced errors over the 2 K to
420 K temperature range. Cernox sensors require calibration.
Platinum RTDs offer high uniform sensitivity from 30 K to over 800 K. With excellent reproducibility,
they are useful as thermometry standards. They follow a standard curve above 70 K and are
interchangeable in many applications.
1-4 Introduction
Page 15
Lake Shore Model 331 Temperature Controller User’s Manual
Table 1-2. Typical Sensor Performance
Temperature
Accuracy
Example Lake
Shore Sensor
Silicon Diode DT-670-SD-13
with 1.4H
calibration
Electronic
Accuracy:
Temperature
Equivalents
Temp
Nominal
Resistance/
Voltage
Typical Sensor
Sensitivity
7
Measurement
Resolution:
Temperature
Equivalents
1.4 K 1.644 V -12.49 mV/K 0.8 mK ±13 mK ±25 mK ±1.6 mK
77 K 1.028 V -1.73 mV/K 5.8 mK ±76 mK ±98 mK ±11.6 mK
300 K 0.5597 V -2.3 mV/K 4.4 mK ±47 mK ±79 mK ±8.8 mK
including
Electronic
Accuracy,
CalCurve™, and
Calibrated
500 K 0.0907 V -2.12 mV/K 4.8 mK ±40 mK ±90 mK ±9.6 mK
Silicon Diode DT-470-SD-13
with 1.4H
calibration
1.4 K 1.6981 V -13.1 mV/K 0.8 mK ±13 mK ±25 mK ±1.6 mK
77 K 1.0203 V -1.92 mV/K 5.2 mK ±69 mK ±91 mK ±10.4 mK
300 K 0.5189 V -2.4 mV/K 4.2 mK ±45 mK ±77 mK ±8.4 mK
475 K 0.0906 V -2.22 mV/K 4.6 mK ±39 mK ±89 mK ±9.2 mK
GaAlAs
Diode
TG-120-SD
with 1.4H
calibration
1.4 K 5.391 V -97.5 mV/K 0.2 mK ±7 mK ±19 mK ±0.4 mK
77 K 1.422 V -1.24 mV/K 16.2 mK ±180 mK ±202 mK ±32.4 mK
300 K 0.8978 V -2.85 mV/K 7 mK ±60 mK ±92 mK ±14 mK
475 K 0.3778 V -3.15 mV/K 6.4 mK ±38 mK ±88 mK ±12.8 mK
100 Ω
Platinum
PT-103 with
1.4J calibration
RTD 500 Ω
Full Scale
Cernox™ CX-1050-SD-
HT
9
with 4M
calibration
Germanium GR-200A-1000
with 1.4D
calibration
CarbonGlass
CGR-1-2000
with 4L
calibration
Thermo-
Type K 75 K -5862.9 µV 15.6 µV/K 26 mK ±0.25 K10
couple
50mV
30 K
77 K
300 K
500 K
4.2 K
77 K
300 K
420 K
2 K
4.2 K
10 K
100 K
4.2 K
77 K
300 K
3.660 Ω 0.191 Ω/K
20.38 Ω 0.423 Ω/K
110.35 Ω 0.387 Ω/K
185.668 Ω 0.378 Ω/K
3507.2 Ω -1120.8 Ω/K
205.67 Ω -2.4116 Ω/K
59.467 Ω -0.1727 Ω/K
45.030 Ω -0.0829 Ω/K
6674 Ω -9930 Ω/K
1054 Ω -526 Ω/K
170.9 Ω -38.4 Ω/K
2.257 Ω -0.018 Ω/K
2260 Ω -2060 Ω/K
21.65 Ω -0.157 Ω/K
11.99 Ω -0.015 Ω/K
300 K 1075.3 µV 40.6 µV/K 10 mK ±0.038 K10 ±20 mK
600 K 13325 µV 41.7 µV/K 10 mK ±0.184 K10 ±20 mK
10.5 mK ±23 mK ±33 mK ±21 mK
4.8 mK ±15 mK ±27 mK ±9.6 mK
5.2 mK ±39 mK ±62 mK ±10.4 mK
5.3 mK ±60 mK ±106 mK ±10.6 mK
36 µK ±1.4 mK ±6.4 mK ±72 µK
16.6 mK ±76 mK ±92 mK ±33.2 mK
232 mK ±717 mK ±757 mK ±464 mK
483 mK ±1.42 K ±1.49 K ±966 mK
4 µK ±0.3 mK ±4.3 mK ±8 µK
76 µK ±1 mK ±5 mK ±152 µK
1 mK ±4.4 mK ±9.4 mK ±2 mK
2.22 K ±5.61 K ±5.626 K ±4.44 K
20 µK ±0.5 mK ±4.5 mK ±40 µK
255 mK ±692 mK ±717 mK ±510 mK
2.667 K ±7 K ±7.1 K ±5.344 K
Calibration not
available from
Lake Shore
1505 K 49998.3 µV 36.006 µV/K 12 mK ±0.73 K10 ±24 mK
7
Typical sensor sensitivities were taken from representative calibrations for the sensor listed
8
Control stability of the electronics only, in an ideal thermal system
9
Non-HT version maximum temperature: 325 K
10
Accuracy specification does not include errors from room temperature compensation
Sensor
Electronic
Control
8
Stability
Temperature
:
Equivalents
±52 mK
Introduction 1-5
Page 16
Lake Shore Model 331 Temperature Controller User’s Manual
1.2 SPECIFICATIONS
Table 1-3. Input Specifications
Diode negative 0 V to 2.5 V 10 µA ±0.05%
PTC RTD positive
NTC RTD negative
Sensor
Temperature
Coefficient
Input Range Excitation Current
negative 0 V to 7.5 V 10 µA ±0.05%
1 mA14
1 mA14
10 µA ±0.05%14
positive
0 Ω to 500 Ω
0 Ω to 5000 Ω
0 Ω to 7500 Ω
12,13
12,13
Thermocouple positive ±25 mV NA 1 µV 0.4 µV ±1 µV ±0.05% of rdg15 ±0.8 µV
positive ±50 mV NA 1 µV 0.4 µV ±1 µV ±0.05% of rdg15 ±0.8 µV
11
Control stability of the electronics only, in an ideal thermal system
12
Current source error has negligible effect on measurement accuracy
13
Diode input excitation can be set to 1 mA – refer to Paragraph 4.4.2
14
Current source error is removed during calibration
15
Accuracy specification does not include errors from room temperature compensation
Display
Resolution
100 µV 10 µV ±80 µV ±0.005% of rdg ±20 µV
100 µV 20 µV ±80 µV ±0.01 % of rdg ±40 µV
10 mΩ 2 mΩ ±0.004 Ω ±0.01% of rdg ±4 mΩ
100 mΩ 20 mΩ ±0.04 Ω ±0.02% of rdg ±40 mΩ
100 mΩ 40 mΩ ±0.1 Ω ±0.04% of rdg ±80 mΩ
Measurement
Resolution
Electronic Accuracy
Electronic
Control
Stability
11
Thermometry
Number of inputs 2
Input configuration Each input is factory configured for either diode/RTD or thermocouples
Isolation Sensor inputs optically isolated from other circuits but not each other
A/D resolution 24-bit
Input accuracy Sensor dependent – refer to Input Specifications table
Measurement resolution Sensor dependent – refer to Input Specifications table
Maximum update rate 10 readings/s on each input (except 5 readings/s on input A when configured
as thermocouple)
User curves Room for twenty 200-point CalCurves™ or user curves
SoftCal™ Improves accuracy of DT-470 diode to ±0.25 K from 30 K to 375 K; improves
accuracy of Platinum RTDs to ±0.25 K from 70 K to 325 K – stored as user
curves
Math Maximum, Minimum, and Linear Equation (Mx + B) or M(x+B)
Filter Averages 2 to 64 input readings
Table 1-4. Sensor Input Configuration
Diode/RTD Thermocouple
Measurement type 4-lead differential 2-lead, room temperature compensated
Excitation
Constant current with current reversal for
RTDs
NA
Diodes: Silicon, GaAlAs RTDs: 100 Ω
Supported sensors
Platinum, 1000 Ω Platinum, Germanium,
Most thermocouple types
Carbon-Glass, Cernox™, and Rox™
Standard curves
DT-470, DT-500D, DT-670, PT-100, PT-
1000, RX-102A, RX-202A
Type E, Type K, Type T, AuFe 0.07%
vs. Cr, AuFe 0.03% vs. Cr
Input connector 6-pin DIN Ceramic isothermal block
1-6 Introduction
Page 17
Specifications (Continued)
Lake Shore Model 331 Temperature Controller User’s Manual
Control
Control loops Two on 331S, one on 331E
Control type Closed loop digital PID with manual heater output, or open loop
Tuning Autotune (one loop at a time), PID, PID zones
Control stability Sensor dependent – to 2× measurement resolution
(in an ideal thermal system)
PID control parameters
Proportional (gain) 0 to 1000 with 0.1 setting resolution
Integral (reset) 1 to 1000 (1000/s) with 0.1 setting resolution
Derivative (rate) 1 to 200% with 1% resolution
Manual output 0 to 100% with 0.01% setting resolution
Zone control 10 temperature zones with P, I, D, manual heater out, and heater range
Setpoint ramping 0.1 K/min to 100 K/min
Safety limits Curve temperature, power up heater off, short circuit protection
Table 1-5. Heater Output
Loop 1 Loop 2
Heater output type Variable DC current source Variable DC voltage source
Heater output D/A resolution 18-bit 16-bit
Max heater power 50 W 1 W
Max heater output current 1 A 0.1 A
Heater output compliance 50 V 10 V
Heater output ranges 3 decade steps in power 1
Heater load type Resistive Resistive
Heater load range
Heater load for max power
Heater noise (<1 kHz) RMS 50 µV + 0.01% of output voltage <0.3 mV
Isolation
Heater connector Dual banana Detachable terminal block
10 Ω to 100 Ω recommended 100 Ω minimum
50 Ω 100 Ω
Optical isolation between output and
other circuits
None
Table 1-6. Loop 1 Full Scale Heater Power at Typical Resistance
Heater Resistance Heater Range Heater Power
10 Ω
25 Ω
50 Ω
Low
Med
High
Low
Med
High
Low
Med
High
100 mW
1 W
10 W
250 mW
2.5 W
25 W
500 mW
5 W
50 W
Introduction 1-7
Page 18
Specifications (Continued)
Lake Shore Model 331 Temperature Controller User’s Manual
Front Panel
Display 2 line by 20 character, 9 mm character height, vacuum fluorescent
display
Number of reading displays 1 to 4
Display units K, °C, V, mV, Ω
Reading source Temperature, sensor units, max, min, and linear equation
Display update rate All readings twice per s
Temp display resolution 0.001° from 0° to 99.999°, 0.01° from 100° to 999.99°,
0.1° above 1000°
Sensor units display resolution Sensor dependent to 5 digits
Other displays Setpoint, Heater Range, and Heater Output (user selected)
Setpoint setting resolution Same as display resolution (actual resolution is sensor dependent)
Heater output display Numeric display in percent of full scale for power or current
Heater output resolution 1%
Display annunciators Control Input, Remote, Alarm, Tuning, Ramp, Max, Min, Linear
Keypad 20 full travel keys, numeric and specific functions
Front panel features Front panel curve entry, display brightness control, keypad lock-out
Interface
IEEE-488 interface (331S)
Features SH1, AH1, T5, L4, SR1, RL1, PP0, DC1, DT0, C0, E1
Reading rate To 10 readings per s on each input
Software support LabVIEW™ driver (consult factory for availability)
Serial interface
Electrical format RS-232C
Max baud rate 9600 baud
Connector 9-pin D-sub
Reading rate To 10 readings/s on each input (at 9600 baud)
Special interface features Model 330 command emulation mode
Alarms
Number 4, high and low for each input
Data source Temperature, Sensor Units, Linear Equation
Settings Source, High Setpoint, Low Setpoint, Deadband, Latching or Non-
Latching, Audible On/Off
Actuators Display annunciator, beeper, relays
Relays (331S)
Number 2
Contacts Normally Open (NO), Normally Closed (NC), and Common (C)
Contact rating 30 VDC at 5 A
Operation Activate relays on high, low, or both alarms for either input or manual
Connector Detachable terminal block
Analog voltage output (331S)
Scale User selected
Update rate 10 readings per s
Data source Temperature, Sensor Units, Linear Equation
Settings Input, source, top of scale, bottom of scale, or manual
Range ±10 V
Resolution 0.3 mV
Accuracy ±2.5 mV
Min load resistance 100 Ω (short circuit protected)
1-8 Introduction
Page 19
Specifications (Continued)
Lake Shore Model 331 Temperature Controller User’s Manual
General
Ambient temperature 15 °C to 35 °C at rated accuracy, 10 °C to 40 °C at reduced accuracy
Power requirement 100, 120, 220, 240 VAC, (+6%, -10%), 50 or 60 Hz, 120 VA
Size 216 mm W × 89 mm H × 368 mm D (8.5 in × 3.5 in × 14.5 in), half rack
Weight 4.8 kg (10.5 lb)
Approval CE mark
Product Configuration
Part Number Description (Input configuration cannot be chang ed in the field)
Standard Temperature Controllers, all features included:
331S Two Diode/Resistor Inputs
331S-T1 One Diode/Resistor, One Thermocouple Input
331S-T2 Two Thermocouple Inputs
Economy Temperature Controllers, all features of the 331S except does not include the following:
IEEE-488, relays, analog voltage output, second control loop.
331E Two Diode/Resistor Inputs
331E-T1 One Diode/Resistor, One Thermocouple Input
331E-T2 Two Thermocouple Inputs
Refer to Chapter 7 of this manual for a complete description of Model 331 options and accessories.
Specifications subject to change without notice.
1.3 SAFETY SUMMARY
Observe these general safety precautions during all phases of instrument operation, service, and
repair. Failure to comply with these precautions or with specific warnings elsewhere in this manual
violates safety standards of design, manufacture, and intended instrument use. Lake Shore
Cryotronics, Inc. assumes no liability for Customer failure to comply with these requirements.
The Model 331 protects the operator and surrounding area from electric shock or burn, mechanical
hazards, excessive temperature, and spread of fire from the instrument. Environmental conditions
outside of the conditions below may pose a hazard to the operator and surrounding area.
• Indoor use.
• Altitude to 2000 meters.
• Temperature for safe operation: 5 °C to 40 °C.
• Maximum relative humidity: 80% for temperature up to 31 °C decreasing linearly to 50% at 40 °C.
• Power supply voltage fluctuations not to exceed ±10% of the nominal voltage.
• Overvoltage category II.
• Pollution degree 2.
Ground The Instrument
To minimize shock hazard, the instrument is equipped with a three-conductor AC power cable. Plug the
power cable into an approved three-contact electrical outlet or use a three-contact adapter with the
grounding wire (green) firmly connected to an electrical ground (safety ground) at the power outlet.
The power jack and mating plug of the power cable meet Underwriters Laboratories (UL) and
International Electrotechnical Commission (IEC) safety standards.
Introduction 1-9
Page 20
Safety Summary (Continued)
Lake Shore Model 331 Temperature Controller User’s Manual
Ventilation
The instrument has ventilation holes in its side covers. Do not block these holes when the instrument is
operating.
Do Not Operate In An Explosive Atmosphere
Do not operate the instrument in the presence of flammable gases or fumes. Operation of any electrical
instrument in such an environment constitutes a definite safety hazard.
Keep Away From Live Circuits
Operating personnel must not remove instrument covers. Refer component replacement and internal
adjustments to qualified maintenance personnel. Do not replace components with power cable
connected. To avoid injuries, always disconnect power and discharge circuits before touching them.
Do Not Substitute Parts Or Modify Instrument
Do not install substitute parts or perform any unauthorized modification to the instrument. Return the
instrument to an authorized Lake Shore Cryotronics, Inc. representative for service and repair to ensure
that safety features are maintained.
Cleaning
Do not submerge instrument. Clean only with a damp cloth and mild detergent. Exterior only.
1.4 SAFETY SYMBOLS
1-10 Introduction
Page 21
Lake Shore Model 331 Temperature Controller User’s Manual
CHAPTER 2
COOLING SYSTEM DESIGN
2.0 GENERAL
Selecting the proper cryostat or cooling source is probably the most important decision in designing a
temperature control system. The cooling source defines minimum temperature, cool-down time, and
cooling power. (Information on choosing a cooling source is beyond the scope of this manual.) This
chapter provides information on how to get the best temperature measurement and control from cooling
sources with proper setup including sensor and heater installation.
Chapter 2 contains the following major topics. Temperature sensor selection is covered in
Paragraph 2.1. Calibrated sensors are covered in Paragraph 2.2. Sensor installation is covered in
Paragraph 2.3. Heater selection and installation is covered in Paragraph 2.4. Considerations for good
control are covered in Paragraph 2.5. PID Control is covered in Paragraph 2.6. Manual Tuning is
covered in Paragraph 2.7. AutoTuning is covered in Paragraph 2.8. Finally, Zone Tuning is covered in
Paragraph 2.9.
2.1 TEMPERATURE SENSOR SELECTION
This section attempts to answer some of the basic questions concerning temperature sensor selection.
Additional useful information on temperature sensor selection is available in the Lake Shore
Temperature Measurement and Control Catalog. The catalog has a large reference section that
includes sensor characteristics and sensor selection criteria.
2.1.1 Temperature Range
Several important sensor parameters must be considered when choosing a sensor. The first is
temperature range. The experimental temperature range must be known when choosing a sensor.
Some sensors can be damaged by temperatures that are either too high or too low. Manufacturer
recommendations should always be followed.
Sensor sensitivity is also dependent on temperature and can limit the useful range of a sensor. It is
important not to specify a range larger than necessary. If an experiment is being done at liquid helium
temperature, a very high sensitivity is needed for good measurement resolution at that temperature.
That same resolution may not be required to monitor warm up to room temperature. Two different
sensors may be required to tightly cover the range from helium to room temperature, but lowering the
resolution requirement on warm up may allow a less expensive, one sensor solution.
Another thing to consider when choosing a temperature sensor is that instruments like the Model 331
are not able to read some sensors over their entire temperature range. Lake Shore sells calibrated
sensors that operate down to 50 millikelvin (mK), but the Model 331 is limited to above 1 K in its
standard configuration.
2.1.2 Sensor Sensitivity
Temperature sensor sensitivity is a measure of how much a sensor signal changes when the
temperature changes. It is an important sensor characteristic because so many measurement
parameters are related to it. Resolution, accuracy, noise floor, and even control stability depend on
sensitivity. Many sensors have different sensitivities at different temperatures. For example, a
platinum sensor has good sensitivity at higher temperatures but has limited use below 30 kelvin (K)
because its sensitivity drops sharply. It is difficult to determine if a sensor has adequate sensitivity
over the experimental temperature range. This manual has specifications (Table 1-3) that include
sensor sensitivity translated into temperature resolution and accuracy at different points. This is
typical sensor response and can be used as a guide when choosing a sensor to be used with the
Model 331.
Cooling System Design 2-1
Page 22
Lake Shore Model 331 Temperature Controller User’s Manual
2.1.3 Environmental Conditions
The experimental environment is also important when choosing a sensor. Environmental factors such
as high vacuum, magnetic field, corrosive chemicals, or even radiation can limit the use of some
types of sensors. Lake Shore has devoted much time to developing sensor packages that withstand
the temperatures, vacuum levels, and bonding materials found in typical cryogenic cooling systems.
Experiments done in magnetic fields are becoming very common. Field dependence of temperature
sensors is an important selection criteria for sensors used in these experiments. This manual briefly
qualifies the field dependence of most common sensors in the specifications (Table 1-3). Detailed
field dependence tables are included in the Lake Shore Temperature Measurement and Control
Catalog. When available, specific data on other environmental factors is also included in the catalog.
2.1.4 Measurement Accuracy
Temperature measurements have several sources of error that reduce accuracy. Be sure to account
for errors induced by both the sensor and the instrumentation when computing accuracy. The
instrument has measurement error in reading the sensor signal and error in calculating a temperature
using a temperature response curve. Error results from the sensor being compared to a calibration
standard and the temperature response of a sensor will shift with time and with repeated thermal
cycling (from very cold temperatures to room temperature). Instrument and sensor makers specify
these errors but there are things a user can do to maintain good accuracy. For example, choose a
sensor that has good sensitivity in the most critical temperature range, as sensitivity can minimize the
effect of most error sources. Install the sensor properly following guidelines in Paragraph 2.3. Have
the sensor and instrument periodically recalibrated, or in some other way null the time dependent
errors. Use a sensor calibration that is appropriate for the accuracy requirement.
2.1.5 Sensor Package
Many types of sensors can be purchased in different packages. Some types of sensors can even be
purchased as bare chips; without any package. A sensor package generally determines its size,
thermal and electrical contact to the outside, and sometimes limits temperature range. When different
packages are available for a sensor, the user should consider the mounting surface for the sensor
and how leads will be heat sinked when choosing.
2.2 CALIBRATED SENSORS
There can sometimes be confusion in the difficult task of choosing the right sensor, getting it calibrated,
translating the calibration data into a temperature response curve that the Model 331 can understand,
then getting the curve loaded into the instrument. Lake Shore provides a variety of calibration and curve
loading services to fit different accuracy requirements and budgets.
2.2.1 Traditional Calibration
Calibration is done by comparing a sensor with an unknown temperature response to an accepted
standard. Lake Shore temperature standards are traceable to the U.S. National Institute of Standards
and Testing (NIST) or the National Physical Laboratory in Great Britain. These standards allow Lake
Shore to calibrate sensors from 50 mK to above room temperature. Calibrated sensors are more
expensive than uncalibrated sensors of the same type because of the labor and capitol equipment
used in the process.
This type of calibration provides the most accurate temperature sensors available from Lake Shore.
Errors from sensor calibration are almost always smaller than the error contributed by the Model 331.
The Lake Shore Temperature Measurement and Control Catalog has complete accuracy
specifications for calibrated sensors.
2-2 Cooling System Design
Page 23
Traditional Calibration (Continued)
Lake Shore Model 331 Temperature Controller User’s Manual
Calibrated sensors include the measured test data printed and plotted, the coefficients of a
Chebychev polynomial that has been fitted to the data, and two tables of data points to be used as
interpolation tables. Both interpolation tables are optimized to allow accurate temperature conversion.
The smaller table, called a breakpoint interpolation table, is sized to fit into instruments like the Model
331 where it is called a temperature response curve. Getting a curve into a Model 331 may require a
CalCurve™ described below or hand entering through the instrument front panel.
It is important to look at instrument specifications before ordering calibrated sensors. A calibrated
sensor is required when a sensor does not follow a standard curve if the user wishes to display in
temperature. Otherwise the Model 331 will operate in sensor units like ohms or volts. The Model 331
may not work over the full temperature range of some sensors. The standard inputs in are limited to
operation above 1 K even with sensors that can be calibrated to 50 mK.
2.2.2 SoftCal™
SoftCal is a good solution for applications that do not require the accuracy of a traditional calibration.
The SoftCal algorithm uses the well behaved nature of sensors that follow a standard curve to
improve the accuracy of individual sensors. A few known temperature points are required to perform
SoftCal.
Lake Shore sells SoftCal calibrated sensors that include both the large interpolation table and the
smaller breakpoint interpolation table. A CalCurve may be required to get the breakpoint table into a
Model 331 where it is called a temperature response curve. Refer to Paragraph 2.2.4.
The Model 331 can also perform a SoftCal calibration. The user must provide one, two, or three
known temperature reference points. The range and accuracy of the calibration is based on these
points. Refer to Paragraph 5.3.
2.2.3 Standard Curves
Some types of sensors behave in a very predictable manner and a standard temperature response
curve can be created for them. Standard curves are a convenient and inexpensive way to get
reasonable temperature accuracy. Sensors that have a standard curve are often used when
interchangeability is important. Some individual sensors are selected for their ability to match a
published standard curve and sold at a premium, but in general these sensors do not provide the
accuracy of a calibrated sensor. For convenience, the Model 331 has several standard curves
included in firmware.
2.2.4 CalCurve™
The CalCurve service provides the user with a convenient way get the temperature response curve
from Lake Shore calibrated sensors into instruments like the Model 331. It can be performed at the
factory when calibrated sensors and instruments are ordered together. The factory installed CalCurve
option is Model 8001-331 and should be ordered with the calibrated sensor. A CalCurve can be done
in the field when additional or replacement sensors are installed. Curve data is loaded into some type
of non-volatile memory that is installed into the instrument by the user. In the case of the Model 331,
the curve is loaded into a non-volatile memory which can be installed into the instrument. The field
installed version is a Model 8002-05-331 and should be ordered with the calibrated sensor.
Customers that have a PC-compatible computer with an RS-232C or IEEE-488 interface have
another option. The Model 8000 is included with the calibrated sensor and can be loaded by the user.
Cooling System Design 2-3
Page 24
Lake Shore Model 331 Temperature Controller User’s Manual
Regarding accuracy, there are 3
things that can be done with a
temperature sensor:
Lake Shore Silicon Diode
Temperature Sensor
Standard
Standard sensors are interchangeable within published tolerance
bands. Below is a list of Standard
Curve 10 DT-470 Tolerance
(Accuracy) Bands.
BandBand
2 K* -2 K* 100 K100 K
11 ±0.25 K ±0.5 K ±1.0 K
11A ±0.25 K ±1% of Temp.
12 ±0.5 K ±1.0 K ±2.0 K
12A ±0.5 K ±1% of Temp.
13 ±1 K ±1% of Temp.
* Temperatures down to 1.4 K only with
a Precision Calibrated Sensor.
To increase accuracy, perform a
SoftCal with the controller and
sensor. After sensor calibration, the
custom sensor curve replaces the
standard Curve 10.
100 K -100 K -
305 K305 K
305 K -305 K -
375 K375 K
SoftCal
Calibration
A Lake Shore SoftCal applies only to
Silicon Diodes. A 2-point SoftCal
takes data points at 77.35 K and
305 K. A 3-point SoftCal takes data
points at 4.2 K, 77.35 K, and 305 K.
Typical 2-Point AccuracyTypical 2-Point Accuracy
±1.0 K 2 K to <30 K
±0.25 K 30 K to <60 K
±0.15 K 60 K to <345 K
±0.25 K 345 K to <375 K
±1.0 K 375 K to 475 K
Typical 3-Point AccuracyTypical 3-Point Accuracy
±0.5 K 2 K to <30 K
±0.25 K 30 K to <60 K
±0.15 K 60 K to <345 K
±0.25 K 345 K to <375 K
±1.0 K 375 K to 475 K
Enter voltages at the 2 or 3 data
points into SoftCal capable
controllers. A calibration report
comes with the sensor.
Precision
Calibration
Lake Shore precision calibrates
most sensor types by taking up to
99 data points concentrated in
areas of interest. Typical silicon
diode calibration accuracy is listed
below.
Temp. Typical Maximum
<10 K 12 mK 20 mK
10 K 12 mK 20 mK
20 K 15 mK 25 mK
30 K 25 mK 45 mK
50 K 30 mK 55 mK
100 K 25 mK 50 mK
300 K 25 mK 50 mK
340 K 100 mK
480 K 100 mK
A curve is fitted to these points.
A detailed report including Raw
Temperature Data, Polynomial
Fits, and Interpolation Tables
comes with the sensor.
A Precision Option can be
generated for either SoftCal
or the Precision Calibration:
8001-331
Factory installs a NOVRAM
with Precision Option
breakpoint pairs loaded in it.
C-331-2-1.eps
Users download Precision
Option breakpoint pairs in ACSII
format from a floppy disk.
Precision
Option
- or -
8000 8002-05-331
User calculates break-
points and manually enters
data into the controller
Users install a NOVRAM
with Precision Option
breakpoint pairs loaded in it.
Figure 2-1. Silicon Diode Sensor Calibrations and CalCurve
2-4 Cooling System Design
Page 25
Lake Shore Model 331 Temperature Controller User’s Manual
2.3 SENSOR INSTALLATION
This section highlights some of the important elements of proper sensor installation. For more detailed
information, Lake Shore sensors are shipped with installation instructions that cover that specific sensor
type and package. The Lake Shore Temperature Measurement and Control Catalog includes an
installation section as well. To further help users properly install sensors, Lake Shore offers a line of
Cryogenic Accessories. Many of the materials discussed are available through Lake Shore and can be
ordered with sensors or instruments.
2.3.1 Mounting Materials
Choosing appropriate mounting materials is very important in a cryogenic environment. The high
vacuum used to insulate cryostats is one source of problems. Materials used in these applications
should have a low vapor pressure so they do not evaporate or out-gas and spoil the vacuum
insulation. Metals and ceramics do not have this problem but greases and varnishes must be
checked. Another source of problems is the wide extremes in temperature most sensors are exposed
to. The linear expansion coefficient of a materials becomes important when temperature changes are
so large. Never try to permanently bond materials with linear expansion coefficients that differ by
more than three. A flexible mounting scheme should be used or the parts will break apart, potentially
damaging them. The thermal expansion or contraction of rigid clamps or holders could crush fragile
samples or sensors that do not have the same coefficient. Thermal conductivity is a property of
materials that can change with temperature. Do not assume that a heat sink grease that works well at
room temperature and above will do the same job at low temperatures.
2.3.2 Sensor Location
Finding a good place to mount a sensor in an already crowded cryostat is never easy. There are less
problems if the entire load and sample holder are at the same temperature. Unfortunately, this not the
case in many systems. Temperature gradients (differences in temperature) exist because there is
seldom perfect balance between the cooling source and heat sources. Even in a well-controlled
system, unwanted heat sources like thermal radiation and heat conducting through mounting
structures can cause gradients. For best accuracy, sensors should be positioned near the sample, so
that little or no heat flows between the sample and sensor. This may not, however, be the best
location for temperature control as discussed below.
2.3.3 Thermal Conductivity
The ability of heat to flow through a material is called thermal conductivity. Good thermal conductivity
is important in any part of a cryogenic system that is intended to be the same temperature. Copper
and aluminum are examples of metals that have good thermal conductivity, while stainless steel does
not. Non-metallic, electrically-insulating materials like alumina oxide and similar ceramics have good
thermal conductivity, while G-10 epoxy-impregnated fiberglass does not. Sensor packages, cooling
loads, and sample holders should have good thermal conductivity to reduce temperature gradients.
Surprisingly, the connections between thermally conductive mounting surfaces often have very poor
thermal conductivity.
2.3.4 Contact Area
Thermal contact area greatly affects thermal conduction because a larger area has more opportunity
to transfer heat. Even when the size of a sensor package is fixed, thermal contact area can be
improved with the use of a gasket material. A soft gasket material forms into the rough mating surface
to increase the area of the two surfaces that are in contact. Good gasket materials are soft, thin, and
have good thermal conductivity. They must also withstand the environmental extremes. Indium foil
and cryogenic grease are good examples.
Cooling System Design 2-5
Page 26
Lake Shore Model 331 Temperature Controller User’s Manual
2.3.5 Contact Pressure
When sensors are permanently mounted, the solder or epoxy used to hold the sensor act as both
gasket and adhesive. Permanent mounting is not a good solution for everyone because it limits
flexibility and can potentially damage sensors. Much care should be taken not to over heat or
mechanically stress sensor packages. Less permanent mountings require some pressure to hold the
sensor to its mounting surface. Pressure greatly improves the action of gasket material to increase
thermal conductivity and reduce thermal gradients. A spring clamp is recommended so that different
rates of thermal expansion do not increase or decrease pressure with temperature change.
2.3.6 Lead Wire
Different types of sensors come with different types and lengths of electrical leads. In general a
significant length of lead wire must be added to the sensor for proper heat sinking and connecting to
a bulk head connector at the vacuum boundary. The lead wire must be a good electrical conductor,
but should not be a good thermal conductor, or heat will transfer down the leads and change the
temperature reading of the sensor. Small 30 to 40 AWG wire made of an alloy like phosphor bronze is
much better than copper wire. Thin wire insulation is preferred and twisted wire should be used to
reduce the effect of RF noise if it is present. The wire used on the room temperature side of the
vacuum boundary is not critical so copper cable is normally used.
Vacuum Shroud
To Room
Temperature
Refrigerator
Expander
Vacuum Space
Radiation Shield
Dental Floss
Tie-Down
Therm al Anchor
(Bobbin)
-or-
Cryogenic Tape
Refrigerator
Stage
Second
Thermal Anchor
Cryogenic Wire
diameter,
(small
(Bobbin)
large AWG)
Cold Stage and
Sensor
Sample Holder
Drawing
Not To Scale
Optical Window
Heater
(wiring not shown
for clarity)
(If Required)
P-331-2-2.bmp
Figure 2-2. Typical Sensor Installation In A Mechanical Refrigerator
2-6 Cooling System Design
Page 27
Lake Shore Model 331 Temperature Controller User’s Manual
2.3.7 Lead Soldering
When additional wire is soldered to short sensor leads, care must be taken not to overheat the
sensor. A heat sink such as a metal wire clamp or alligator clip will heat sink the leads and protect the
sensor. Leads should be tinned before bonding to reduce the time that heat is applied to the sensor
lead. Solder flux should be cleaned after soldering to prevent corrosion.
2.3.8 Heat Sinking Leads
Sensor leads can be a significant source of error if they are not properly heat sinked. Heat will
transfer down even small leads and alter the sensor reading. The goal of heat sinking is to cool the
leads to a temperature as close to the sensor as possible. This can be accomplished by putting a
significant length of lead wire in thermal contact with every cooled surface between room temperature
and the sensor. Lead wires can be adhered to cold surfaces with varnish over a thin electrical
insulator like cigarette paper. They can also be wound onto a bobbin that is firmly attached to the cold
surface. Some sensor packages include a heat sink bobbin and wrapped lead wires to simplify heat
sinking.
2.3.9 Thermal Radiation
Thermal (black body) radiation is one of the ways heat is transferred. Warm surfaces radiate heat to
cold surfaces even through a vacuum. The difference in temperature between the surfaces is one
thing that determines how much heat is transferred. Thermal radiation causes thermal gradients and
reduces measurement accuracy. Many cooling systems include a radiation shield. The purpose of the
shield is to surround the load, sample, and sensor with a surface that is at or near their temperature
to minimize radiation. The shield is exposed to the room temperature surface of the vacuum shroud
on its outer surface, so some cooling power must be directed to the shield to keep it near the load
temperature. If the cooling system does not include an integrated radiation shield (or one cannot be
easily made), one alternative is to wrap several layers of super-insulation (aluminized Mylar) loosely
between the vacuum shroud and load. This reduces radiation transfer to the sample space.
2.4 HEATER SELECTION AND INSTALLATION
There is a variety of resistive heaters that can be used as the controlled heating source for temperature
control. The mostly metal alloys like nichrome are usually wire or foil. Shapes and sizes vary to permit
installation into different systems.
2.4.1 Heater Resistance and Power
Cryogenic cooling systems have a wide range of cooling power. The resistive heater must be able to
provide sufficient heating power to warm the system. The Model 331 can supply up to 50 W of power
to a heater (if the heater resistance is appropriate). The Model 331 heater output current source has a
maximum output of 1 A, limiting maximum power to:
Max Power (watts) = (1 ampere)2 × Resistance (ohms).
Even though the Model 331 output is a current source, it has a voltage limit (called the compliance
voltage) of 50 V, which also limits maximum power:
Max Power (watts)
(50 volts)
=
Resistance (ohms)
2
.
Both limits are in place at the same time, so the smallest of the two computations gives the maximum
power available to the heater. A heater of 50 Ω allows the instrument to provide its maximum power
of 50 watts. A typical smaller resistance of 25 Ω allows 25 watts of power, while a typical larger
resistance of 100 Ω is limited by compliance voltage to 25 watts. The resistor chosen as a heater
must be able to withstand the power being dissipated in it. Pre-packaged resistors have a power
specification that is usually given for the resistor in free air. This power may need to be derated if
used in a vacuum where convection cooling can not take place and it is not adequately heat sinked to
a cooled surface.
Cooling System Design 2-7
Page 28
2.4.2 Heater Location
For best temperature measurement accuracy the heater should be located so that heat flow between
the cooling power and heater is minimized. For best control the heater should be in close thermal
contact with the cooling power. Geometry of the load can make one or both of these difficult to
achieve. That is why there are several heater shapes and sizes.
2.4.3 Heater Types
Resistive wire like nichrome is the most flexible type of heater available. The wire can be purchased
with electrical insulation and has a predictable resistance per given length. This type of heater wire
can be wrapped around a cooling load to give balanced, even heating of the area. Similar to sensor
lead wire, the entire length of the heater wire should be in good thermal contact with the load to allow
for thermal transfer. Heat sinking also protects the wire from over heating and burning out.
Resistive heater wire is also wound into cartridge heaters. Cartridge heaters are more convenient but
are bulky and more difficult to place on small loads. A typical cartridge is 1/4 inch in diameter and
1 inch long. The cartridge should be snugly held in a hole in the load or clamped to a flat surface.
Heat sinking for good thermal contact is again important.
Foil heaters are thin layers of resistive material adhered to, or screened on to, electrically insulating
sheets. There are a variety of shapes and sizes. The proper size heater can evenly heat a flat surface
or around a round load. The entire active area should be in good thermal contact with the load, not
only for maximum heating effect, but to keep spots in the heater from over heating and burning out.
Lake Shore Model 331 Temperature Controller User’s Manual
2.4.4 Heater Wiring
When wiring inside a vacuum shroud, we recommend using 30 AWG copper wire for heater leads.
Too much heat can leak in when larger wire is used. Heat sinking, similar to that used for the sensor
leads, should be included so that any heat leaking in does not warm the load when the heater is not
running. The lead wires should be twisted to minimize noise coupling between the heater and other
leads in the system. When wiring outside the vacuum shroud, larger gage copper cable can be used,
and twisting is still recommended.
2.5 CONSIDERATION FOR GOOD CONTROL
Most of the techniques discussed above to improve cryogenic temperature accuracy apply to control
as well. There is an obvious exception in sensor location. A compromise is suggested below in
Paragraph 2.5.3 – Two Sensor Approach.
2.5.1 Thermal Conductivity
Good thermal conductivity is important in any part of a cryogenic system that is intended to be at the
same temperature. Most systems begin with materials that have good conductivity themselves, but as
sensors, heaters, sample holders, etc., are added to an ever more crowded space, the junctions
between parts are often overlooked. In order for control to work well, junctions between the elements
of the control loop must be in close thermal contact and have good thermal conductivity. Gasket
materials should always be used along with reasonable pressure.
2.5.2 Thermal Lag
Poor thermal conductivity causes thermal gradients that reduce accuracy and also cause thermal lag
that make it difficult for controllers to do their job. Thermal lag is the time it takes for a change in
heating or cooling power to propagate through the load and get to the feedback sensor. Because the
feedback sensor is the only thing that lets the controller know what is happening in the system, slow
information to the sensor slows the response time. For example, if the temperature at the load drops
slightly below the setpoint, the controller gradually increases heating power. If the feedback
information is slow, the controller puts too much heat into the system before it is told to reduce heat.
The excess heat causes a temperature overshoot, which degrades control stability. The best way to
improve thermal lag is to pay close attention to thermal conductivity both in the parts used and their
junctions.
2-8 Cooling System Design
Page 29
2.5.3 Two-Sensor Approach
There is a conflict between the best sensor location for measurement accuracy and the best sensor
location for control. For measurement accuracy the sensor should be very near the sample being
measured which is away from the heating and cooling sources to reduce heat flow across the sample
and thermal gradients. The best control stability is achieved when the feedback sensor is near both
the heater and cooling source to reduce thermal lag. If both control stability and measurement
accuracy are critical it may be necessary to use two sensors, one for each function. Many
temperature controllers including the Model 331 have two sensor inputs for this reason.
2.5.4 Thermal Mass
Cryogenic designers understandably want to keep the thermal mass of the load as small as possible
so the system can cool quickly and improve cycle time. Small mass can also have the advantage of
reduced thermal gradients. Controlling a very small mass is difficult because there is no buffer to
adsorb small changes in the system. Without buffering, small disturbances can very quickly create
large temperature changes. In some systems it is necessary to add a small amount of thermal mass
such as a copper block in order to improve control stability.
2.5.5 System Nonlinearity
Because of nonlinearities in the control system, a system controlling well at one temperature may not
control well at another temperature. While nonlinearities exist in all temperature control systems, they
are most evident at cryogenic temperatures. When the operating temperature changes the behavior
of the control loop, the controller must be retuned. As an example, a thermal mass acts differently at
different temperatures. The specific heat of the load material is a major factor in thermal mass and
the specific heat of materials like copper change as much as three orders of magnitude when cooled
from 100 K to 10 K. Changes in cooling power and sensor sensitivity are also sources of nonlinearity.
The cooling power of most cooling sources also changes with load temperature. This is very
important when operating at temperatures near the highest or lowest temperature that a system can
reach. Nonlinearities within a few degrees of these high and low temperatures make it very difficult to
configure them for stable control. If difficulty is encountered, it is recommended to gain experience
with the system at temperatures several degrees away from the limit and gradually approach it in
small steps.
Keep an eye on temperature sensitivity. Sensitivity not only affects control stability but it also
contributes to the overall control system gain. The large changes in sensitivity that make some
sensors so useful may make it necessary to retune the control loop more often.
Lake Shore Model 331 Temperature Controller User’s Manual
2.6 PID CONTROL
For closed-loop operation, the Model 331 temperature controller uses a algorithm called PID control.
The control equation for the PID algorithm has three variable terms: proportional (P), integral (I), and
derivative (D). See Figure 2-3. Changing these variables for best control of a system is called tuning.
The PID equation in the Model 331 is:
Heater Output =+ +
where the error (e) is defined as: e = Setpoint – Feedback Reading.
Proportional is discussed in Paragraph 2.6.1. Integral is discussed in Paragraph 2.6.2. Derivative is
discussed in Paragraph 2.6.3. Finally, the manual heater output is discussed in Paragraph 2.6.4.
Cooling System Design 2-9
L
Pe I edt D
M
N
z
af
de
dt
O
P
Q
Page 30
2.6.1 Proportional (P)
The Proportional term, also called gain, must have a value greater than zero for the control loop to
operate. The value of the proportional term is multiplied by the error (e) which is defined as the
difference between the setpoint and feedback temperatures, to generate the proportional contribution
to the output: Output (P) = Pe. If proportional is acting alone, with no integral, there must always be
an error or the output will go to zero. A great deal must be known about the load, sensor, and
controller to compute a proportional setting (P). Most often, the proportional setting is determined by
trial and error. The proportional setting is part of the overall control loop gain, and so are the heater
range and cooling power. The proportional setting will need to change if either of these change.
2.6.2 Integral (I)
In the control loop, the integral term, also called reset, looks at error over time to build the integral
contribution to the output:
Output I PI e dt
=
af a f
By adding the integral to proportional contributions, the error that is necessary in a proportional only
system can be eliminated. When the error is at zero, controlling at the setpoint, the output is held
constant by the integral contribution. The integral setting (I) is more predictable than the gain setting.
It is related to the dominant time constant of the load. As discussed in Paragraph 2.7.3, measuring
this time constant allows a reasonable calculation of the integral setting. In the Model 331, the integral
term is not set in seconds like some other systems. The integral setting can be derived by dividing
1000 by the integral seconds: I
Lake Shore Model 331 Temperature Controller User’s Manual
z
.
setting
= 1000 / I
seconds
.
2.6.3 Derivative (D)
The derivative term, also called rate, acts on the change in error with time to make its contribution to
the output:
Output D PD
()= .
de
dt
By reacting to a fast changing error signal the derivative can work to boost the output when the
setpoint changes quickly, reducing the time it takes for temperature to reach the setpoint. It can also
see the error decreasing rapidly when the temperature nears the setpoint and reduce the output for
less overshoot. The derivative term can be useful in fast changing systems but it is often turned off
during steady state control because it reacts too strongly to small disturbances. The derivative setting
(D) is related to the dominant time constant of the load similar to the I
proportional to I
when used.
setting
2.6.4 Manual Heater Power (MHP) Output
The Model 331 has a control setting that is not a normal part of a PID control loop. Manual Heater
Power (MHP) output can be used for open loop control, meaning feedback is ignored and the heater
output stays at the users manual setting. This is a good way to put constant heating power into a load
when needed. The MHP output term can also be added to the PID output. Some users prefer to set a
power near that necessary to control at a setpoint and let the closed loop make up the small
difference. MHP output is set in percent of full scale current or power for a given heater range.
NOTE: MHP output should be set to 0% when not in use.
and is therefore set
setting
2-10 Cooling System Design
Page 31
Lake Shore Model 331 Temperature Controller User’s Manual
P-331-2-3.bmp
Cooling System Design 2-11
Figure 2-3. Examples of PID Control
Page 32
Lake Shore Model 331 Temperature Controller User’s Manual
2.7 MANUAL TUNING
There has been a lot written about tuning closed loop control systems and specifically PID control
loops. This section does not attempt to compete with control theory experts. It describes a few basic
rules of thumb to help less experienced users get started. This technique will not solve every problem,
but it has worked for many others in the field. This section assumes the user has worked through the
operation sections of this manual, has a good temperature reading from the sensor chosen as a control
sensor, and is operating Loop 1. It is also a good idea to begin at the center of the temperature range of
the cooling system (not close to its highest or lowest temperature). AutoTune (Paragraph 2.8) is
another good place to begin, and do not forget the power of trial and error.
2.7.1 Setting Heater Range
Setting an appropriate heater output range is an important first part of the tuning process. The heater
range should allow enough heater power to comfortably overcome the cooling power of the cooling
system
. If the heater range will not provide enough power, the load will not be able to reach the
setpoint temperature. If the range is set too high, the load may have very large temperature changes
that take a long time to settle out. Delicate loads can even be damaged by too much power.
Often there is little information on the cooling power of the cooling system at the desired setpoint. If
this is the case, try the following: Allow the load to cool completely with the heater off. Set manual
heater power output to 50% while in Open Loop control mode. Turn the heater to the lowest range
and write down the temperature rise (if any). Select the next highest heater range and continue the
process until the load warms up to room temperature. Do not leave the system unattended, the
heater may have to be turned off manually to prevent overheating. If the load never reaches room
temperature, some adjustment may be needed in heater resistance or load.
The list of heater range versus load temperature is a good reference for selection the proper heater
range. It is common for systems to require two or more heater ranges for good control over their full
temperature. Lower heater ranges are normally needed for lower temperature. The Model 331 is of
no use controlling at or below the temperature reached when the heater was off. Many systems can
be tuned to control within a degree or two above that temperature.
2.7.2 Tuning Proportional
The proportional setting is so closely tied to heater range that they can be thought of as fine and
course adjustments of the same setting. An appropriate heater range must be known before moving
on to the proportional setting.
Begin this part of the tuning process by letting the cooling system cool and stabilize with the heater
off. Place the Model 331 in closed loop control mode with manual PID tuning, then turn integral,
derivative and manual output settings off. Enter a setpoint several degrees above the cooling systems
lowest temperature. Enter a low proportional setting of approximately 5 or 10 and then enter the
appropriate heater range as described above. The heater display should show a value greater than
zero and less than 100%. The load temperature should stabilize at a temperature below the setpoint.
If the load temperature and heater meter swing rapidly, the heater range may be set too high and
should be reduced. Very slow changes in load temperature that could be described as drifting are an
indication of a proportional setting that is too low (which is addressed in the next step).
Gradually increase the proportional setting by doubling it each time. At each new setting, allow time
for the temperature of the load to stabilize. As the proportional setting is increased, there should be a
setting in which the load temperature begins a sustained and predictable oscillation rising and falling
in a consistent period of time. See Figure 2-3(a). The goal is to find the proportional value in which
the oscillation begins, do not turn the setting so high that temperature and heater output changes
become violent.
Record the proportional setting and the amount of time it takes for the load change from one
temperature peak to the next. The time is called the oscillation period of the load. It helps describe the
dominant time constant of the load which is used in setting integral. If all has gone well,
appropriate proportional setting is
Figure 2-3(b).
the
one half of the value required for sustained oscillation. See
2-12 Cooling System Design
Page 33
Tuning Proportional (Continued)
Lake Shore Model 331 Temperature Controller User’s Manual
If the load does not oscillate in a controlled manner, the heater range could be set too low. A constant
heater reading of 100% on the display would be an indication of a low range setting. The heater
range could also be too high, indicated by rapid changes in the load temperature or heater output with
a proportional setting of less than 5. There are a few systems that will stabilize and not oscillate with a
very high proportional setting and a proper heater range setting. For these systems, setting a
proportional setting of one half of the highest setting is the best choice.
2.7.3 Tuning Integral
When the proportional setting is chosen and the integral is set to zero (off), the Model 331 controls
the load temperature below the setpoint. Setting the integral allows the Model 331 control algorithm to
gradually eliminate the difference in temperature by integrating the error over time. See Figure 2-3(d).
An integral setting that is too low causes the load to take too long to reach the setpoint. An integral
setting that is too high creates instability and cause the load temperature to oscillate.
Begin this part of the tuning process with the system controlling in proportional only mode. Use the
oscillation period of the load that was measured above in seconds.
the integral setting.
Enter the integral setting into the Model 331 and watch the load temperature
approach the setpoint. If the temperature does not stabilize and begins to oscillate around the
setpoint, the integral setting is too high and should be reduced by one half. If the temperature is
stable but never reaches the setpoint, the integral setting is too low and should be doubled.
To verify the integral setting make a few small (2 to 5 degree) changes in setpoint and watch the load
temperature react. Trial and error can help improve the integral setting by optimizing for experimental
needs. Faster integrals, for example, get to the setpoint more quickly at the expense of greater
overshoot. In most systems, setpoint changes that raise the temperature act differently than changes
that lower the temperature.
If it was not possible to measure the oscillation period of the load during proportional setting, start
with an integral setting of 20. If the load becomes unstable reduce the setting by half. If the load is
stable make a series of small, two to five degree, changes in the setpoint and watch the load react.
Continue to increase the integral setting until the desired response is achieved.
Divide 1000 by the period to get
2.7.4 Tuning Derivative
If an experiment requires frequent changes in setpoint or data taking between changes in the
setpoint, derivative should be considered. See Figure 2-3(e). A derivative setting of zero, off, is
recommended when the control system is seldom changed and data is taken when the load is at
steady state.
The derivative setting is entered into the Model 331 as a percentage of the integral time constant. The
setting range is 0 – 200% where 100% = ¼ I seconds. Start with a setting of 50 to 100%.
Again, do not be afraid to make some small setpoint changes; halving or doubling this setting to
watch the affect. Expect positive setpoint changes to react differently from negative setpoint changes.
2.8 AUTOTUNING
Choosing appropriate PID control settings can be tedious. Systems can take several minutes to
complete a setpoint change, making it difficult to watch the display for oscillation periods and signs of
instability. With the AutoTune feature, the Model 331 automates the tuning process by measuring
system characteristics and, along with some assumptions about typical cryogenic systems, computes
setting values for P, I, and D. AutoTune works only with one control loop at a time and does not set the
manual heater power output or heater range. Setting an inappropriate heater range is potentially
dangerous to some loads, so the Model 331 does not automate that step of the tuning process.
When the AutoTune mode is selected, the Model 331 evaluates the control loop similar to the manual
tuning section described in Paragraph 2.7. One difference is that the Model 331 does not initiate
changes to control settings or setpoint for the purpose of tuning.
control settings after the user changes the setpoint.
Unexpected or unwanted disturbances to the
It only gathers data and changes
control system can ruin experimental data being taken by the user.
Cooling System Design 2-13
Page 34
AutoTuning (Continued)
Lake Shore Model 331 Temperature Controller User’s Manual
When the user selects a new setpoint, the Model 331 logs the change in temperature at the load and
the change in heater output that was required to make the load temperature change. The old control
settings are used while data is being logged, so a good initial guess of settings can improve the
efficiency of the AutoTune feature. Once the load temperature is at or near the new setpoint, the
Model 331 looks at the logged data to calculate the best P, I, and D settings values. Those values are
then loaded and used as the control parameters so the control loop can stabilize at the new setpoint.
AutoTune does not function during a ramp because the dominant time constant of the load is disguised
by the ramp rate.
The Tune LED blinks to indicate that tuning data is being logged. The LED is illuminated but not
blinking when the tuning process is complete. The LED will not blink again until the user changes the
setpoint. If AutoTune does not give desired results the first time, make a few small (2 to 5 degree)
changes in setpoint and let the Model 331 go until the
AutoTune is able to arrive at a better set of control settings.
Tune LED stops blinking. In many cases,
There are situations where AutoTune is not the answer. The algorithm can be fooled when cooling
systems are very fast, very slow, have a large thermal lag, or have a nonlinear relationship between
heater power and load temperature. If a load can reach a new setpoint in under 10 seconds (with an
appropriate I setting >500), the cooling system is too fast for AutoTuning. Systems with a very small
thermal mass can be this fast. Adding mass is a solution, but is unappealing to users who need the
speed for fast cycle times. Manual tuning is not difficult on these systems because new settings can be
tested very quickly. Some systems are too slow for the AutoTune algorithm. Any system that takes
more than 15 minutes to stabilize at a new setpoint is too slow (with an appropriate I setting <5).
Thermal lag can be improved by using the sensor and heater installation techniques discussed above.
Lag times up to a few seconds should be expected, much larger lags can be a problem. System
nonlinearity is a problem for both AutoTune and manual tuning. It is most commonly noticed when
controlling near the maximum or minimum temperature of a temperature control system. It is not
uncommon; however, for a user to buy a cryogenic cooling system specifically to operate near its
minimum temperature. If this is the case, try to tune the system at 5 degrees above the minimum
temperature and gradually reduce the setpoint, manually adjusting the control settings with each step.
Any time the mechanical cooling action of a cryogenic refrigerator can be seen as periodic temperature
fluctuations, the mass is too small or temperature too low to AutoTune.
2.9 ZONE TUNING
Once the PID tuning parameters have been chosen for a given setpoint the whole process may have to
be done again for other setpoints significantly far away that have different tuning needs. Trying to
remember when to use which set of tuning parameters can be frustrating. The Model 331 has a Zone
feature as one of its tuning modes that can help.
To use the Zone feature the user must determine the best tuning parameters for each part of the
temperature range of interest. The parameters are then entered into the Model 331 where up to ten
zones can be defined with different P, I, D, heater range, and manual heater settings. A setpoint setting
is assigned as the maximum temperature for that zone. The minimum temperature for a zone is the
setpoint for the previous zone, 0 K is the starting point for the first zone. When Zone tuning is on, each
time the setpoint changes, appropriate control parameters are chosen automatically.
Control parameters can be determined manually or by using the AutoTune feature. AutoTune is a good
way to determine a set of tuning parameters for the control system that can then be entered as zones.
Once the parameters are chosen, AutoTune is turned off and zone tuning takes over.
Zone tuning has advantages over AutoTune during normal operation. When a new setpoint is set the
zone tuning automatically sets the appropriate control parameters for the destination. Approach to the
new setpoint is controlled with the best parameters. AutoTune, on the other hand, is not able to learn
enough about the system to change the control parameters until after the temperature gets near or to
the new setpoint. Approach to the new setpoint is controlled with the old parameters because they are
the best available.
2-14 Cooling System Design
Page 35
Lake Shore Model 331 Temperature Controller User’s Manual
CHAPTER 3
INSTALLATION
3.0 GENERAL
This chapter provides general installation instructions for the Model 331 Temperature Controller.
Inspection and unpacking instructions are provided in Paragraph 3.1. Repackaging for shipment
instructions are provided in Paragraph 3.2. An definition of rear panel controls is provided in
Paragraph 3.3. The rear panel line input assembly is described in Paragraph 3.4. Standard sensor
inputs are defined in Paragraph 3.5. Thermocouple sensor installation is described in Paragraph 3.6.
Heater output setup is provided in Paragraph 3.7. The analog output and relays of the Model 331S are
described in Paragraphs 3.8 and 3.9 respectively. An initial setup and system checkout procedure is
provided in Paragraph 3.10. For computer interface installation, refer to Chapter 6.
3.1 INSPECTION AND UNPACKING
Inspect shipping containers for external damage. All claims for damage (apparent or concealed) or
partial loss of shipment must be made in writing to Lake Shore within five (5) days from receipt of
goods. If damage or loss is apparent, please notify the shipping agent immediately.
Open the shipping containers. A packing list is included with the system to simplify checking that the
instrument, sensor(s), accessories, and manual were received. Please use the packing list and the
spaces provided to check off each item as the instrument is unpacked. Inspect for damage. Be sure to
inventory all components supplied before discarding any shipping materials. If there is damage to the
instrument in transit, be sure to file proper claims promptly with the carrier and insurance company.
Please advise Lake Shore Cryotronics of such filings. In case of parts or accessory shortages, advise
Lake Shore immediately. Lake Shore cannot be responsible for any missing parts unless notified within
60 days of shipment. The standard Lake Shore Warranty is included on the A Page (immediately
behind the title page) of this manual.
3.2 REPACKAGING FOR SHIPMENT
If it is necessary to return the Model 331, sensor(s), or accessories for recalibration, repair, or
replacement, a Return Goods Authorization (RGA) number must be obtained from a factory
representative before returning the instrument to our service department. When returning an instrument
for service, the following information must be provided before Lake Shore can attempt any repair.
1. Instrument model and serial number.
2. User’s name, company, address, and phone number.
3. Malfunction symptoms.
4. Description of system.
5. Returned Goods Authorization (RGA) number.
If possible, the original packing material should be retained for reshipment. If not available, consult Lake
Shore for shipping and packing instructions.
Installation 3-1
Page 36
Lake Shore Model 331 Temperature Controller User’s Manual
3.3 REAR PANEL DEFINITION
This paragraph provides a description of the Model 331 rear panel connections. The rear panel consists
of the line input assembly, RS-232 Connector, HEATER OUTPUT Connector, INPUT A and B Sensor
Input Connectors, the RELAY and ANALOG OUTPUT Terminal Block, and the IEEE-488 INTERFACE
Connector. Please read the entire chapter before performing the initial setup and system checkout
procedure in Paragraph 3.10. Rear panel connector pin-out details are provided in Paragraph 8.4.
CAUTION: Verify AC Line Voltage shown in the fuse holder window is appropriate for the intended
AC power input. Also remove and verify the proper fuse is installed before plugging in and
turning on the instrument.
CAUTION: Always turn off the instrument before making any rear panel connections. This is especially
critical when making sensor to instrument connections.
1 2 3
INPUT A
I+
HEATER OUTPUT
HI
60V MAX60V MAX
WARNING
NO USER SERVICEABLE PARTS
INSIDE. REFER SERVICING TO
TRAINED SERVICE PERSONNEL
I
V
!
LO
I+
V+
GND
INPUT B
I
V
!
RS-232 (DTE)
120
100/120/220/240 V
10% +6% Voltage
50-60 Hz 120 VA MAX
6
F-331-3-1.eps
100/120V
1.60 A T 250V
220/240V
0.80 A T 250V
IEEE-488 INTERFACE
SH1 AH1 T5 L4 SR1 RL1 PP0 DC1 DT0 C0 E1
5×20mm
5×20mm
RELAYS 30VDC 5A
RELAY 1 RELAY 2
NC NO
COMNC NOCOM
5
ANALOG
OUTPUT
+
V+
4
Line Input Assembly
RS-232 (DTE) 9 pin D-Style Connector
HEATER OUTPUT and Ground Banana
Jacks
Description Details
Paragraph 3.4 Figure 8-1
Paragraph 6.2.1 Figure 8-5
Paragraph 3.7 Figure 8-3
INPUT A and INPUT B Sensor (or
Thermocouple) Input Connectors
RELAYS and ANALOG OUTPUT Terminal
Block (Model 331S Only)
IEEE-488 INTERFACE Connector
(Model 331S Only)
3-2 Installation
Paragraphs 3.5
and 3.6
Paragraphs 3.8
and 3.9
Paragraph 8.4.2 Figure 8-6
Figure 3-1. Model 331 Rear Panel
Figure 8-2
Figure 8-4
Page 37
Lake Shore Model 331 Temperature Controller User’s Manual
3.4 LINE INPUT ASSEMBLY
This section describes how to properly connect the Model 331 to line power. Please follow these
instructions carefully to ensure proper operation of the instrument and the safety of operators.
Line Cord
Input
Power Switch
O = Off, l = On
Fuse
Drawer
120
F-331-3-2.eps
50-60 Hz 120 VA MAX
3.4.1 Line Voltage
The Model 331 has four different AC line voltages configurations so that it can be operated from line
power anywhere in the world. The nominal voltage and voltage range of each configuration is shown
below. (The recommended setting for 230 V operation is 240 V.)
Verify that the AC line voltage indicator in the fuse drawer window shows the appropriate AC line
voltage before turning the instrument on. The instrument may be damaged if turned on with the wrong
voltage selected. Instructions for changing the line voltage configuration are given in Paragraph 8.2.
3.4.2 Line Fuse and Fuse Holder
The line fuse is an important safety feature of the Model 331. If a fuse ever fails, it is important to
replace it with the value and type indicated on the rear panel for the line voltage setting. The letter T
on the fuse rating indicates that the instrument requires a time-delay or slow-blow fuse. Fuse values
should be verified any time line voltage configuration is changed. Instructions for changing and
verifying a line fuse are given in Paragraph 8.3.
100/120/220/240 V
10% +6% Voltage
100/120V
220/240V
1.60 A T 250V
0.80 A T 250V
5×20mm
5×20mm
Figure 3-2. Line Input Assembly
Nominal Minimum Maximum
100 V 90 V 106 V
120 V 108 V 127 V
220 V 198 V 233 V
240 V 216 V 254 V
3.4.3 Power Cord
The Model 331 includes a 3-conductor power cord that mates with the IEC 320-C14 line cord
receptacle. Line voltage is present on the two outside conductors and the center conductor is a safety
ground. The safety ground attaches to the instrument chassis and protects the user in case of a
component failure. A CE approved power cord is included with instruments shipped to Europe; a
domestic power cord is included with all other instruments (unless otherwise specified when ordered).
Always plug the power cord into a properly grounded receptacle to ensure safe instrument operation.
The delicate nature of measurement being taken with this instrument may necessitate additional
grounding including ground strapping of the instrument chassis. In these cases the operators safety
should remain the highest priority and low impedance from the instrument chassis to safety ground
should always be maintained.
Installation 3-3
Page 38
Lake Shore Model 331 Temperature Controller User’s Manual
3.4.4 Power Switch
The power switch is part of the line input assembly on the rear panel of the Model 331 and turns line
power to the instrument On and Off. When the circle is depressed, power is Off. When the line is
depressed, power is On.
3.5 DIODE/RESISTOR SENSOR INPUTS
This paragraph details how to connect diode and resistor sensors to the Model 331 inputs. Refer to
Paragraph 4.4 to configure the inputs. The optional thermocouple input is described in Paragraph 3.6.
3.5.1 Sensor Input Connector and Pinout
The input connectors are 6-pin DIN 45322 sockets. The sensor output pins are defined in Figure 3-3.
Two mating connectors (6-pin DIN plugs) are included in the connector kit shipped with the
instrument. These are common connectors, so additional mating connectors can be purchased
from local electronics suppliers. They can also be ordered from Lake Shore (P/N G-106-233).
NOTE: Pin 3 should not be used for new installations. However, to match existing Model 330
or Model 340 connector wiring, the definition of Pin 3 may be changed with a jumper.
See Figure 8-7 for jumper location.
To provide compatibility with sensor input connectors that have been wired for either Lake Shore
Model 330 or 340 Temperature Controllers, Jumper 4 (for Input A) and Jumper 7 (for Input B) are
used to select the function of Pin 3 of the connectors. The Model 330 provides a constant 1 mA
sensor excitation current on Pin 3 and 10 µA current on Pin 5. The Model 340 provides both 1 mA
and 10 µA excitation current on Pin 5 and connects Pin 3 to sensor ground reference. If the sensor
being used was wired for use with a Model 330, the jumper should be placed in the 330 position
(factory default). This provides the output current selected via the front panel input setup function on
both Pins 5 and 3. If the sensor was wired for use with a Model 340, the jumper should be placed in
the 340 position. This provides the output current on Pin 5 only and connect Pin 3 to sensor ground
reference.
I+
!
I
VV+
Pin Symbol Description
1 I– – Current
2 V– – Voltage
3
+1 mA – Model 330 Configuration
Shield – Model 340 Configuration
4 V+ + Voltage
5 I+ + Current
6 None Shield
Figure 3-3. Diode/Resistor Input Connector
3-4 Installation
Page 39
Lake Shore Model 331 Temperature Controller User’s Manual
3.5.2 Sensor Lead Cable
The sensor lead cable used outside the cooling system can be much different from what is used
inside. Between the instrument and vacuum shroud, error and noise pick up need to be minimized,
not heat leak. Larger conductor, 22 to 28 AWG stranded copper wire is recommended because it has
low resistance yet remains flexible when several wires are bundled in a cable. The arrangement of
wires in a cable is also important. For best results, voltage leads, V+ and V– should be twisted
together and current leads I+ and I– should be twisted together. The twisted pairs of voltage and
current leads should then be covered with a braided or foil shield which is connected to the shield pin
of the instrument. This type of cable is available through local electronics suppliers. Instrument
specifications are given assuming 10 feet of sensor cable. Longer cables, 100 feet or more, can be
used but environmental conditions may degrade accuracy and noise specifications. Refer to
Paragraph 2.3.6 for information about wiring inside the cryostat.
3.5.3 Grounding and Shielding Sensor Leads
The sensor inputs are isolated from earth ground to reduce the amount of earth ground referenced
noise that is present on the measurement leads. This isolation can be defeated by connecting sensor
leads to earth ground on the chassis of the instrument or in the cooling system. If one sensor lead
must be grounded, ground only one lead and ground it in only one place. Grounding leads on more
than one sensor prevents the sensor excitation current sources from operating.
Shielding the sensor lead cable is important to keep external noise from entering the measurement.
A shield is most effective when it is near the measurement potential so the Model 331 offers a shield
that stays close to the measurement. The shield of the sensor cable should be connected to the
shield pin of the input connector. It should not be terminated at the opposite end of the cable. The
shield should not be connected to earth ground on the instrument chassis or in the cooling system.
NOTE: The shell of the connector is in contact with the chassis so the cable shield
should never touch the outer shell of the connector.
3.5.4 Sensor Polarity
Lake Shore sensors are shipped with instructions that indicate which sensor leads are which. It is
important to follow these instructions for plus and minus leads (polarity) as well as voltage and current
when applicable. Diode sensors do not operate in the wrong polarity. They look like an open circuit to
the instrument. Two lead resistors can operate with any lead arrangement and the sensor instructions
may not specify. Four-lead resistors can be more dependent on lead arrangement. Follow any
specified lead assignment for four lead resistors. Mixing leads could give a reading that appears
correct but is not the most accurate.
Cathode
DT-470-SD
Diode Sensor Leads
Anode
Installation 3-5
Page 40
Lake Shore Model 331 Temperature Controller User’s Manual
3.5.5 Four-Lead Sensor Measurement
All sensors, including both two lead and four lead can be measured with a four lead technique. The
purpose of a four lead measurement is to eliminate the effect of lead resistance on the measurement.
If it is not taken out, lead resistance is a direct error when measuring a sensor.
In a four lead measurement, current leads and voltage leads are run separately up to the sensor.
With separate leads there is little current in the voltage leads so their resistance does not enter into
the measurement. Resistance in the current leads will not change the measurement as long as the
voltage compliance of the current source is not reached. When two lead sensors are used in four lead
measurements, the short leads on the sensor have an insignificant resistance.
3.5.6 Two-Lead Sensor Measurement
There are times when crowding in a cryogenic system forces users to read sensors in a two lead
configuration because there are not enough feedthroughs or room for lead wires. If this is the case,
plus voltage to plus current and minus voltage to minus current leads are attached at the back of the
instrument or at the vacuum feedthrough.
The error in a resistive measurement is the resistance of the lead wire run with current and voltage
together. If the leads contribute 2 or 3 Ω to a 10 kΩ reading, the error can probably be tolerated.
When measuring voltage for diode sensors the error in voltage can be calculated as the lead
resistance times the current, typically 10 µA. For example: a 10 Ω lead resistance times 10 µA results
in a 0.1 mV error in voltage. Given the sensitivity of a silicon diode at 4.2 K the error in temperature
would be only 3 mK. At 77 K the sensitivity of a silicon diode is lower so the error would be close to
50 mK. Again, this may not be a problem for every user.
3.5.7 Lowering Measurement Noise
Good instrument hardware setup technique is one of the least expensive ways to reduce
measurement noise. The suggestions fall into two categories: (1) Do not let noise from the outside
enter into the measurement, and (2) Let the instrument isolation and other hardware features work to
their best advantage. Here are some further suggestions:
• Use four-lead measurement whenever possible.
• Do not connect sensor leads to chassis or earth ground.
• If sensor leads must be grounded, ground leads on only one sensor.
• Use twisted shielded cable outside the cooling system.
• Attach the shield pin on the sensor connector to the cable shield.
• Do not attach the cable shield at the other end of the cable, not even to ground.
• Run different inputs and outputs in their own shielded cable.
• Use twisted wire inside the cooling system.
• Use similar technique for heater leads.
• Use a grounded receptacle for the instrument power cord.
• Consider ground strapping the instrument chassis to other instruments or computers.
Four-Lead
Diode
I+
V+
V
I
Two-Lead
Diode
Four-Lead
Platinum
I+
V+
V
I
I+
V+
V
I
3-6 Installation
Page 41
Lake Shore Model 331 Temperature Controller User’s Manual
3.6 THERMOCOUPLE SENSOR INPUTS (Model 331X-TX Only)
The information in this paragraph is for a Model 331 configured at the factory with one or two
thermocouple sensor inputs; being Model 331X-T1 or T2. Sensor connection is important when using
thermocouples because the measured signal is small. Many measurement errors can be avoided with
proper sensor installation.
CAUTION: Do not leave thermocouple inputs unconnected. Short inputs when not in use.
3.6.1 Sensor Input Terminals
Attach sensor leads to the screws on the off-white ceramic terminal blocks. Each block has two screw
terminals; one positive (on the I+
connector). See Figure 3-4.
/ V+ side of the connector), one negative (on the I– / V– side of the
The current and voltage references silkscreened on the back panel are for the diode/resistor
connectors. For thermocouples, the positive (+) wire goes to the left-side terminal and the
negative (–) wire to the right-side terminal. Remove all insulation then tighten the screws on the
thermocouple wires. Keep the ceramic terminal blocks away from heat sources including sunlight
and shield them from fans or room drafts.
Thermocouple
Positive Terminal
Common Thermocouple Polarities Positive (+) Negative (–)
Type K (Nickel-Chromium vs. Nickel-Aluminum) Chromel (YEL) Alumel (RED)
Type E (Nickel-Chromium vs. Copper-Nickel) Chromel (PUR) Constantan (RED)
Type T (Copper vs. Copper-Nickel) Copper (BLU) Constantan (RED)
Chromel-AuFe 0.03% Chromel Gold
Chromel-AuFe 0.07% Chromel Gold
Figure 3-4. Thermocouple Input Definition and Common Connector Polarities
3.6.2 Thermocouple Installation
Thermocouples are commonly used in high-temperature applications. Cryogenic use of
thermocouples offers some unique challenges. A general installation guideline is provided in
Paragraph 2.3. Consider the following when using thermocouples at low temperatures:
• Thermocouple wire is generally more thermally conductive than other sensor lead wire. Smaller
gauge wire and more heat sinking may be needed to prevent leads from heating the sample.
• Attaching lead wires and passing through vacuum tight connectors are often necessary in
cryogenic systems. Remember, the thermocouple wire
other metal, there is potential for error.
• Temperature verification and calibration of room temperature compensation is difficult after the
sensor is installed. When possible, keep a piece of scrap wire from each installation for future use.
I+
!
I
VV+
Thermocouple
Negative Terminal
is the sensor; any time it joins or contacts
3.6.3 Grounding and Shielding
For lowest measurement noise, do not ground thermocouple sensors. The instrument usually
operates with more noise if one of the thermocouples is grounded. Grounding both thermocouples is
not recommended. The instrument does not offer a shield connection on the terminal block. Twisting
the thermocouple wires helps reject noise. If shielding is necessary, extend the shield from the oven
or cryostat to cover the thermocouple wire, but do not attach the shield to the instrument.
Installation 3-7
Page 42
Lake Shore Model 331 Temperature Controller User’s Manual
3.7 HEATER OUTPUT SETUP
The following paragraphs cover the heater wiring from the vacuum shroud to the instrument for both
control loop outputs. Specifications are detailed in Paragraph 1.2. For help on choosing and installing
an appropriate resistive heater, refer to Paragraph 2.4.
3.7.1 Loop 1 Output
Of the two Model 331 control loops, Loop 1 is considered the primary loop because it is capable of
driving 50 W of heater power. The heater output for Loop 1 is a traditional control output for a
cryogenic temperature controller. It is a variable DC current source with software settable ranges and
limits. The maximum heater output current is 1 A and maximum compliance voltage is 50 V. Heater
power is applied in one of three ranges: Low, Medium, or High, as specified below.
Loop 1 Full Scale Heater Power at Typical Resistance
Heater Resistance Heater Range Heater Power
10 Ω
25 Ω
50 Ω
Low
Med
High
Low
Med
High
Low
Med
High
100 mW
1 W
10 W
250 mW
2.5 W
25 W
500 mW
5 W
50 W
3.7.2 Loop 1 Heater Output Connector
A dual banana jack on the rear panel of the instrument is
used for connecting wires to the Loop 1 heater. A standard
dual banana plug mating connector is included in the
connector kit shipped with the instrument. This is a common
jack and additional mating connectors can be purchased from
local electronic suppliers, or from Lake Shore (P/N 106-009).
The heater is connected between the HI and LO terminals.
The ground terminal is reserved for shielding the heater leads
when necessary.
3.7.3 Loop 1 Heater Output Wiring
Heater output current is what determines the size (gauge) of wire needed to connect the heater. The
maximum current that can be sourced from the Loop 1 heater output is 1 A. When less current is
needed to power a cooling system it can be limited with range settings.
When setting up a temperature control system, the lead wire for the heater be capable of carrying a
continuous current that is greater than the maximum current. Wire manufactures recommend
30 AWG or larger wire to carry 1 A of current, but there is little advantage in using wire smaller than
20 to 22 AWG outside the cryostat. Inside the cryostat, smaller gauge wire is often desirable.
It is recommended to use twisted heater leads. Large changes in heater current can induce noise in
measurement leads and twisting reduces the effect. It is also recommended to run heater leads in a
separate cable from the measurement leads to further reduce interaction.
There is a chassis ground point at the rear panel of the instrument for shielding the heater cable. The
cable shield can be tied to this point with a single banana plug. The shield should not be connected at
the opposite end of the cable and should never be tied to the heater output leads.
The Loop 1 heater output is isolated from chassis ground to reduce noise. For best noise
performance, do not connect the resistive heater or its leads to ground. Also avoid connecting heater
leads to sensor leads or any other instrument inputs or outputs.
HEATER OUTPUTHEATER OUTPUT
HIHI LOLO
60V MAX
3-8 Installation
Page 43
Lake Shore Model 331 Temperature Controller User’s Manual
3.7.4 Loop 1 Heater Output Noise
The heater output circuitry in the Model 331 must be capable of sourcing 50 W of power. This type of
circuitry can generate some electrical noise. The Model 331 was designed to generate as little noise
as possible but even noise that is a small percentage of the output voltage or current can be too
much when sensitive measurements are being made near by. If the Model 331 heater leads are too
noisy and the above wiring techniques do not help, Lake Shore offers the Model 3003 Heater Output
Conditioner that may help. Refer to Paragraph 7.4.
3.7.5 Loop 2 Output
The Model 331 has a second control loop called Loop 2. Loop 2 is an auxiliary control loop with
enough features to control a radiation shield or small sample heater. Loop 2 has a different output
from Loop 1, it uses Analog Voltage output as its actuator. It is a variable DC voltage source that can
vary from 0 V to +10 V. The output can source up to 100 mA of current providing a maximum of 1 W
of heater power.
3.7.6 Loop 2 Output Resistance
The power delivered by the Loop 2 output is calculated as: P
The output is rated for no more than 100 mA of current. For the maximum of 1 W output power use a
100 Ω resistive heater with a power rating greater than 1 W. Smaller resistance values should not be
used, but larger resistances can be used for lower power applications.
2
V
=
R
heater
3.7.7 Loop 2 Output Connector
The connector for the Loop 2 output is on the RELAYS and ANALOG OUTPUT Terminal Block. See
Pins 7 and 8 in Figure 3-5. Twisted pair of small gauge wire is recommended.
3.7.8 Loop 2 Heater Protection
The output is short protected so the instrument is not harmed if the heater resistance is too small. It is
not recommended because the additional load on instrument power supplies causes noise on internal
circuits. The second control loop has fewer features than the first including software protection and
limits. The user must be careful to build a robust system and account for the voltage range and power
up state of the control output.
3.7.9 Boosting Output Power
There are temperature control systems that require more power than the Model 331 can provide. An
auxiliary DC power supply can be used to boost the output of the Model 331. Programmable power
supplies are available that use a low current programming voltage as an input to control a high
current voltage output. Analog Voltage Output, used for Loop 2 output, provides an ideal
programming voltage for an auxiliary power supply.
The only drawback with using the analog output to program auxiliary supplies is it only has one
voltage range. The heater output for Loop 1 has several ranges that can improve resolution, but its
output is in current not voltage. To use Loop 1 to program a larger power supply, a programming
resistor can be placed across the heater output to produce a programming voltage. The programming
voltage is related to output current by:
The resistor must be chosen to convert a full scale current from the highest heater output range being
used to the full scale programming voltage of the auxiliary supply. For example, if the auxiliary supply
has a full scale programming voltage of 10 V and the maximum current for the highest heater output
range being used is 0.3 A the programming resistor should be 10 V / 0.3 A = 33 Ω. The programming
resistor must be rated for the power being dissipated in it which is:
or 3 W. The “Low” heater output range can be selected to reduce the power dissipated in the
programming resistor.
VRI
program program output
Power I R
=×
=×
2
output program
Installation 3-9
Page 44
Lake Shore Model 331 Temperature Controller User’s Manual
3.8 ANALOG OUTPUT (Model 331S Only)
The Analog Output available on the rear panel of the Model 331S is a voltage output that can be used
for monitor and control applications. Their most basic function is a temperature monitor where it puts
out a voltage that is proportional to temperature. It can be configured to monitor the output of a linear
equation which allows the user to select an offset and gain. The analog output can be controlled
manually by the user for any application that requires a programmable voltage source or as mentioned
above as Control Loop 2. Refer to Paragraph 4.16 and the ANALOG command in Chapter 6.
The analog output is a variable DC voltage source that can vary from –10 V to +10 V. The resolution of
the analog output is 0.3 mV or 0.003% of full scale. The output can source up to 100 mA of current
providing a maximum of 1 W of power. It can drive a resistive load of no less than 100 Ω. The output is
short protected so the instrument is not harmed if the heater resistance is too small. It is not
recommended because the additional load on instrument power supplies causes noise on internal
circuits.
The output for the analog outputs is available from positions 7 and 8 of the detachable RELAY and
ANALOG OUTPUT Terminal Block. See Figure 3-5. The terminal marked positive (+) is the output
voltage terminal, the terminal marked negative (–) is the ground and is attached to chassis ground
inside the instrument.
It is not recommended to attach the analog output ground to a ground outside the instrument. The
output should be read by an instrument with an isolated or differential input wherever possible.
Connecting to an external ground can cause noise in the analog output voltage or the sensor input
measurement. If this cannot be avoided, try to keep the chassis of the two instruments at the same
potential with a ground strap.
3.9 RELAYS (Model 331S Only)
The Model 331S has one high and one low relay. They are most commonly associated with the alarm
feature. The relays can also be placed in manual mode and controlled directly by the user from the front
panel or over the computer interface. Refer to Paragraph 4.15 and the RELAY command in Chapter 6.
Normally Open (N.O.), Normally Closed (N.C.), and Common (COM) contacts are available for each
relay. All contacts (including common) are isolated from the measurement and chassis grounds of the
instrument. If a relay is inactive (Off), it will be in its normal state of open or closed. When the relay is
active (On), it will be in the opposite state.
Slides into slot at
rear of Model 331
Terminal Block Connector
Lake Shore P/N 106-739
8
7
6
5
4
3
2
1
Pin Description Pin Description
Relay 2 – Common (COM)
Relay 1 – Normally Closed (NC)
1
Relay 1 – Common (COM)
2
Relay 1 – Normally Open (NO)
3
Relay 2 – Normally Closed (NC)
4
5
Relay 2 – Normally Open (NO)
6
Loop2/Analog Voltage Output – Hi (+)
7
Loop2/Analog Voltage Output – Lo (–)
8
Use screwdriver to
lock or unlock wires
Insert wire
into slot
Figure 3-5. RELAYS and ANALOG OUTPUT Terminal Block
3-10 Installation
Page 45
Relays (Continued)
Lake Shore Model 331 Temperature Controller User’s Manual
Relay connections are available in positions 1 thru 6 of the detachable RELAY and ANALOG OUTPUT
Terminal Block. See Figure 3-5. The terminal block (P/N 106-737) is included with the Model 331. For
convenient installation of wires, the terminal block may be removed from the socket. According to the
manufacturer, up to 12 AWG stranded copper wire may be used with the terminal block, though it is
unlikely that wire that large is required to carry the rated 5 amp current of the relay.
3.10 INITIAL SETUP AND SYSTEM CHE CKOUT PROCEDURE
The following is an initial instrument setup and checkout procedure. The intent is to verify basic
operation of the unit before beginning use for measurements. The procedure assumes a setup with two
Lake Shore DT-470 Silicon Diode Sensors, one control loop, a single 50 Ω heater, all readings in
Kelvin, and running in a liquid nitrogen environment.
CAUTION: Check power source for proper voltage before connecting the line cord to the
Model 331. Also check the line voltage setting on the window in the fuse
drawer. Damage to unit may occur if connected to improper voltage.
1. Check power source for proper voltage. The Model 331 operates with 100, 120, 220, or 240
(+6%, –10%) AC input voltage.
2. Check window in fuse drawer for proper voltage setting. If incorrect, refer to Paragraph 8.2.
3. Ensure the power switch is in the off (
O) position.
CAUTION: The sensor must be connected to the rear of the unit before applying power to the
Temperature Controller. Damage to the sensor may occur if connected with power on.
4. Verify your sensor installation in the liquid nitrogen environment. Then plug the control sensor
connector in INPUT A and the sample sensor connector in INPUT B. Details of sensor hardware
connections are detailed in Paragraph 3.5.
5. Connect the heater to the banana jacks labeled HEATER OUTPUT. A 50 Ω heater allows the
maximum power output of 50 W. Details of heater installation are provided in Paragraphs 2.4
and 3.7.
6. Ensure any other rear panel connections are connected before applying power to the unit. For the
Model 331E, this includes RS-232 (Paragraph 6.2.1). For the Model 331S, this includes the
IEEE-488 (Paragraph 8.4.2), Analog Output (Paragraph 3.8), and Relays (Paragraph 3.9).
7. Plug line cord into receptacle.
8. Turn the power switch to the on (l) position. The front panel will briefly display the following.
9. The typical display shown below will now appear.
The front panel display is divided into four areas. The default display settings place the Sensor A
reading in the upper left, the Sensor B reading in the upper right, the Setpoint in the lower left, and
the heater output of Loop 1 (in percent) in the lower right. All temperature readings are in Kelvin.
Each of these display areas is individually configurable by pressing the
following the instructions in Paragraph 4.3.
Installation 3-11
Lake−Shore−Model− 331
−−Temp.−Controller
À− 77.35½−Á− 77.35½
 −0.000½−−−−0%−Off
Display Format key and
Page 46
Initial Setup and System Checkout Procedure (Continued)
NOTE: For rated accuracy, the instrument should warm up for at least 30 minutes.
Lake Shore Model 331 Temperature Controller User’s Manual
10. The default input settings are “Silicon Diode” on Inputs A and B, with Input A controlling using the
“Curve 01 DT-470.” These settings can be verified by pressing the
Input Setup key and following
the instructions in Paragraph 4.4.
11. The default control mode is “Manual PID” where the Proportional, Integral, and Derivative (PID)
settings are entered by the user. The default settings are P = 50, I = 20, and D = 0. These settings
can be verified and/or adjusted by pressing the
PID/MHP key and following the instructions in
Paragraph 4.8.
12. For an experiment running at liquid nitrogen temperature, a setpoint of 77 K is good for testing
purposes. Press the
setpoint setting are discussed in Paragraph 4.11.
Setpoint key. Press the “7” key twice, then press the Enter key. Details of
À− 77.35½−Á− 75.35½
 77.000½−−−−0%−Off
13. The default setting for the heater is “Off.” To turn the heater on, press the Heater Range key. Press
s or t key until “Low” is displayed. Press the Enter key. Depending on your actual setup, you
the
may need to apply more current to the heater, which is accomplished by selecting either the “Med”
or “High” range. Details of heater settings are discussed in Paragraph 4.13.
À− 77.05½−Á− 75.10½
 77.000½−−−50%−Low
NOTE: If any problems appear, immediately press the Heater Off key. If any error messages are
displayed, refer to Paragraph 8.8 for details.
The Model 331 should now be controlling the temperature in the experimental setup at the setpoint
temperature. Once this initial checkout procedure is successfully completed, the unit is ready for normal
operation. We recommend all users thoroughly read Chapter 4 – Operation before attempting to use
the Model 331 in an actual experiment or application.
3-12 Installation
Page 47
Lake Shore Model 331 Temperature Controller User’s Manual
CHAPTER 4
OPERATION
4.0 GENERAL
This chapter describes Model 331 Temperature Controller operation. A definition of front panel controls
is provided in Paragraph 4.1. Turning power on is described in Paragraph 4.2. Paragraphs 4.3 thru 4.20
describe operation of instrument features. Instrument default settings are provided in Paragraph 4.21.
Advanced operation is described in Chapter 5. Computer interface operation is detailed in Chapter 6.
4.1 FRONT PANEL DESCRIPTION
This paragraph provides a description of the front panel controls and indicators for the Model 331.
4.1.1 Keypad Definitions
An abbreviated description of each key is provided as follows. A more detailed description of each
function is provided in subsequent paragraphs. See Figure 4-1.
AutoTune Allows selection of closed loop tuning mode: AutoTune PID, PI, P, Manual PID, or
Loop Toggles the front panel display and key functions between Loop 1 and 2. Operates
Heater Range For Loop 1, allows selection of High (50 W), Medium (5 W), or Low (0.5 W) heater
Heater Off Turns the heater off for Loop 1 or turns the control output off for Loop 2. Refer to
Zone for the currently selected loop. Refer to Paragraph 4.9.
with: Control Setup, Setpoint, PID/MHP, Zone Settings, AutoTune, Heater Range,
and Heater Off. Refer to Paragraph 4.6.1.
range. For Loop 2, allows selection of Heater On/Off. Refer to Paragraph 4.13.
Paragraph 4.13.
LakeShore
Control
Setup
Zone
Setting
1 234 5+/
Setpoint
PID/
MHP
6 7 89 0
C331-1-1.eps
Operation 4-1
331 Temperature Controller
Input
Setup
Curve
Entry
Display
Format
Math
Alarm
Analog
Output
Remote/
Local
Interface
Figure 4-1. Model 331 Front Panel
Escape
Enter
Control A
Control B
Auto
Tune
Loop
Tune
Ramp
Heater
Range
Heater
Off
Remote
Alarm
Page 48
Lake Shore Model 331 Temperature Controller User’s Manual
Keypad Definitions (Continued)
Control Setup Allows selection of control input, setpoint units, closed or open loop control mode,
power up enable, display of heater output units, setpoint ramp enable, and ramp
rate for the currently selected loop. Refer to Paragraph 4.7 for control setup and
Paragraph 4.12 for ramp feature.
Setpoint Allows entry of control setpoint for the currently selected loop. Refer to Paragraph
4.11. A discussion of the ramp feature is provided in Paragraph 4.12.
Zone Settings Allows entry of up to 10 temperature control zones of customer-entered PID
settings and Heater Ranges for the currently selected loop. Refer to Paragraph
4.10.
PID/MHP Allows manual adjustment of control parameters Proportional, Integral, and
Derivative, or Manual Heater Power (MHP) output for the currently selected loop.
Refer to Paragraph 4.8.
Input Setup Allows selection of sensor input type and curve. Refer to Paragraph 4.4 for sensor
input setup and Paragraph 4.5 for curve selection.
Curve Entry Allows entry of up to twenty 200-point CalCurves or user curves and SoftCal.
Refer to Chapter 5 – Advanced Operation, Paragraph 5.2 Front Panel Curve
Entry Operations.
Display Format Allows the user to configure the display and select the units or other source of the
readings. Refer to Paragraphs 4.1.4 and 4.3. Press and hold to set display
brightness. Refer to Paragraph 4.18.
Math Allows the user to configure the math features: Max/Min, linear equation, and filter.
Press twice to reset the stored Max/Min readings. Refer to Paragraph 4.14.
Alarm Allows the user to configure both the alarms and relays (331S Only). Refer to
Paragraph 4.15.
Analog Output Allows the user to configure the analog output feature. Also used to assign the
analog output to Loop 2 control output thus enabling Loop 2 (331S Only). Refer to
Paragraph 4.16.
Remote/Local Sets remote or local operation: Remote refers to operation is via IEEE-488
Interface (Model 331S only); Local refers to operation via the front panel. Refer to
Paragraph 4.19.
Interface Sets the Baud rate of the serial interface and IEEE-488 address and terminators
(331S Only). Refer to Paragraph 4.20.
s Serves two functions: chooses between parameters during setting operations and
to increment a numerical parameter values.
t Serves two functions: chooses between parameters during setting operations and
decrements numerical parameter values.
Escape Terminates a setting function without changing the existing parameter value. Press
and hold to reset instrument to default values. Refer to Paragraph 4.21.
Enter Completes setting functions and returns to normal operation. Press and hold to
lock or unlock keypad. Refer to Paragraph 4.17.
0 – 9, +/–, . Used for entry of numeric data. Includes a key to toggle plus (+) or minus (–), and a
key for entry of a decimal point. Refer to Paragraph 4.1.3.
4-2 Operation
Page 49
4.1.2 Annunciators
LED Annunciators
Six blue LED annunciators are included to provide visual feedback of the following operation.
Control A On when Input A is being used as the control input for the loop being displayed. Refer
to Paragraph 4.4.
Control B On when Input B is being used as the control input for the loop being displayed. Refer
to Paragraph 4.4.
Tune On steady when the AutoTune feature is on, blinking when AutoTune is actively
gathering data. Refer to Paragraph 4.9.
Ramp On steady when the Ramp feature is on, blinking during a setpoint ramp. Refer to
Paragraph 4.12 for turning ramping on and setting the ramp rate.
Remote On when the instrument is in Remote mode, i.e., may be controlled via the IEEE-488
Interface. Refer to Paragraphs 4.19 and 4.20.
Alarm On steady when the alarm feature is on, blinking when any alarm is active. Refer to
Display Annunciators
Paragraph 4.15.
A Sensor Input A Ω Sensor Units of Ohms
B Sensor Input B mV Sensor Units of Millivolts
S Setpoint > Maximum Reading Value
K Temperature in Kelvin < Minimum Reading Value
C Temperature in Celsius / Result of Linear Equation
V Sensor Units of Volts
Lake Shore Model 331 Temperature Controller User’s Manual
4.1.3 General Keypad Operation
There are three basic keypad operations: Direct Operation, Setting Selection, and Data Entry.
Direct Operation. The key function occurs as soon as the key is pressed, e.g., Loop, Heater Off, and
Remote/Local.
Setting Selection. Allows the user to select from a list of values. During a selection sequence the
s or t key are used to select a parameter value. After a selection is made the Enter key is pressed
to make the change and advance to the next setting, or the
normal display without changing the present setting. The instrument retains any values entered prior
to pressing the
Escape key. Some selections are made immediately after pressing a function key;
like Heater Range. Most are part of a string of settings. Setting selections always include the
“Select for ...
st” display, a sample of which is shown below.
Select for Disp 1 °®
Display Input A
Data Entry. Allows the user to enter number data using the data entry keys. Data entry keys include
the numbers 0
parameter that requires data entry. During a data entry sequence use the data entry keys to enter the
number value, press the
Escape key once to clear the entry, twice to return to the normal display. Most data entry operations
are combined with other settings and grouped under a function key. Temperature or sensor unit
parameters have the same setting resolution as the display resolution for their corresponding
readings. Data entry always includes the “Enter for ...” display, a sample of which is shown below.
– 9, +/–, and decimal point. Proportional control parameter is an example of a
Enter key to accept the new data and advance to the next setting. Press the
Escape key is pressed to return to the
Operation 4-3
Enter for Loop 1
Prop (P) 50.000
Page 50
Lake Shore Model 331 Temperature Controller User’s Manual
4.1.4 Display Definition
In normal operation, the 2 row by 20 character vacuum fluorescent display is divided into four userconfigurable areas that can provide temperature readings, setpoint display, and heater status. Other
information is displayed when using the various functions on the keypad. See Figure 4-2.
Display Location 1:
Input A
Input B
None = No Display
À 295.22½ Á 295.22½
 295.00½ 0% Off
Source:
K = Kelvin
C = Celsius
Sensor (V, mV, or Ω)
Linear (/)
Min (<)
Max (>)
Display Location 2:
Input A
Input B
None = No Display
Input Reading Source
Source
(Same choices as
Display Location 1)
Display Location 3:
Input A
Input B
Setpoint
*
None = No Display
Setpoint Units and Heater Out Current or Power settings are
*
under the Control Setup key. All remaining selections in this
illustration are made under the Display Format key.
C331-4-2.eps
Source:
(Same choices as
Display Location 1)
Units:
K = Kelvin
C = Celsius
Sensor (V, mV, or Ω)
Display Location 4: Source:
Input A
Input B
Heater Out
*
None = No Display
(Same choices as
Display Location 1)
Heater Output (Loop 1):
0% Off = Heater Off
XX% Low = 0.5 W Heater Range
XX% Med = 5 W Heater Range
XX% High = 50 W Heater Range
-or-
Heater Output (Loop 2):
Off L2 = Heater Off
XX% L2 = Heater On (1 W)
Figure 4-2. Display Definition
4.2 TURNING POWER ON
After verifying line voltage (Paragraph 3.4), plug the instrument end of the line cord (included with the
connector kit) into the power and fuse assembly receptacle on the instrument rear. Plug the opposite
end of the line cord into a properly grounded, three-prong receptacle. Place the power switch, located
next to the line cord receptacle, to the On (
l) position. The instrument initiates the following power up
sequence: the instrument alarm sounds once; the display shows the following startup message.
Lake Shore Model 331
Temp. Controller
The normal reading display appears. If the instrument does not complete the sequence or if a general
error message displays, there may be a problem with the line power or the instrument. Individual
messages in a reading location normally indicate that input setup is required.
4-4 Operation
Page 51
Lake Shore Model 331 Temperature Controller User’s Manual
4.3 DISPLAY FORMAT AND SOURCE (UNITS) SELECTION
In the normal display, the display is divided into four user-configurable areas that can provide
temperature readings, setpoint display, and heater status. Figure 4-3 illustrates the display location
numbering and available selections for each location. To change Setpoint units and select Heater Out
Power or Current, refer to the description of
Control Setup in Paragraph 4.7. To change display
brightness, refer to Paragraph 4.18.
Display Location 1:
Input A
Input B
None
Display Location 2:
Input A
Input B
None
À 295.22½ Á 295.22½À 295.22½ Á 295.22½
 295.00½  295.00½ 0% Off 0% Off
Display Location 3:
Input A
Input B
Setpoint
C-331-4-3.eps
None
Display Location 4:
Input A
Input B
Heater Out
None
Figure 4-3. Display Format Definition
To configure a display location, press the Display Format key to display the following screen.
Select With °®
Display Location 1
Use the s or t key to increment or decrement through Display Locations 1 thru 4. For this example,
select Display Location 1, then press the
Enter key. You will see the following display
Select for Disp 1 °®
Display Input A
Use the s or t key to cycle between Input A, Input B, or None. For this example, select Input A then
press the
Enter key. You will see the following display
Use the s or t key to cycle through the following data sources: Temp K, Temp C, Sensor, Linear, Min,
and Max. For this example, select Temp K then press the
NOTE: The sensor reading of the instrument can always be displayed in sensor units.
If a temperature response curve is selected for an input, its readings may also
be displayed in temperature.
Operation 4-5
Select for Disp 1 °®
Source Temp K
Enter key.
Page 52
Display Format (Continued)
Lake Shore Model 331 Temperature Controller User’s Manual
With the settings from the previous example, Display Location 1 will resemble the following.
À 295.22½
The process is the same for the other three display locations. However, additional choices are provided
for Display Location 3 and 4, being Setpoint and Heater Out respectively.
In the following example, we will setup Display Location 3 to show the setpoint. Press the Display
Format
key.
Select With °®
Display Location 3
Use the s or t key to increment or decrement through Display Locations 1 thru 4. For this example,
select Display Location 3, then press the
Enter key. You will see the following display
Select for Disp 3 °®
Display Setpoint
Use the s or t key to cycle between Input A, Input B, Setpoint, or None. For this example, select
Setpoint then press the
With the settings from the previous example, and assuming you setup Display Location 1 detailed
above, the display will resemble the following.
Enter key.
À 295.22½ Á 295.22½
 0.000½
To change the setpoint units, refer to Control Setup, Paragraph 4.7.
4-6 Operation
Page 53
Lake Shore Model 331 Temperature Controller User’s Manual
4.4 INPUT SETUP
The Model 331 supports a variety of temperature sensors sold by Lake Shore and other manufacturers.
An appropriate sensor type must be selected for each of the two inputs. If the exact sensor model is not
shown, use the sensor input performance chart in Table 4-1 to choose an input type with similar range
and excitation. For additional details on sensors, refer to the Lake Shore Temperature Measurement
and Control Catalog or visit our website at www.lakeshore.com.
Table 4-1. Sensor Input Types
Display Message
Input
Range
Excitation Sensor Type
Curve
Format
Coefficient
Lake Shore Sensors
*
Silicon Diode 2.5 V 10 µA Silicon Diode V/K Negative DT-4XX, DT-500, DT-670 Series
GaAlAs Diode
7.5 V 10 µA
Gallium-AluminumArsenide Diode
V/K Negative TG-120 Series
2.5V, 1mA 2.5 V 1 mA Diode V/K Negative —
7.5V, 1mA
100Ω Plat/250
100Ω Plat/500 500 Ω
1000Ω Plat
NTC RTD
7.5 V 1 mA Diode
250
5000
7500
Ω
Ω
Ω
1 mA
1 mA
1 mA
10 µA
100
Rhodium-Iron RTD
100 Ω Plat. RTD >675K
1000 Ω Plat. RTD
Negative Temperature
Coefficient (NTC) RTD
Ω Plat. RTD <675K;
Thermo/25mV ±25 mV NA Thermocouple
Thermo/50mV
±50 mV NA Thermocouple
V/K Negative
Ω/K
Ω/K
Positive
Positive
log R/K Negative
mV/K Positive
—
PT-100 Series Platinum,
RF-800 Rhodium-Iron
—
Cernox™, High-Temperature
Cernox™, Carbon Glass™,
Germanium, Rox™, and Thermox
Chromel-AuFe (0.07%),
Type E (Chromel-Constantan),
Type K (Chromel-Alumel),
Type T (Copper-Constantan),
* Refer to the Lake Shore Temperature Measurement and Control Catalog for complete details on all
Lake Shore Temperature Sensors.
4.4.1 Diode Sensor Input Setup – 10 µA Excitation Current
Diode sensors include the Silicon and Gallium-Aluminum-Arsenide (GaAlAs) detailed in Table 4-1.
More detailed specifications are provided in Table 1-3. Input ranges for are fixed to 0
diodes and 0
To setup a diode sensor input, press the Input Setup key. The first screen appear as follows.
– 7.5 V for GaAlAs diodes. Both use a sensor excitation current of 10 µA.
– 2.5 V for silicon
Select With °®
Input Setup Input A
Use the s or t key to toggle between Input A and B. Press the Enter key.
Select for InputA °®
Type Silicon Diode
Use the s or t key to cycle through the sensor types shown in Table 4-1, with “Silicon Diode” and
“GaAlAs Diode” being the relevant choices. Press the
select a temperature curve or press the
Operation 4-7
Escape key to return to the normal display.
Enter key. Proceed to Paragraph 4.5.1 to
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Lake Shore Model 331 Temperature Controller User’s Manual
4.4.2 Diode Sensor Input Setup – 1 mA Excitation Current
As an alternative to the standard diode input configuration listed above, the user may select 1 mA
excitation while the input configuration matches the diode input setup as detailed in Table 4-1. Input
ranges are fixed to 0
– 2.5 V and 0 – 7.5 V.
To access the alternative setup, the diode current must be set to 1 mA. Press and hold the Input
key for 10 seconds to display the screen shown as follows:
Setup
Select for InputA °®
Diode Current 1mA
Use the s or t key to toggle between 10 µA and 1 mA to select the diode current for Input A. 1 mA
must be selected for the special sensor input to be available for Input A. Press the
Enter key.
Select for InputB °®
Diode Current 1mA
Use the s or t key to toggle between 10 µA and 1 mA to select the diode current for Input B. 1 mA
must be selected for the special sensor input to be available for Input B. Press the
To setup the diode input using 1 mA excitation, press the Input Setup key. The first screen appears
as follows.
Enter key.
Select With °®
Input Setup Input A
Use the s or t key to toggle between Input A and B. Press the Enter key.
Select for InputA °®
Type 2.5V, 1mA
Use the s or t key to cycle through the sensor types shown in Table 4-1, with “2.5V, 1mA” and
“7.5V, 1mA” being the relevant choices. Press the
temperature curve or press the
4-8 Operation
Enter key. Proceed to Paragraph 4.5.1 to select a
Escape key to return to the normal display.
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Lake Shore Model 331 Temperature Controller User’s Manual
4.4.3 Resistor Sensor Input Setup
Resistor sensors include the Platinum, Rhodium-Iron, and various NTC RTD sensors (e.g., Cernox™,
Rox™, Thermox) detailed in Table 4-1. More detailed specifications are provided in Table 1-3. Input
range is fixed to type of sensor. The excitation current applied by the Model 331 is determined by the
user selection of Negative Temperature Coefficient (NTC) = 10 µA or Positive Temperature
Coefficient (PTC) = 1 mA.
To setup a resistor sensor input, press the Input Setup key. The first screen appear as follows.
Select With °®
Input Setup Input A
Use the s or t key to toggle between Input A and B. Press the Enter key.
Select for InputA °®
Type NTC RTD
Use the s or t key to cycle through the sensor types shown in Table 4-1, with “100Ω Plat/250,”
“100Ω Plat/500,” “1000Ω Plat,” and “NTC RTD” being the relevant choices. Press the
4.4.3.1 Thermal EMF Compensation
To keep power low and avoid sensor self heating, the sensor excitation is kept low. There are two
major problems that occur when measuring the resulting small DC voltages. The first is external
noise entering the measurement through the sensor leads which is discussed with sensor setup.
The second problem is the presence of thermal EMF voltages, sometimes called thermocouple
voltages, in the lead wiring. Thermal EMF voltages appear whenever there is a temperature
gradient across a piece of voltage lead. Thermal EMF voltages must exist because the sensor is
almost never the same temperature as the instrument. They can be minimized by careful wiring,
making sure the voltage leads are symmetrical in the type of metal used and how they are joined,
and by keeping unnecessary heat sources away from the leads. Even in a well designed system
thermal EMF voltages can be an appreciable part of a low voltage sensor measurement.
The Model 331 can help with a thermal correction algorithm. The instrument will automatically
reverse the polarity of the current source every other reading. The average of the positive and
negative sensor readings will cancel the thermal EMF voltage which is present in the same polarity,
regardless of current direction.
To turn reversal on or off press the Input Setup key and press the Enter key until the following
display appears.
Enter key.
Resistor sensors have the additional choice of turning current reversal On or Off, with the default
being Off. If turned On, the Model 331 will automatically reverse the polarity. Press the
Proceed to Paragraph 4.5.2 to select a temperature curve or press the
normal display.
Operation 4-9
Select for InputA °®
Reversal Off
Enter key.
Escape key to return to the
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Lake Shore Model 331 Temperature Controller User’s Manual
4.4.4 Thermocouple Sensor Input Setup (Model 331X-TX only)
The following thermocouple screens are only displayed when the Model 331 hardware is configured
at the factory with one or two thermocouple sensor inputs; being Model 331X-T1 or T2.
The user has the choice of two different input voltage ranges: ±25 mV and ±50 mV. The ±25 mV
range is recommended for cryogenic applications or higher temperatures less than 500 K. Since
thermocouple voltage can exceed 25 mV on some thermocouple types, the ±50 mV range is
recommended for temperatures above 500 K.
The voltage range for Inputs A and B is set independently. To setup a thermocouple sensor input,
press the
Input Setup key. The first screen appear as follows.
Select With °®
Input Setup Input A
Use the s or t key to toggle between Input A and B. Press the Enter key.
Select for InputA °®
Type Thermo/25mV
Use the s or t key to cycle through the sensor types shown in Table 4-1, with “Thermo/25mV” and
“Thermo/50mV” being the relevant choices. Press the
select a room-temperature compensation or press the
4.4.4.1 Room-Temperature Compensation
Room-temperature compensation is required to give accurate temperature measurements with
thermocouple sensors. It corrects for the temperature difference between the instrument thermal
block and the curve normalization temperature of 0 °C. An external ice bath is the most accurate
form of compensation, but is often inconvenient. The Model 331 has built-in room-temperature
compensation that is adequate for most applications. The built-in compensation can be turned on or
off by the user. It operates with any thermocouple type that has an appropriate temperature
response curve loaded. Room-temperature compensation is not meaningful for sensor units
measurements.
NOTE: Room temperature compensation should be calibrated as part of every installation.
To turn room temperature compensation on or off, press the Input Setup and press Enter until the
following display appears.
Enter key. Proceed to Paragraph 4.4.3.1 to
Escape key to return to the normal display.
Select for InputA °®
Room Comp On
Use the s or t key to turn room-temperature compensation on or off, then press the Enter key.
The default setting is On. If curve is set to “None” the room-temperature compensation selection is
automatically turned off.
4-10 Operation
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Lake Shore Model 331 Temperature Controller User’s Manual
4.4.4.2 Room-Temperature Calibration Procedure
Room-temperature calibration is used to calibrate the built-in compensation and is recommended
when a thermocouple is first installed or any time a thermocouple is changed.
Factory calibration of the instrument is accurate to within approximately ±1 K. Differences in
thermocouple wire and installation technique create errors greater than the instrument errors.
Therefore, the best accuracy is achieved by calibrating with the thermocouple actually being used
because it eliminates all sources of error. If that is not possible, use a thermocouple made from the
same wire. For less demanding applications, a short across the input terminals will suffice. If the
Model 331 is configured as dual thermocouple unit, calibrate both inputs even if they use the same
type of thermocouple. An appropriate curve must be selected and room temperature compensation
must be turned on before calibration can be started.
There are three options for room temperature calibration:
Cleared. The previous room-temperature calibration value is cleared and no adjustment will be
made to the temperature value provided by the internal temperature sensor when
compensation is on.
No. Use the room-temperature calibration value determined the last time the room-temperature
calibration procedure was performed.
Yes. Perform the room-temperature calibration procedure that follows.
Calibration Procedure
1. Attach a thermocouple sensor or direct short across the input terminals of the thermocouple
input. See Figure 3-4 for polarity.
2. Place the instrument away from drafts. If calibrating using a short, place an accurate roomtemperature thermometer near the terminal block.
3. Allow the instrument to warm up for at least ½ hour without moving or handling the sensor.
4. If calibrating with a short skip to step 6, otherwise insert the thermocouple into the ice-bath,
liquid nitrogen, helium dewar, or other know fixed temperature. The temperature should be
close to the measurement temperature that requires best accuracy.
5. Read the displayed temperature. If the temperature display is not as expected, check to be
sure that the thermocouple is making good thermal contact. If possible, add a thermal mass to
the end of the thermocouple.
6. Press the
the
Input Setup key and press the Enter key until the “Room Cal” screen appears. Press
s or t key until the “Yes” selection appears then press the Enter key.
7. The current temperature reading is displayed in Kelvin.
Enter the true temperature that the thermocouple should read. If input is shorted, then enter the
actual room temperature measured by the thermometer. Press the
8. To verify calibration, check that the temperature reading for the calibrated input matches the
room-temperature calibration setting value.
Operation 4-11
Select for InputA °®
Room Cal Yes
Select for InputA
Temp 294.15½
Enter key to save the value.
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Lake Shore Model 331 Temperature Controller User’s Manual
4.5 CURVE SELECTION
The Model 331 supports a variety of temperature sensors sold by Lake Shore and other manufacturers.
After the appropriate sensor type is selected for each of the two inputs (Paragraph 4.4), an appropriate
curve may be selected for each input. The Model 331 can use curves from several sources. Standard
curves are included with every instrument and numbered 1
– 20. User curves, numbered 21 – 41, are
loaded when a sensor does not match a standard curve. CalCurve options are stored as user curves.
SoftCal calibrations are stored as user curves or user can enter their own curves from the front panel
(Paragraph 5.2) or computer interface (Chapter 6). The complete list of sensor curves built in to the
Model 331 is provided in Table 4-2.
During normal operation, only the curves related to the input type you have selected are displayed. If
the curve you wish to select does not appear in the selection sequence make sure the curve format
matches the recommended format for the input type selected. Refer to Table 4-1.
NOTE: The sensor reading of the instrument can always be displayed in sensor units.
If a temperature response curve is selected for an input, its readings may also
be displayed in temperature.
Table 4-2. Sensor Curves
Curve
Number
Display
Sensor
Type
Model
Number
Temperature
Range
For Data Points,
Refer To:
01 DT-470 Silicon Diode DT-470 1.4 – 475 K Table D-1
02 DT-670 Silicon Diode DT-670 1.4 – 500 K Table D-2
03 DT-500-D * Silicon Diode DT-500-D 1.4 – 365 K Table D-3
04 DT-500-E1 * Silicon Diode DT-500-E1 1.1 – 330 K Table D-3
05 Reserved – – – –
06 PT-100
07 PT-1000 *
100Ω Plat/250
100Ω Plat/500
1000Ω Plat
PT-100 30 – 800 K Table D-4
PT-1000 30 – 800 K Table D-4
08 RX-102A-AA NTC RTD Rox RX-102A 0.05 – 40 K Table D-5
09 RX-202A-AA NTC RTD Rox RX-202A 0.05 – 40 K Table D-6
10 Reserved – – – –
11 Reserved – – – –
12 Type K Thermo/25mV & 50mV Type K 3 – 1645 K Table D-7
13 Type E Thermo/25mV & 50mV Type E 3 – 1274 K Table D-8
14 Type T Thermo/25mV & 50mV Type T 3 – 670 K Table D-9
15
AuFe 0.03%
*
Thermo/25mV & 50mV
AuFe 0.03% *
– 500 K Table D-10
3.5
16 AuFe 0.07% Thermo/25mV & 50mV AuFe 0.07% 3.15 – 610 K Table D-11
17 Reserved – – – –
18 Reserved – – – –
19 Reserved – – – –
20 Reserved – – – –
21 – 41 User Curves – – – –
* No longer sold by Lake Shore.
4-12 Operation
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Lake Shore Model 331 Temperature Controller User’s Manual
4.5.1 Diode Sensor Curve Selection
Once the input is setup for the Silicon or Gallium-Aluminum-Arsenide Diode (Paragraph 4.4.1), you
may choose a temperature curve. Standard curve numbers 1 thru 4, or none, being relevant choices.
You are also given the choice of “None.” You may also choose from any appropriate User Curves
stored in Curve Numbers 21 thru 41. Data points for standard diode curves are detailed in Tables D-1
thru D-3 in Appendix D.
Press the Input Setup key. Press the Enter key until you see the curve selection screen shown
below.
Select for InputA °®
Curve 01 DT-470
Use the s or t key to cycle through the sensor curves until the desired curve is displayed. Press the
Enter key to return to the normal display.
NOTE: Standard diode curves and typical sensor performance (Table 1-3) are calculated
using 10 µA excitation. Sensor temperature response characteristics will be altered
if 1 mA excitation is selected.
4.5.2 Resistor Sensor Curve Selection
Once the input is setup for the Platinum, Rhodium-Iron, or various NTC RTD sensors (Paragraph
4.4.2), you may choose a temperature curve. Standard curve numbers 6 and 7 being relevant to
Platinum, or curves 8 and 9 being relevant to Rox™ sensors. You are also given the choice of
“None.” You may also choose from any appropriate User Curves stored in Curve Numbers 21 thru 41.
Data points for resistor curves are detailed in Tables D-4 thru D-6 in Appendix D.
Press the Input Setup key. Press the Enter key until you see the curve selection screen shown
below.
Select for InputA °®
Curve 08 RX-102A-AA
Use the s or t key to cycle through the sensor curves until the desired curve is displayed Press the
Enter key to return to the normal display.
4.5.3 Thermocouple Sensor Curve Selection
The following thermocouple screens are only displayed when the Model 331 hardware is configured
at the factory with one or two thermocouple sensor inputs; being Model 331X-T1 or -T2.
Once the input is setup for the thermocouple input voltage (Paragraph 4.4.3), you may choose a
temperature curve. Press the
You are also given the choice of “None.” You may also choose from any appropriate User Curves
stored in Curve Numbers 21 thru 41. Data points for thermocouple curves are detailed in Tables D-7
thru D-11 in Appendix D. Press the
Use the s or t key to cycle through the sensor curves until the desired curve is displayed. Press the
Enter key to return to the normal display.
Operation 4-13
Input Setup key. Standard curve numbers 12 thru 16 being relevant.
Enter key until you see the curve selection screen shown below.
Select for InputA °®
Curve 16 AuFe 0.07%
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Lake Shore Model 331 Temperature Controller User’s Manual
4.6 TEMPERATURE CONTROL
There are many steps involved in setting up a temperature control loop. Chapter 2 of this manual
describes the principals of closed loop (feedback) control. Chapter 3 describes necessary hardware
installation. The following sections of this chapter describe how to operate the control features and set
control parameters. Each control parameter should be considered before enabling a control loop or the
instrument may not be able to perform the most simple control functions. A good starting point is
deciding which control loop to use, whether to operate in open or closed control mode and which tuning
mode is best for the application. Other parameters fall into place once these have been chosen.
4.6.1 Control Loops
The Model 331 is capable of running either one (331E) or two simultaneous (331S) control loops.
Their capabilities are compared in Table 4-3. As shown there the primary difference between the two
loops is their control output.
Loop 1: Loop 1, the primary control loop, is the traditional control loop for a cryogenic temperature
controller. It includes the largest set of hardware and software features making it very flexible and
easy to use. Loop 1 uses the heater output as its control output giving it several advantages. The
heater output is a well regulated 50 W DC output with three power ranges. This provides quiet, stable
control for a broad range of temperature control systems in a fully integrated package.
Loop 2: Loop 2, the auxiliary control loop (331S only), shares most of the operational features of loop
1 but uses the 1 W analog voltage output as its control output. By itself, loop 2 is capable of driving a
sample heater or other low power load. It is also well suited to drive the programming input of a
voltage programmable power supply. In combination the controller and supply can be used to control
large loads at high temperatures, or can be used in bipolar mode to control thermoelectric devices.
The keypad and display operate on one loop at a time. To toggle display and keypad operation
between loop 1 and loop 2 press the
Loop key to toggle the display and keypad operation between
Loop 1 and 2. A brief display message indicates which control loop has been selected. You can
determine which loop is active by looking at the heater output display. Loop 1 has “Low,” “Med,” or
“High” in the heater display. Loop 2 has “L2” in the heater display. Also, when you select any of the
following parameters, the active loop number will be displayed: Control Setup, Setpoint, PID/MHP,
Zone Settings, AutoTune, and Heater Range.
Table 4-3. Comparison of Control Loops 1 and 2
Feature Loop 1
Control Output Heater Output Analog Output
Maximum Output Power 50 W 1 W
Output Type Current Source Voltage Source
Multiple Output Ranges Yes No
Closed Loop PID Control Yes Yes
AutoTune Yes Yes
Zone Tuning Yes Yes
Ramping Yes Yes
Open Loop Control Yes Yes
Display in Current or Power Yes No
Front Panel Display Yes Yes
Setpoint Limit Yes Yes
Heater Fault Detection Yes No
Bipolar Operation No Yes
4-14 Operation
Loop 2
(Model 331S Only)
Page 61
4.6.2 Control Modes
The Model 331 offers two control modes, closed loop and open loop. To select a control mode refer
to Paragraph 4.7.
Closed Loop Control: Closed loop control, often called feedback control, is the control mode most
often associated with temperature controllers. In this mode the controller attempts to keep the load at
exactly the user entered setpoint temperature. To do this, it uses feedback from the control sensor to
calculate and actively adjust the control output or heater setting. The Model 331 uses a control
algorithm called PID that refers to the three terms used to tune the controller for each unique system.
Manual heater power output can also be used during closed loop control. Closed loop control is
available for both control loops and offers several methods of tuning.
Open Loop Control: Open loop control is less complicated than closed loop control but is also less
powerful. Open loop control mode allows the user to directly set the manual heater power output for
Loop 1, control output for Loop 2, using only the Manual Heater Power (MHP) output parameter.
During Open Loop control only the heater range and MHP Output parameters are active, the setpoint,
control sensor and PID parameters are ignored. This type of control guarantees constant power to the
load but it does not actively control temperature. Any change in the characteristics of the load will
cause a change in temperature. Closed loop control is available for both loops and no tuning is
required.
4.6.3 Tuning Modes
The Model 331 offers three tuning modes or ways to set the necessary P, I and D parameters for
closed loop control. MHP output is active during closed loop control and must be set to zero if not
wanted. Heater range must also be considered as part of tuning when using control Loop 1.
Manual PID Tuning: Manual tuning is the most basic tuning method. The user manually enters
parameter values for P, I and D as well as heater range using their knowledge of the cooling system
and some trial and error. Refer to Paragraphs 2.7 and 4.8 for guidelines. Manual tuning can be used
in any situation within the control capabilities of the instrument.
AutoTune: The Model 331 automates the tuning process with an AutoTune algorithm. This algorithm
measures system characteristics after a setpoint change and calculates P, I and D. The user must set
heater range. AutoTune will not work in every situation. Refer to Paragraphs 2.8 and 4.9 for details.
Zone Tuning: Optimal control parameters values are often different at different temperatures within a
system. Once values have been chosen for each temperature range or zone, the zone feature can
automatically select the correct set each time the setpoint is changed. This mode does not help
choose control parameter values; it helps use the values more efficiently. Refer to Paragraphs 2.9
and 4.10 for details.
Lake Shore Model 331 Temperature Controller User’s Manual
4.7 CONTROL SETUP
After the Input Setup has been completed (Paragraph 4.4) and Loop is selected (Paragraph 4.6.1), the
user can begin to setup temperature control parameters.
Control input is the sensor input that is used for control feedback in closed loop control. Either Input A
or B can be assigned to either Loop 1 or 2. It is not recommended to assign both loops to one input.
Control input is ignored when using open loop control mode. To change control input, press the
key and the following screen will appear.
Setup
Use the s or t key to toggle between Input A or B. Press the Enter key to accept the setting and
continue with additional selections. You can press the
Operation 4-15
Select for Loop 1 °®
Control with Input A
Escape key anytime to exit the routine.
Control
Page 62
Control Setup (Continued)
Lake Shore Model 331 Temperature Controller User’s Manual
The control setpoint can be displayed and set in temperature or sensor units. Changing setpoint units
does not change operation of the controller, only the way the setpoint is displayed and entered. A valid
curve must be assigned to the control input to use temperature units. To change setpoint units press
Control Setup key and press Enter until the following display appears.
the
Select for Loop 1 °®
SP Units Temp K
Use the s or t key to cycle through the following setpoint units: Temp K, Temp C, and Sensor, where
K = kelvin, C = degrees Celsius, and Sensor = volts (V) or ohms (Ω). Press the
Enter key.
The Model 331 has two control modes, Closed Loop and Open Loop. Closed Loop control, often called
feedback control, is described in Paragraph 2.6 of this manual. During closed loop control, operation
the Control Input, Setpoint, Heater Range, PID, and Manual Heater Power (MHP) output parameters
are active. Open loop control mode allows the user to directly set the heater output for Loop 1, control
output for Loop 2 with the MHP Output parameter. During Open Loop control only the heater range and
MHP Output parameters are active. To change Control Mode press the
Control Setup key and press
Enter until the following display appears.
Select for Loop 1 °®
Control Mode Closed
The Power Up setting refers to how the control output will respond after the instrument is powered
down. Power Up Enable means the controller will power up with the control output in the same state it
was before power was turned off. Power Up Disable means the controller will always power up with the
heater off no matter how it was set when power was turned off. To change the Power Up parameter
press the Control Setup key and press Enter until the following display appears.
Select for Loop 1 °®
Power Up Disable
Use the s or t key to toggle between Power Up Enable or Disable. Press the Enter key.
The Model 331 will display the heater output as either percent of full scale current or percent of full
scale power for the heater range selected for Loop 1. For Loop 2 the control output is always reported
in percent of full scale voltage and this parameter will not appear in the Control Setup menu. This
parameter affects the heater output display and the scale of the Manual Heater Power (MHP) output
parameter for Loop 1. The MHP Output scale is always the same as the control output display. To
change control output units press the
appears.
Control Setup key and press Enter until the following display
Select for Loop 1 °®
Heater Out Power
Use the s or t key to toggle between Heater Out Power or Current. Press the Enter key.
4-16 Operation
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Lake Shore Model 331 Temperature Controller User’s Manual
4.8 MANUAL TUNING (Closed-Loop PID Control)
In manual PID mode, the controller will accept user-entered Proportional, Integral, and Derivative
parameters to provide three-term PID control. Manual heater power output can be set manually in open
loop and closed loop control modes. For details on PID tuning refer to Paragraph 2.7.
To place the controller in Manual PID tuning mode, press the AutoTune key, and press the s or t key
until you see the following display.
Select for Loop 1 °®
Tune Mode Manual PID
Press the Enter key. The controller is now in Manual PID mode.
4.8.1 Manually Setting Proportional (P)
The proportional parameter (also called gain) is the P part of the PID control equation. It has a range
of 0 to 1000 with a resolution of 0.1. Enter a value greater than zero for P when using closed loop
control.
To set Proportional, press the PID/MHP key. You will see the following display.
Enter for Loop 1
Prop (P) 50.0
The Proportional (gain) limit is entered using the numeric keypad, which includes the numbers 0 – 9,
+/–, and decimal point. Proportional has a range of 0.1 to 1000 with a default of 50. Press the
key, then the
4.8.2 Manually Setting Integral (I)
The integral parameter (also called reset) is the I part of the PID control equation. It has a range of 0
to 1000 with a resolution of 0.1. Setting I to zero turns the reset function off. The I setting is related to
seconds by:
For example, a reset number setting of 20 corresponds to a time constant of 50 seconds. A system
will normally take several time constants to settle into the setpoint. The 50 second time constant, if
correct for the system being controlled, would result in a system that stabilizes at a new setpoint in
between 5 and 10 minutes.
To set Integral, press the PID/MHP key then press Enter until you see the following display.
Escape key to return to the normal display.
I=
setting
1000
I
seconds
Enter
The Integral (reset) is entered using the numeric keypad, which includes the numbers 0 – 9, +/–, and
decimal point. Integral has a range of 0.1 to 1000 with a default of 20. Press the
Escape key to return to the normal display.
Operation 4-17
Enter for Loop 1 I
Integ (I) 20.0
Enter key, then the
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Lake Shore Model 331 Temperature Controller User’s Manual
4.8.3 Manually Setting Derivative (D)
The derivative parameter (sometimes called rate) is the D part of the PID control equation. The rate
time constant should normally be somewhere between 1/4 and 1/8 the integral time in seconds, if
used at all. As a convenience to the operator, the Model 331 Derivative time constant is expressed in
percent of ¼ the integral time. The range is between 0 and 200%. Start with settings of either 0%,
50%, or 100%, and determine which setting gives you the type of control you desire. Do not be
surprised if the setting you prefer is 0. Note that by using a percent of integral time, derivative scales
automatically with changes in the integral value and does not have to be revisited frequently.
To set Derivative, press the PID/MHP key then press Enter until you see the following display.
Enter for Loop 1 D
Deriv (D) 0.0
The Derivative (rate) is entered using the numeric keypad, which includes the numbers 0 – 9, +/–, and
decimal point. Derivative has a range of 0 to 200 percent with a default of 0. Press the
accept the new setting, then the
Escape key to return to the normal display.
4.8.4 Setting Manual Heater Power (MHP) Output
Manual Heater Power (MHP) output is a manual setting of control output. It can function in two
different ways depending on control mode. In open loop control mode, the MHP output is the only
output to the load. The user can directly set control output from the front panel or over computer
interface. In closed loop control mode, the MHP output is added directly to the output of the PID
control equation. In effect, the control equation operates about the MHP output setting.
Manual heater power output setting is in percent of full scale. When using the heater on Loop 1,
percent of full scale is defined as percent of full scale current or power on the selected heater range.
Manual heater power output setting range is 0% to 100% with a resolution of 0.001%.
When using Loop 2 analog voltage output the setting range is 0 to +100% and resolution is 0.001%
but the actual resolution of the output is only 0.003%.
To enter a MHP Output setting, press the PID/MHP key and press Enter until the following display
appears.
Enter for Loop 1
Enter key to
Manual Out 0.00%
The MHP Output setting is entered using the numeric keypad, which includes the numbers 0 – 9, +/–,
and decimal point. Press the
4-18 Operation
Enter key, then the Escape key to return to the normal display.
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Lake Shore Model 331 Temperature Controller User’s Manual
4.9 AUTO TUNE (Closed-Loop PID Control)
The Model 331 automates the tuning process of typical cryogenic systems with the AutoTune feature.
For additional information about the algorithm refer to Paragraph 2.8.
Before initiating AutoTune the cooling system must be set up properly with control sensor and heater
making it capable of closed-loop control. AutoTune works only with one control loop at a time and does
not set the manual heater power output or heater range. The control sensor must have a valid
temperature response curve assigned to it. An appropriate heater range must also be determined as
described in Paragraph 2.7.1. Choosing good initial control parameters by experimenting with Manual
PID tuning can speed up the AutoTune process. If no initial parameters are known start with the default
values of P = 50 and I = 20. It is better to set an initial P value that causes the system to be more active
than desired. Starting with a low P value can increase the time and number of attempts required to
tune.
There are three AutoTune modes available. They result in slightly different system characteristics.
Auto PI is recommended for most applications.
Auto P – Sets only the P parameter value. I and D are set to 0 no matter what the initial values are.
This mode is recommended for systems that have very long lag times or nonlinearity that prevents
stable PI control. Expect some overshoot or undershoot of the setpoint and stable temperature
control below the setpoint value.
Auto PI – Sets values for both P and I parameters. D is set to zero. This mode is recommended for
stable control at a constant temperature. It may take slightly longer to stabilize after setpoint change
than Auto PID. Expect some overshoot or undershoot of the setpoint and stable temperature control
at the setpoint value.
Auto PID – Sets values for P, I and D parameters. D is always set to 100%. This mode is
recommended when setpoint changes are frequent but temperature is allowed to stabilize between
changes. Stability at setpoint may be worse than Auto PI in noisy systems. Expect slightly less
overshoot or undershoot than the other modes and control at the setpoint value.
Once AutoTune mode is selected, the Tune annunciator turns on steady to indicate that AutoTune is
on. No activity takes place until the setpoint is changed at least 0.5 K. At that time, the Tune
annunciator blinks to indicate the instrument is gathering data. This process takes from 1 to 17 minutes
depending on the system reaction time. The tune annunciator stops blinking when calculations are
complete and new parameter values have been stored. The annunciator will also stop blinking if the
algorithm is unable to complete. Possible reasons include: setpoint change too small, manual control
parameter changed during tuning, heater not turned on, or control sensor curve not selected.
If the controller is not tuned satisfactorily on the first attempt, make several small (2 degree) setpoint
changes to see if better parameter values are calculated.
To select an AutoTune mode press the AutoTune key, and press either the s, t, or AutoTune key to
cycle the display to AutoTune PID. You will see the following display.
Use the s or t key to cycle between Auto PID, Auto PI, and Auto P. Press the Enter key. The
controller is now in Autotuning mode. When the AutoTune feature is on, the front panel
be on steady. When there is a setpoint change and the Model 331 is actively gathering data, the
LED will blink.
Operation 4-19
Select for Loop 1 °®
Tune Mode Auto PID
Tune LED will
Tune
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Lake Shore Model 331 Temperature Controller User’s Manual
4.10 ZONE SETTINGS (Closed-Loop Control Mode)
The Model 331 allows the user to establish up to 10 custom contiguous temperature zones where the
controller will automatically use pre-programmed PID values and heater ranges. Zone control can be
active for both control loops at the same time. The user should configure the zones using 01 as the
lowest to 10 as the highest zone. Zone boundaries are always specified in kelvin (K). The bottom of the
first zone is always 0 K, therefore, only the upper limit is required for all subsequent zones. Make a
copy of Figure 4-4 to plan your zones.
Once all zone parameters have been programmed, the controller must be placed in zone tuning mode.
To do this, press the
AutoTune key. Use the s or t key to select Zone. Then press Enter to accept
the new tuning mode. Once zone is turned on, the instrument will update the control settings each time
the setpoint is changed to a new zone. If the settings are changed manually, the controller will use the
new setting while it is in the same zone and update to the zone table settings when the setpoint is
changed to a value outside that zone.
To enter parameter values into the zone table, press the Zone Settings key. You will see the following
display.
Select for Loop 1 °®
Zone 01
Use the s or t key to cycle through the ten zones. Once the desired zone is displayed, press the
Enter key. You will see the next display.
Enter for Zone 01
SP Limit 0.0000½
The upper setpoint limit is entered using the numeric keypad, which includes the numbers 0 – 9, +/–,
and decimal point. During numeric entry, you can press the
a second time to exit to the normal display.
NOTE: The default setting for all the zone setpoints is zero (0). The Model 331 will not search
for additional zones once it encounters a setpoint of zero.
Press the Enter key to accept the new upper limit. You will see the next display.
Escape key one time to clear the entry, and
Enter for Zone 01
Prop (P) 50.0
The Proportional (P) value is entered using the numeric keypad, which includes the numbers 0 – 9, +/–,
and decimal point. Proportional has a range of 0.1 to 1000 with a default of 50. Press the
accept the new setting. You will see the next display.
Enter key to
4-20 Operation
Page 67
Zone Settings (Continued)
Lake Shore Model 331 Temperature Controller User’s Manual
Enter for Zone 01
Integ (I) 20.0
The Integral (I) value is entered using the numeric keypad, which includes the numbers 0 – 9, +/–, and
decimal point. Integral has a range of 0.1 to 1000 with a default of 20. Press the
Enter key to accept the
new setting. You will see the next display.
Enter for Zone 01
Deriv (D) 0.0
The Derivative (D) value is entered using the numeric keypad, which includes the numbers 0 – 9, +/–,
and decimal point. Derivative has a range of 0 to 200 percent with a default of 0. Press the
accept the new setting. You will see the next display.
Enter key to
Enter for Zone 01
Manual Out 0.00%
The MHP Output setting is entered using the numeric keypad, which includes the numbers 0 – 9, +/–,
and decimal point. Manual heater has a range of 0.001 to 100 percent with a default of 0. Press the
Enter key to accept the new heater setting. Assuming the zone is controlling using Loop 1, you will see
the next display.
Select for Zone01 °®
Heater Range Off
Use the s or t key to select the Heater Range: High, Medium, Low, or Off. Press the Enter key to
accept the new heater range and return to the normal display. (If you are controlling using Loop 2, the
last heater range setting is omitted.) This completes the setting of Zone 01. Repeat the process for the
subsequent zones.
Operation 4-21
Page 68
Lake Shore Model 331 Temperature Controller User’s Manual
Zone Setting WorkSheet
Zone 10
Proportional
(0.1-1000)
Integral
(0.1-1000)
Derivative
(0-200)
MHP Output
(0-100%)
Heater Range
Off Low Med High
Zone 09
Proportional
(0.1-1000)
Integral
(0.1-1000)
Derivative
(0-200)
MHP Output
(0-100%)
Heater Range
Off Low Med High
Zone 08
Proportional
(0.1-1000)
Integral
(0.1-1000)
Derivative
(0-200)
MHP Output
(0-100%)
Heater Range
Off Low Med High
Zone 07
Proportional
(0.1-1000)
Integral
(0.1-1000)
Derivative
(0-200)
MHP Output
(0-100%)
Heater Range
Off Low Med High
Zone 06
Proportional
(0.1-1000)
Integral
(0.1-1000)
Derivative
(0-200)
MHP Output
(0-100%)
Heater Range
Off Low Med High
Zone 05
Proportional
(0.1-1000)
Integral
(0.1-1000)
Derivative
(0-200)
MHP Output
(0-100%)
Heater Range
Off Low Med High
Zone 04
Proportional
(0.1-1000)
Integral
(0.1-1000)
Derivative
(0-200)
MHP Output
(0-100%)
Heater Range
Off Low Med High
Zone 03
Proportional
(0.1-1000)
Integral
(0.1-1000)
Derivative
(0-200)
MHP Output
(0-100%)
Heater Range
Off Low Med High
Zone 02
Proportional
(0.1-1000)
Integral
(0.1-1000)
Derivative
(0-200)
MHP Output
(0-100%)
Heater Range
Off Low Med High
Zone 01
Proportional
(0.1-1000)
Integral
(0.1-1000)
Derivative
(0-200)
MHP Output
(0-100%)
Heater Range
Off Low Med High
0 K
C331-4-4.eps
Setpoint:
Setpoint:
Setpoint:
Setpoint:
Setpoint:
Setpoint:
Setpoint:
Setpoint:
Setpoint:
Setpoint:
0 K
Figure 4-4. Record of Zone Settings
K
K
K
K
K
K
K
K
K
K
4-22 Operation
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Lake Shore Model 331 Temperature Controller User’s Manual
4.11 SETPOINT
The control setpoint is the desired load temperature expressed in temperature or sensor units. Use
sensor units if no temperature response curve is selected for the sensor input used as the control
channel.
The control setpoint has its own units parameter. Set with the Control Setup key in Paragraph 4.7.
Control channel readings can display in any units. Display units need not match setpoint units.
NOTE: If a curve is not assigned to the control input, control reverts to sensor units and the
setpoint is set to the most current reading.
When changing setpoint units while the control loop is active, the Model 331 converts the control
setpoint to the new control units for minimal disruption in control output.
Setpoint resolution depends on sensor type and setpoint units. With setpoint expressed in temperature,
setpoint resolution is 0.001 degree for setpoints below 100, and 0.01 for setpoints between 100 and
1000. In sensor units, the setpoint resolution matches the display resolution for the sensor input type
given in the specifications (Table 1-3).
The instrument allows a large setpoint range to accommodate a variety of sensors and units. With
setpoint expressed in sensor units, setpoint range is unlimited. The user must determine suitability of a
setpoint value. In temperature units, a safety feature limits the setpoint value to help prevent load
damage load. The setpoint limit in the temperature response curve sets maximum safe temperature in
kelvin for the sensor package. It can be verified by using the Curve Entry key. The setpoint is limited to
a value less than or equal to the limit. If the setpoint value changes from the number entered when
Enter is pressed, it is likely the setpoint exceeds the above limit or is inappropriate for the sensor type.
Once control setup parameters are configured (Paragraph 4.7) and the active control loop is selected
(Paragraph 4.6.1), the desired temperature setpoint is entered by pressing the
Setpoint key.
Enter for Loop 1
Setpoint +77.350½
The setpoint is entered using the numeric keypad, which includes the numbers 0 – 9, +/–, and decimal
point. Press the
If the display format is configured to show the setpoint (Paragraph 4.3), you will see something
resembling the following for a normal display.
Enter key to accept the new setpoint or press the Escape key to cancel.
À 77.236½ Á 295.22½
 77.350½ 50% Low
Operation 4-23
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Lake Shore Model 331 Temperature Controller User’s Manual
4.12 RAMP
The Model 331 generates a smooth setpoint ramp when the setpoint units are expressed in
temperature. The user can set a ramp rate in degrees per minute with a range of 0 to 100 and a
resolution of 0.1. Once the ramp feature is turned on, its action is initiated by a setpoint change. When
a new setpoint is entered, the instrument changes the setpoint temperature from the old value to the
new value at the ramp rate. A positive ramp rate is always entered and it is used by the instrument for
ramps up and down in temperature.
The ramping feature is useful by itself but it is even more powerful when used with other features.
Setpoint ramps are often used with zone control mode. As temperature is ramped through different
temperature zones, control parameters are automatically selected for best control. Ramps can be
initiated and status read back using a computer interface. During computer controlled experiments, the
instrument generates the setpoint ramp while the computer is busy taking necessary data. AutoTune
does not function during a setpoint ramp. The ramp rate disguises the reaction of the cooling system
and no valid tuning data can be taken.
NOTE: When an incomplete ramp is shut off, the setpoint will remain on the most current
setting, i.e., the reading will not jump to the end of the ramp.
NOTE: If the input type or input curve is changed while a ramp is in progress, both ramping
and the heater are turned off.
NOTE: If Ramp is on and the setpoint is set to sensor units, the ramping function will remain on but
when another setpoint is entered, the setpoint goes directly to the new setpoint value. The
Ramp LED will stay on solid (no blinking).
To enable setpoint ramping, press the Control Setup key, then press the Enter key until you see the
following display.
Select for Loop 1 °®
Setpoint Ramp On
Use the s or t key to select Setpoint Ramp On. Press the Enter key. You will see the following.
Enter for Loop 1
Ramp Rate 0.0 K/m
The ramp rate is entered using the numeric keypad, which includes the numbers 0 – 9 and decimal
point. The user can set a ramp rate in degrees per minute with a range of 0 to 100 and a resolution of
0.1. Ramp rate will be in the same units specified for the setpoint. Press the
Ramp LED will illuminate, indicating the ramp function is active. Any subsequent change in setpoint will
ramp at the specified rate and the
If you wish to pause a ramp, press the Setpoint key then immediately press the Enter key. This stops
the ramp at the current setpoint but leaves the ramping function activated. Then to continue the ramp,
enter a new setpoint.
To turn the ramping feature off, press the Control Setup key, then press the Enter key until you see the
following screen.
Ramp LED will blink while ramping is in progress.
Enter key. The front panel
Select for Loop 1 °®
Setpoint Ramp Off
Use the s or t key to select Setpoint Ramp Off. Press the Enter key then the Escape key. The Ramp
LED will turn off.
4-24 Operation
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Lake Shore Model 331 Temperature Controller User’s Manual
4.13 HEATER RANGE AND HEATER OFF
Heater output for Loop 1 is a well-regulated variable DC current source. The Heater output is optically
isolated from other circuits to reduce interference and ground loops. The Heater output for the main
control loop (Loop 1) can provide up to 50 W of continuous power to a resistive heater load and
includes two lower ranges for systems with less cooling power. Heater output is short-circuit protected
to prevent instrument damage if the heater load is accidentally shorted.
Loop 1 Full Scale Heater Power at Typical Resistance
Heater Resistance Heater Range Heater Power
10 Ω
25 Ω
50 Ω
Low
Med
High
Low
Med
High
Low
Med
High
100 mW
1 W
10 W
250 mW
2.5 W
25 W
500 mW
5 W
50 W
NOTE: During normal operation, if the input type or input curve is changed for the control
input, the heater will automatically shut off.
A common error condition that may appear is “HTR Open.” This error message will appear when the
heater senses there is no load connected to the rear panel terminals. The user can correct this problem
by properly connecting a heater load. It could also indicate a malfunction internal to the Model 331,
such as a loose connection or a malfunctioning component, but this is much less likely. Other error
messages are summarized in Paragraph 8.8.
Specifications of heater output are provided in Paragraph 1.X – Instrument Specifications. Heater
theory of operation is provided in Paragraph 2.4 – Heater Selection and Installation. Various Heater
installation considerations are provided in Paragraph 3.7 – Heater Output Setup.
The Model 331S only has the additional ability to configure the analog output as a variable DC voltage
source capable of a 1 W output.
Once control setup parameters are configured (Paragraph 4.7), and the active control loop is selected
(Paragraph 4.6.1), the desired heater range is selected by pressing the
Heater Range key.
Use the s or t key to cycle through Loop 1 Heater settings: Off, Low, Med, and High. Once the
desired heater setting is displayed, press the
For the Model 331S only, use the s or t key to toggle between Loop 2 Heater settings: Off and On.
Once the desired heater setting is displayed, press the
NOTE: If the display shows Heater Disabled, the analog output does not have the proper
parameter configuration to work as a control loop. Refer to Paragraph 4.16.
To immediately turn the heater off, press the Heater Off key. If the Heater Range is not being displayed
on the front panel, the user should immediately press the
loop is displayed and the heater shows Off.
Operation 4-25
Select for Loop 1 °®
Heater Range Off
Enter key. You will return to the normal display.
Enter key. You will return to the normal display.
Heater Range key to verify that the proper
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Lake Shore Model 331 Temperature Controller User’s Manual
4.14 MATH
Three math features are included for convenience and aid in setting up experiments. Max and Min
readings can be captured. A linear equation can be applied to input data to correct system errors or
improve performance of the analog outputs. Readings can be filtered to quiet effects of a noisy
environment. These math features can be performed on both sensor inputs, however, each input must
be configured separately.
When you first press the Math key, you will see the following display.
Press Math to Reset,
Enter to Continue
Press the Math key again to reset the stored maximum and minimum values. This does not reset the
math settings, it only resets the data that has been collected since the function was initiated or since the
last math reset. The controller will return to the normal display. Otherwise, press the
continue to the math settings. The first screen appear as follows.
Enter key to
Select With °®
Math Setup Input A
Use the s or t key to toggle between Input A and B. Press the Enter key to accept, or press the
Escape key to cancel the entry and return to the normal display. All subsequent math functions will be
set for the selected input. The following paragraphs detail the math settings in order of appearance.
4.14.1 Max/Min
The Max/Min feature captures and stores the highest (Max) and lowest (Min) reading taken since the
last reset. The feature will only capture from one reading source at a time for each input. Temp K,
Temp C, Sensor, and Linear selection determines the source for the selected sensor input:
Temp K Kelvin temperature reading from input.
Temp C Celsius temperature reading from input.
Sensor Sensor units (V, mV, or Ω) reading from input.
Linear Linear (/) equation data from input.
Max and Min are always being captured, so there is no need to turn the feature on or off. The
readings are reset when the instrument is turned off, parameters related to the input are changed, or
the Math/Reset sequence is performed.
To select a source for Max/Min continue from the Math Setup screen in Paragraph 4.14, press the
Enter key to see the following display.
Select for Math A °®
Mx/Mn Source Temp K
Use the s or t key to cycle through the data sources. The user must select a source for the Max/Min
feature. After selecting the desired source, press the
return to the normal display. The instrument retains values entered prior to pressing the
Press the Math key twice to reset Max/Min. Max/Min automatically resets when the instrument is
turned off or parameters related to the input change.
4-26 Operation
Enter key. Press the Escape key at any time to
Escape key.
Page 73
4.14.2 Linear
The Model 331 will process either of two simple linear equations for each sensor input: MX+B or
M(X+B). The result can be displayed or directed to the analog voltage output.
There are two different equations available. In each: M is a gain or slope, X is an input reading, and B
is an offset or intercept (not to be confused with input B). The two equations are shown in Table 4-4.
The difference between them is subtle. The first equation is used to scale the raw reading of an input,
similar to a temperature response curve, when the sensor has linear response. The second is better
at generating a control signal when a setpoint (SP1 or SP2) is selected as B. The control signal can
then be directed to an analog output. The second equation is also useful whenever a reading of
deviation from setpoint is needed.
The columns settings in Table 4-4 are selected independently. “Number” represents a number
entered by the user. “X” can be set to an input reading in sensor units or temperature in kelvin or
Celsius. SP1 represents setpoint of Loop 1 and similarly for other B settings.
NOTE: When using the linear equations MX+B or M(X+B), the user should ensure that the
To configure a linear equation continue from the math setup screen in Paragraph 4.14 and press the
Enter key until the following display appears.
Lake Shore Model 331 Temperature Controller User’s Manual
Table 4-4. Linear Equation Configuration
Equation M X B
M X + B
M (X + B)
Number Sensor
Temp K
Temp C
Number
+SP1
-SP1
+SP2
-SP2
setpoint and “x” variable units match. If the units do not match, the instrument will
continue calculations, but results may not be what is expected.
Select for Math A °®
Linear Equ MX+B
Use the s or t key to toggle between the two linear equations: MX+B or M(X+B), where:
M = slope of a line, X = reading data from a sensor input, and B = offset of a line.
Enter for Math A
Lin Equ M +0.0000
The Linear Variable M is entered using the numeric keypad, which includes the numbers 0 – 9, +/–,
and decimal point. Press the
Enter key to accept the new setting. You will see the next display.
Select for Math A °®
X Source Temp K
Use the s or t key to toggle between the Linear X Variable: Temp C, Temp K, Sensor. Press the
Enter key to accept the new setting. You will see the next display.
Select for Math A °®
B Source Value
Operation 4-27
Page 74
Linear (Continued)
Use the s or t key to toggle between the Linear B Variable: +SP1, –SP1, +SP2, –SP2, Value.
Press the
Lake Shore Model 331 Temperature Controller User’s Manual
Enter key to accept the new setting. You will see the next display.
Enter for Math A
The Linear Variable B is entered using the numeric keypad, which includes the numbers 0 – 9, +/–,
and decimal point. Press the
Press the Escape key to return to the normal display or continue with the Filter settings (Paragraph
4.14.3).
4.14.3 Filter
The reading filter applies exponential smoothing to the sensor input readings. If the filter is turned on
for a sensor input, all reading values for that input are filtered. The filter is a running average so it
does not change the update rate of an input. Filtered readings are not used for control functions but
they are used for all input features including Max/Min.
The number of filter points determines how much smoothing is done. One filter point corresponds to
one new reading on that input. A larger number of points does more smoothing but also slows the
instruments response to real changes in temperature. The default number of filter points is 8 which
settles in approximately 50 readings or 5 seconds.
The filter window is a limit for restarting the filter. If a single reading is different from the filter value by
more than the limit the instrument will assume the change was intentional and restart the filter. Filter
window is set in percent of full scale range.
To configure a filter, continue from the Math Setup screen in Paragraph 4.14, press the Enter key
until the following display appears.
Lin Equ B +0.0000
Enter key to accept the new setting.
Select for Math A °®
Filter On
Use the s or t key to toggle between Filter On and Off. If you select Off, the routine will end and
return you to the normal display. If you select On, the routine will continue with the following.
Select for Math A °®
Filter Points 08
Use the s or t key to increment or decrement the Filter Points from 02 thru 64, with 08 being the
default. Press the
Enter key. You will see the following display.
Select for Math A °®
Filter Window 01%
Use the s or t key to increment or decrement the Filter Window from 01% thru 10%, with 01% being
the default. Press the
4-28 Operation
Enter key. You will return to the normal display.
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Lake Shore Model 331 Temperature Controller User’s Manual
4.15 ALARMS AND RELAYS (Model 331S Only)
4.15.1 Alarms
Each input of the Model 331 has high and low alarm capability for each input. Input reading data from
any source can be compared to the alarm setpoint values. A reading higher than the high setpoint
triggers the high alarm for that input. A reading lower than the low alarm setpoint triggers the low
alarm for that input.
The Alarm annunciator steadily displays when any alarm is enabled; it flashes when any alarm
activates. An input need not display for the system Alarm annunciator to indicate input alarm status.
The beeper inside the instrument can also be programmed to sound if any alarms activate. The two
relays on a 331S can also be tied to alarm functions as described below.
Latching Alarms – Often used to detect faults in a system or experiment that require operator
intervention. The alarm state remains visible to the operator for diagnostics even if the alarm
condition is removed. Relays often signal remote monitors or for added safety take critical
equipment off line. Pressing the
Alarm key clears latched alarms.
Non-Latching Alarms – Often tied to relay operation to control part of a system or experiment. The
alarm state follows the reading value. The dead band parameter can prevent relays from turning on
and off repeatedly when the sensor input reading is near an alarm setpoint.
alarm setpoint = 100 K and the dead band = 1 K, the high alarm triggers when sensor input
temperature increases to 100 K, and it will not deactivate until temperature drops to 99 K. Figure 45 illustrates the interaction between alarm setpoint and dead band.
In Figure 4-5, with the high alarm setpoint at 100 K and the dead band at 5 K, the high alarm triggers
when sensor input temperature increases to 100 K, and it will not deactivate until temperature drops
to 95 K. In addition, the same 5 K dead band is applied to the low alarm setpoint as well.
High Alarm Activated
Example: If the high
High Alarm Deactivated
High Alarm Setpoint
100 K
95 K
Temperature Reading
Alarm Latching Off
Deadband = 5 K
Low Alarm Setpoint
Low Alarm Activated
Low Alarm Deactivated
55 K
50 K
Figure 4-5. Deadband Example
To begin alarm setup, press the
Alarm key.
Select With °®
Alarm Setup Input A
Use the s or t key to toggle between Input A and B. Press the Enter key.
Operation 4-29
Page 76
Alarms (Continued)
Lake Shore Model 331 Temperature Controller User’s Manual
Select for Alm A °®
Alarm On
Use the s or t key to toggle between Alarm On or Off. Press the Enter key.
Select for Alm A °®
Source Temp K
Use the s or t key to cycle through the following data sources: Temp C, Temp K, Linear, or Sensor,
where Temp C = degrees Celsius, Temp K = kelvin, Linear = MX+B or M(X+B) (refer to Paragraph
4.14.2), or Sensor = volts (V), millivolts (mV) or ohms (Ω). Press the
Enter key.
Enter for Alarm A
Alarm Low 50½
The Low Alarm Point is entered using the numeric keypad, which includes the numbers 0 – 9, +/–, and
decimal point. For this example, enter 50 K. Press the
Enter key.
Enter for Alarm A
Alarm High 100½
The High Alarm Point is entered using the numeric keypad, which includes the numbers 0 – 9, +/–,
and decimal point. For this example, enter 100 K. Press the
Enter key.
Select for Alm A °®
Alarm Latching Off
Use the s or t key to toggle between Latching On or Off. For this example, select Alarm Latching
Off. Press the
Enter key.
Enter for Alarm A
Dead Band 5½
The dead band is entered using the numeric keypad, which includes the numbers 0 – 9, +/–, and
decimal point. Press the
will sound when an alarm is active. This is a global parameter so it is set once for all alarms.
After specifying either Alarm Setpoint On or Dead Band, next is the Alarm Audible screen.
Enter key. The audible parameter determines whether the internal beeper
Select With °®
Alarm Audible On
Use the s or t key to toggle between Audible Alarm On or Off. For this example, select Audible
Alarm On. Press the
Enter key.
4-30 Operation
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Lake Shore Model 331 Temperature Controller User’s Manual
4.15.2 Relays (331S Only)
There are two relays on the Model 331S numbered 1 and 2. They are most commonly thought of as
alarm relays, but may be manually controlled also. Relay assignments are configurable as shown in
Figure 4-6.Two relays can be used with one sensor input for independent high and low operation.
When using relays with alarm operation, set up alarms first. The relays are rated for 30 VDC and 5 A.
Their terminals are in the detachable terminal block on the Model 331S rear panel.
To configure Relay 1 press the Alarm key and press Enter until the following display appears.
Select With °®
Relay 1 A Alarm
Use the s or t key to cycle through the options for Relay 1: Off, On, A Alarm, or B Alarm. Press the
Enter key. If the relay is set to follow either the A or B Alarm, the following screen will appear.
Select With °®
Relay 1 High Alarm
Use the s or t key to cycle through the relay alarm functions: Low Alarm, High Alarm, and Both
Alarms. Press the
Configuration for Relay 2 is identical to Relay 1.
OffOff
Manual Off
relay remains in
normal state
Enter key.
Relay 1Relay 1
OnOn
Manual On
relay remains in
active state
Alarms
Both
A AlarmA Alarm
Follows
A
Input
B AlarmB Alarm
Low
Alarm
Relay SettingsRelay Settings
Follows
B
Input
High
Alarm
Manual Off
relay remains in
normal state
OffOff
Relay 2Relay 2
OnOn
Manual On
relay remains in
active state
Alarms
Both
A AlarmA Alarm
Follows
A
Input
Alarm
B AlarmB Alarm
Low
Follows
B
Input
High
Alarm
Off Manual Off. Relay remains in the normal state.
On Manual On. Relay remains in the active state.
A Alarm Relay will follow Input A alarms.
Both Alarms Relay active when either the High or Low Alarm is active.
Low Alarms Relay active only when the Low Alarm is active.
High Alarms Relay active only when the High Alarm is active.
B Alarm Relay will follow Input B alarms.
Both Alarms Relay active when either the High or Low Alarm is active.
Low Alarms Relay active only when the Low Alarm is active.
High Alarms Relay active only when the High Alarm is active.
Operation 4-31
Figure 4-6. Relay Settings
Page 78
Lake Shore Model 331 Temperature Controller User’s Manual
4.16 ANALOG OUTPUT (Model 331S Only)
The Model 331S has a single analog output on Pins 7 and 8 of the terminal block at the rear of the
instrument. It is normally configured to send a voltage proportional to temperature to a strip chart
recorder or separate data acquisition system. The output can also be manually controlled as a voltage
source for any other application or used as the control output for Loop 2.
The analog output is a variable DC voltage source that can vary from +10V to –10V. The voltage is
generated by a 16-bit D/A converter with resolution of 0.3 mV or 0.003% of full scale. The output is
short-circuit protected but should never be used to drive a resistance lower than 100 Ω. When acting as
the Loop 2 heater, the output can provide up to 1 W of power (0.1 A into a 100 Ω minimum heater load).
For further specifications, refer to the Loop 1 and 2 comparison table in Paragraph 1.X.
The analog output has four modes of operation: Off, Input, Manual, and Loop 2. If you select Off, the
analog output is set to 0 volts and you are returned to the normal display. Once a mode is selected, the
parameters associated with that mode follow on setting screens.
4.16.1 Analog Output In Input Mode
In Input mode, the analog output will track the input according to scaling parameters entered by the
user. Press the
Analog Output key.
Select with °®
Analog Out Input A
Press the s or t key until Input A is showing. Press the Enter key.
Select for AnOut °®
Source Temp K
Press the s or t key to cycle through the data source units: Temp K, Temp C, Sensor, or Linear,
where K = kelvin, C = Celsius, Sensor = volts (V) or ohms (Ω), and Linear = MX+B or M(X+B) (refer
to Paragraph 4.14.2). For this example, choose Temp K. Press the
Enter key.
Select for AnOut °®
Bipolar Mode On
Press the s or t key to toggle between Bipolar Mode On or Off.
4-32 Operation
Page 79
Analog Output In Input Mode (Continued)
Lake Shore Model 331 Temperature Controller User’s Manual
Bipolar mode refers to whether or not negative voltages are used, as shown below.
Bipolar Mode: OnBipolar Mode: On
Input ModeInput Mode
Bipolar Mode: OffBipolar Mode: Off
For this first example we will choose Bipolar Mode On. Press the Enter key.
Enter for AnOut
Lowest
10 V
Lowest
0 V
Input
Output
Middle
0 V
Middle
+5 V
Input
Output
Highest
+10 V
Highest
+10 V
-10V Value 0½
The –10 V value is entered using the numeric keypad, which includes the numbers 0 – 9, +/–, and
decimal point. For this example, we will enter 0 K. Press the
Enter key.
Enter for AnOut
+10V Value 100½
The +10 V value is entered using the numeric keypad, which includes the numbers 0 – 9, +/–, and
decimal point. For this example, we will enter 100 K. Press the
normal display.
The analog output will now correspond to the input temperature as shown below. For example, if the
actual reading was 50 K, the analog output would be at 0 V (middle of the scale).
0 K 50 K
Bipolar Mode: OnBipolar Mode: On
10 V
If we repeat the same procedure using all the same settings, but select Bipolar Mode Off, the output
would be as shown below. In this case, if the actual reading was 50 K, the analog output would be
+5 V (middle of the scale).
0 K
Bipolar Mode: OffBipolar Mode: Off
0 V
Input
Output
Input
Output
Enter key. You are returned to the
100 K
0 V
50 K
+5 V
+10 V
100 K
+10 V
Operation 4-33
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Lake Shore Model 331 Temperature Controller User’s Manual
4.16.2 Analog Output In Manual Mode
In Manual mode, the analog output provide a fixed output according to a percentage of full scale
entered by the user; -100.00% to +100.00% corresponding to –10 V to +10 V. The setting resolution
on the display is 0.001% but the output itself is limited to 0.003%. Press the
Select With °®
Analog Output key.
Analog Out Manual
Press the s or t key until “Manual” is showing. Press the Enter key.
Select for AnOut °®
Bipolar Mode On
Press the s or t key to toggle between Bipolar Mode On or Off. Bipolar mode refers to whether or
not negative voltages are used, as shown below.
100%
Bipolar Mode: On
10 V
Manual Mode
Bipolar Mode: Off
For this example, we will choose Bipolar Mode On. Press the Enter key.
User Entry
Output
0%
0 V
0%
0 V
+100%
+10 V
User Entry
Output
+100%
+10 V
Enter for AnOut
Manual Out - 50%
The desired fixed output you want as a percent of full scale is entered using the numeric keypad,
which includes the numbers 0
Enter key. The instrument will return to the normal display. The analog output will begin to output
the
– 9, +/–, and decimal point. For this example, we will enter –50%. Press
a constant voltage that is –50% × 10 volts = –5 volts.
In a second example, if you repeat the same procedure using all the same settings, but enter +75%,
then the output would be +75% × 10 volts = +7.5 volts.
In a third example, if you repeat the same procedure, but choose Bipolar Off, enter +25%, then the
output would be +25% × 10 volts = +2.5 volts. The difference being that any negative sign will be
ignored with Bipolar Mode Off and the output will always be a positive voltage.
4-34 Operation
Page 81
Lake Shore Model 331 Temperature Controller User’s Manual
4.16.3 Analog Output In Loop 2 Mode
In Loop 2 mode, the analog output is directly controlled by Model 331. To place the analog output in
Loop 2 mode, press the
Analog Output key, then press the s or t key until you see the following
display.
Select With °®
Analog Out Loop 2
Press the Enter key. The next screen is for control of Bipolar Mode.
Select for Loop 2 °®
Bipolar Mode Off
Press the s or t key to toggle between Bipolar Mode Of or Off. Bipolar Mode On allows the control
output to go negative. This is only needed when controlling a thermoelectric device. For most cases,
Bipolar Mode should be Off. Press the
4.17 LOCKING AND UNLOCKING THE KEYPAD
The keypad lock feature prevents accidental changes to parameter values. When the keypad is locked,
some parameter values may be viewed, but most cannot be changed from the front panel. Alarm Reset
and Heater Off are the only keypad functions that remain active when the keypad is locked.
A 3-digit keypad lock code locks and unlocks the keypad. The factory default code is 123. The code can
be changed only through the computer interface. If instrument parameters are reset to default values,
the lock code resets also. The instrument cannot reset from the front panel with the keypad locked.
To lock the keypad, press and hold the Enter key for 10 seconds to display the screen shown as
follows.
Enter key. The instrument returns to the normal display.
Enter Code To
Lock Keypad
Use the numeric keypad to enter the 3-digit lock code. The keypad locks and the normal display
appears. Changes attempted to any parameters result in a brief display of the *LOCKED* message.
To unlock the keypad, press and hold the Enter key for 10 seconds to display the screen shown as
follows.
Enter Code To
Unlock Keypad
Use the numeric keypad to enter the 3-digit lock code. The keypad unlocks and the normal display
again appears. All Model 331 parameters are now accessible.
Operation 4-35
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Lake Shore Model 331 Temperature Controller User’s Manual
4.18 DISPLAY BRIGHTNESS
The user is able to control the brightness of the vacuum fluorescent display. Press and hold the
Display Format key for several seconds until you see the following display.
Select With °®
Brightness 75%
Use the s or t key to select 25%, 50%, 75%, or 100%. Press the Enter key. The instrument returns to
the normal display.
CAUTION: Prolonged use of the display brightness on the 100% setting will reduce the life of
the vacuum fluorescent display.
4.19 REMOTE/LOCAL
“Local” refers to operating the Model 331 from the front panel. “Remote” refers to operating the
controller via the IEEE-488 Interface. They keypad is disabled during remote operation. The mode of
operation can be changed by pressing the
Remote/Local key. When in the Local mode, the Remote
LED in the upper right-hand corner of the front panel will be Off. When in the Remote mode, the
Remote LED will be On.
4.20 INTERFACE
The Interface key serves three functions: set the Serial Interface Baud rate, set the IEEE-488 Interface
Address and Terminators (Model 331S Only), and select the Model 330 Emulation Mode.
To set the Serial Interface Baud rate, press the Interface key.
Select With °®
Baud 9600
Use the s or t key to cycle through the choices of 300, 1200, and 9600 Baud. The default Baud rate is
9600. Press the
return to the normal display.
On the Model 331S only, to set the IEEE-488 Interface Address and Terminators, press the Interface
key, then press the
Enter key to accept the changes or the Escape key to keep the existing setting and
Enter key until you see the following screen.
Select With °®
IEEE Address 12
Use the s or t key to increment or decrement the IEEE Address to the desired number. The default
address is 12. Press the
setting and return to the normal display. Press the
Enter key to accept the changes or the Escape key to keep the existing
Select With °®
IEEE Term Cr Lf
4-36 Operation
Enter key again to see the following screen.
Page 83
Interface (Continued)
Lake Shore Model 331 Temperature Controller User’s Manual
Use the s or t key to cycle through the following Terminator choices: Cr Lf, Lf Cr, Lf, or EOI, where
Cr = Carriage Return, Lf = Line Feed, and EOI = End Or Identify. The default terminator is Cr Lf.
Press the
the existing setting and return to the normal display.
Enter key to accept the changes and continue to the next screen, or the Escape key to keep
Select With °®
Emulation Mode 331
Use the s or t key to toggle between 331 and 330. The default setting is 331. If 331 mode is selected,
pressing the
Enter key will return you to the normal display.
To support owners of the Lake Shore Model 330 Temperature Controller, 330 Emulation Mode is
provided. The 330 Emulation Mode only affects remote operation; front panel operation of the Model
331 is not changed. In 330 Emulation Mode, curve locations are mapped to match Model 330 locations.
For example, the DT-500-D Curve, found at curve location 3 in the Model 331, is mapped to location 0
when in 330 mode. This applies to the following remote commands: ACUR, ACUR?, BCUR, BCUR?.
The following Model 330 commands are not supported in 330 Emulation Mode: CUID?, CURV, CURV?,
ECUR, KCUR, and SCAL. Please refer to your Model 330 User’ s Manual for any additional questions
concerning remote commands.
Selecting 330 Emulation Mode causes two additional screens to appear.
Select With °®
Sample Channel A
Use the s or t key to toggle between Sample Channel A or B. The default setting is A. Press the
Enter key. You will see the following display.
Select With °®
Sample Units K
Use the s or t key to cycle through the Sample Units: K, C, and Sensor, where K = kelvin,
C = degrees Celsius, and Sensor = volts (V) or ohms (Ω). The default setting is K. Press the
Enter key.
You will return to the normal display.
4.21 DEFAULT VALUES
It is sometimes necessary to reset instrument parameter values or clear out the contents of curve
memory. Both are all stored in nonvolatile memory called NOVRAM but they can be cleared
individually. Instrument calibration is not affected except for Room Temperature Calibration which
should be redone after parameters are set to default values or any time the thermocouple curve is
changed.
To reset the Model 331 parameters to factory default values, press and hold the
screen shown below appears.
Escape key until the
Code Date: 06/01/00
Default Values Yes
Operation 4-37
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Lake Shore Model 331 Temperature Controller User’s Manual
Default Values (Continued)
Use the s or t key to select Yes or No to reset the NOVRAM. Select Yes to reset all Model 331
parameters to the defaults listed in Table 4-5. Press the
Enter key. The second screen appears as
follows.
Input Version 1.0
Clear Curves No
Use the s or t key to select Yes or No to clear the user curves (in locations 21 – 41) stored in the
Model 331. Standard curves (in locations 1
– 20) are unaffected. Press the Enter key. The instrument
performs the operation then returns to the normal display.
Table 4-5. Default Values
Alarm and Relay
Alarm ............................ Off
Alarm Audible ............... Off
Relay 1 ......................... Off
Relay 2 ......................... Off
Analog Output
Analog Output .............. Off
Control Setup
Control Input ................ Input A
SP Units ....................... Temp K
Control Mode ............... Closed
Power Up ..................... Disable
Setpoint Ramp ............. Off
Heater Output Display .. Current
Display Format
Display Location 1 ........ Input A / Temp K
Display Location 2 ........ Input B / Temp K
Display Location 3 ........ Setpoint
Display Location 4 ........ Heater Output
Display Brightness ....... 75%
Heater
Heater Range ............... Off
Input Setup – Diode/Resistor Configuration
Input Type .................... Silicon Diode
Curve............................ DT-470
Input Setup – Thermocouple Configuration
Input Type .................... Thermocouple/25mV
Curve............................ Type K
Room Comp ................. On
Room Cal ..................... Cleared
Interface
Baud ............................. 9600
Keypad Locking
Mode .................................... Unlocked
Lock Code ........................... 123
Loop
Selected Loop ...................... Loop 1
Math
Source ................................. Temp K
Linear Equation ................... MX+B
Linear Equation M Value ..... 0.0000
Linear Equation X Source ... Temp K
Linear Equation B Source ... Value
Linear Equation B Value ...... 0.0000
Filter ..................................... Off
PID/Manual Heater Power (MHP) Output
Proportional (P) ................... 50.000
Integral (I) ............................ 20.000
Derivative (D) ....................... 0.0000
MHP Output ......................... 0.0000%
Remote/Local
Remote/Local ...................... Local
Setpoint
Setpoint Value ..................... 0.000K
Tuning
Tuning Mode ........................ Manual PID
Zone Settings – All Zones
Setpoint Limit ....................... 0.000K
Proportional (P) ................... 50.000
Integral (I) ............................ 20.000
Derivative (D) ....................... 0.0000
Manual Output ..................... 0.0000%
IEEE Address ............... 12
IEEE Terminators ......... CR/LF
Emulation Mode ........... 331
4-38 Operation
Page 85
Lake Shore Model 331 Temperature Controller User’s Manual
CHAPTER 5
ADVANCED OPERATION
5.0 GENERAL
This chapter covers the advanced operation of the Model 331 Temperature Controller. Advanced
operation consists of the functions related to temperature response curves. A temperature response
curve can be entered into the Model 331 in several ways: order it factory-installed (Paragraphs 2.2
and 7.2), create a SoftCal curve (Paragraph 5.3); load a curve via the computer interface (refer to the
various curve commands detailed in Paragraph 6.3), or enter a user-generated curve from the front
panel. Advanced functions include details on curve numbers and storage in Paragraph 5.1, front panel
curve entry operations in Paragraph 5.2, and SoftCal™ in Paragraph 5.3.
5.1 CURVE NUMBERS AND STORAGE
The Model 331 has 20 standard curve locations; numbered 1 thru 20. At present, not all locations are
occupied by curves; the others are reserved for future updates. If a standard curve location is in use,
the curve can be viewed using the edit operation. Standard curves can not be changed by the user, and
reserved locations are not available for user curves.
The Model 331 has 20 user curve locations numbered 21 thru 41. Each location can hold from 2 to 200
data pairs (breakpoints) including a value in sensor units and a corresponding value in kelvin. Using
fewer than 200 breakpoints will not increase the number of available curve locations. SoftCal generated
curves are stored in user curve locations.
5.1.1 Curve Header Parameters
Each curve has a set of parameters that are used for identification and to allow the instrument to use
the curve effectively. The parameters must be set correctly before a curve can be used for
temperature conversion or temperature control.
Curve Number: 1 – 41.
Name: Defaults to the name User Curve for front panel entry. When entering a user curve over the
computer interface, a curve name of up to 15 characters can be entered.
Serial Number: Up to a 10-character sensor serial number. Both numbers and letters can be entered
over computer interface, only numbers can be entered from the front panel.
Format: The format parameter tells the instrument what breakpoint data format to expect. Different
sensor types require different formats. Formats for Lake Shore sensors are:
V/K: Volts vs. Kelvin for Diode sensors.
/K: Resistance vs. Kelvin for platinum RTD sensors.
Ω
Log Ω/K: Log Resistance vs. Kelvin for NTC resistive sensors.
Limit: Enter a temperature limit in Kelvin for the curve. Default is 375 K. Enter a setting of 9999 K if
no limit is needed.
Temperature Coefficient: The unit derives the temperature coefficient from the first two breakpoints.
The user does not enter this setting. If it is not correct check for proper entry of those points.
A positive coefficient (
A negative coefficient (
P) indicates that the sensor signal increases with increasing temperature.
N) indicates that the sensor signal decreases with increasing temperature.
Advanced Operation 5-1
Page 86
Lake Shore Model 331 Temperature Controller User’s Manual
5.1.2 Curve Breakpoints
Temperature response data of a calibrated sensor must be reduced to a table of breakpoints before
entering it into the instrument. Each breakpoint consists of one value in sensor units and one
temperature value in kelvin. Linear interpolation is used by the instrument to calculate temperature
between breakpoints. From 2 to 200 breakpoints can be entered as a curve. The instrument will show
an error message on the display if the sensor input is outside the range of the breakpoints. No special
endpoints are required. Sensor units are defined by the format setting in Table 5-2.
Breakpoint setting resolution is six digits in temperature. Most temperature values are entered with
0.001 resolution. Temperature values of 1000 K and greater can be entered to 0.01 resolution.
Temperature values below 10 K can be entered with 0.0001 resolution. Temperature range for curve
entry is 1500 K.
Setting resolution is also six digits in sensor units. The curve format parameter defines the range and
resolution in sensor units as shown in Table 5-2. The sensor type determines the practical setting
resolution. Table 5-2 lists recommended sensor units resolutions. For most sensors, additional
resolution is ignored.
The breakpoints should be entered with the sensor units value increasing as point number increases.
There should not be any breakpoint locations left blank in the middle of a curve. The search routine in
the Model 331 interprets a blank breakpoint as the end of the curve.
5.2 FRONT PANEL CURVE ENTRY OPERATIONS
There are three operations associated with front panel curve entry: Edit curve, Copy curve, Erase
curve; as detailed below.
Edit
Curve
Erase
Curve
Copy
Curve
SoftCal
Edit allows the user to see any curve and enter or edit a curve
at any user curve location. Standard curves cannot be changed.
Erase allows the user to delete a curve from any user curve
location. Standard curves cannot be erased.
Copy allows the user to copy a curve from any location to any
user curve location. Curves cannot be copied into standard
curve locations.
Allows creation of a new temperature curve from a standard
curve and known data points entered by the user.
Refer to
Paragraph 5.2.1
Refer to
Paragraph 5.2.2
Refer to
Paragraph 5.2.3
Refer to
Paragraph 5.3
To begin a curve operation, press the
Curve Entry key and the above selections appear. Press the
Next Setting key until the desired operation is highlighted and press the Enter key. A curve screen
appears with the curve number highlighted. Change to the desired curve number with the up or down
arrow key, then press the
Enter key to begin the desired curve operation.
5-2 Advanced Operation
Page 87
Lake Shore Model 331 Temperature Controller User’s Manual
Table 5-1. Curve Header Parameters
The curve name cannot be changed from the front panel. Curve names can only
Name:
be entered over the computer interface (up to 15 characters). The default curve
name is User xx, where xx is the curve number.
Identify specific sensors with serial numbers of up to 10 characters. The serial
Serial
Num:
number field accepts both numbers and letters, but the instrument front panel
enters only numbers. To enter both numbers and letters, enter curves over
computer interface. The default is blank.
The instrument must know the data format of the curve breakpoints. Different
sensor types use different data formats. The sensor inputs require one of the
formats below. The range and resolution specified are not always available at the
same time. Practical range and resolution depend on the sensor type.
Curve
Format:
Sensor Units Sensor Units
Format Description Full Scale Range Maximum Resolution
V/K Volts vs. Kelvin 10 (V) 0.00001 (V)
Ω/K Resistance vs. Kelvin 10 K (Ω) 0.001 (Ω)
log Ω/K log Resistance vs. Kelvin 4 (log Ω) 0.00001 (log Ω)
mV/K mV vs. Kelvin ±100 (mV) 0.0001 (mV)
SP
Limit
A setpoint temperature limit can be included with every curve. When controlling in
temperature, the setpoint cannot exceed the limit entered with the curve for the
control sensor. The default is 375 K. Set to 9999 K if no limit is required.
The instrument derives the temperature coefficient from the first two breakpoints.
Coeff:
If it is set improperly, check the first two breakpoints. A positive coefficient
indicates the sensor signal increases with increasing temperature. A negative
coefficient indicates the sensor signal decreases with increasing temperature.
Table 5-2. Recommended Curve Parameters
Type
Typical Lake
Shore Model
Units Format
Limit
(K)
Coefficient
Recommended
Sensor Resolution
Silicon Diode DT-470 Volts V/K 475 Negative 0.00001 (V)
GaAlAs Diode TG-120 Volts V/K 325 Negative 0.00001 (V)
Platinum 100 PT-100 Ohms
Platinum 1000 PT-100 Ohms
Rhodium-Iron RF-100 Ohms
Carbon-Glass CGR-1-1000 Ohms
Cernox CX-1030 Ohms
Germanium GR-200A-100 Ohms
Rox RX-102A Ohms
Ω/K
Ω/K
Ω/K
logΩ/K
logΩ/K
logΩ/K
logΩ/K
800 Positive 0.001 (Ω)
800 Positive 0.01 (Ω)
325 Positive 0.001 (Ω)
325 Negative
325 Negative
325 Negative
40 Negative
0.00001 (logΩ)
0.00001 (logΩ)
0.00001 (logΩ)
0.00001 (logΩ)
Type K 9006-005 mV mV/K 1500 Positive 0.0001 (mV)
Type E 9006-003 mV mV/K 930 Positive 0.0001 (mV)
Type T 9006-007 mV mV/K 673 Positive 0.0001 (mV)
Au-Fe 0.03%
No Longer Sold
mV mV/K 500 Positive 0.0001 (mV)
Au-Fe 0.07% 9006-001 mV mV/K 610 Positive 0.0001 (mV)
Advanced Operation 5-3
Page 88
5.2.1 Edit Curve
The Edit Curve operation is used to enter a new curve or edit an existing user curve. Only user
curves (21 to 41) can be changed. Standard curves can only be viewed with the edit operation.
Entering the identification parameters associated with the curve is as important as entering the
breakpoints. Curve header parameters are listed in Table 5-1. Typical parameters for common
sensors are listed in Table 5-2. Read this section completely and gather all necessary data before
beginning the process.
NOTE: If the curve you wish to enter has similar parameters to an existing curve, first
copy the similar curve (as described in Paragraph 5.2.3) to a new location, then
edit the curve to the desired parameters.
To enter a new user curve or edit an existing user curve, press the Curve Entry key. Press the
s or t key until you see the following display.
Lake Shore Model 331 Temperature Controller User’s Manual
Select With °®
Edit Curve
Press the Enter key. Press the Escape key anytime during this routine to return to the normal
display.
Select for Edit °®
Curve 21 User
Use the s or t key to cycle through the various curves. Curve numbers 21 thru 41 are used to copy
or create new curves. You can also view (but not modify) the standard curve numbers 01 thru 20 from
here. For this example, we will enter a new curve in location 21. Press the
Enter key.
Enter for Curve 21
Serial # 0123456789
Use the numerical keypad to enter the applicable sensor serial number; to a maximum of 10 digits.
For this example, we will enter 0123456789. Press the
Enter key.
Select for Curv21 °®
Curve Format V/K
Use the s or t key to cycle through the curve formats: V/K, Ω/K, log Ω/K, mV/K, where V/K = volts
per kelvin, Ω/K = ohms per kelvin, log Ω/K = logarithm of the resistance per kelvin, and mV/K =
millivolts per kelvin. For this example, we will select V/K. Press the
Enter key.
Enter for Curve 21
SP Limit 475.00½
Use the numerical keypad to enter a setpoint limit (in kelvin) appropriate for the sensor being used.
For this example, we will enter 475.00K. Press the
View for Curve 21
Temp Coeff Positive
5-4 Advanced Operation
Enter key.
Page 89
Edit Curve (Continued)
The temperature coefficient (positive or negative) of the curve is displayed. The coefficient is
calculated from the first two points of the curve and cannot be changed. Press the
Now that the curve identification parameters are entered, it is time to enter curve breakpoints.
Lake Shore Model 331 Temperature Controller User’s Manual
Enter key.
User Curve 21
¾ 0.00000v 00.0000½
The cursor initially blinks on the curve breakpoint number. When the cursor is in this position, use the
s or t key to scroll through the breakpoints in the curve. Press the Enter key to modify the current
breakpoint. Use the numerical keypad to enter the applicable sensor value. For this example, we will
enter 0.09062 V, then press the
Enter key. The cursor will jump to the temperature reading. Again
use numerical keypad to enter the applicable temperature in kelvin. For this example, we will enter
475.0 K. Press the
Enter key.
¾ 0.09062v 475.000½
¿ 0.00000v 00.0000½
Use the numerical keypad to enter the remaining voltage and temperature points. After entering the
final point in the curve, press the
display.
To add a new breakpoint to an existing curve, go to the end of the curve data and enter the new
sensor reading and temperature. Press the
automatically put into its proper place in breakpoint sequence.
NOTE: Typing over an existing reading or temperature will replace that value when you
press the
Enter key.
To delete a breakpoint, go to point and enter all zeros for both the sensor reading and temperature.
Press the
Enter key, then the Escape key.
When curve entry is complete, the user must assign the new curve to an input. The Model 331 does
not automatically assign the new curve to either input.
Enter key, then the Escape key. You will return to the normal
Enter key, then the Escape key. The new point is
5.2.1.1 Thermocouple Curve Considerations
The following are things to consider when generating thermocouple curves.
• Users may enter temperature response curves for all types of thermocouples. Enter curve data
in mV/K format with thermocouple voltage in millivolts and temperature in Kelvin.
• The curve must be normalized to 0 mV at 273.15K (0 °C). Thermocouple voltages in millivolts
are positive when temperature is above that point and negative when temperature is below that
point.
• To convert curves published in Celsius to Kelvin, add 273.15 to the temperature in Celsius.
• The temperature range for some thermocouple types may extend below 1 K or above 1000 K.
• The input voltage of the 331 is limited to ±50 mV, so any part of the curve that extends beyond
±50 mV is not usable by the instrument.
• A message of S-OVER or S-UNDER on the display indicates that the measured thermocouple
input is over or under the ±50 mV range.
Advanced Operation 5-5
Page 90
5.2.2 Erase Curve
User curves that are no longer needed may be erased. Erase Curve sets all identification parameters
to default and blanks all breakpoint values.
To erase an existing user curve, press the Curve Entry key. Press the s or t key until you see the
following display.
Lake Shore Model 331 Temperature Controller User’s Manual
Select With °®
Press the Enter key. You can press the Escape key anytime during this routine to return to the
normal display.
Use the s or t key to cycle through the various user curve numbers 21 thru 41. You cannot erase
the standard curve numbers 01 thru 20. Once the user curve number is selected, press the
key. You will see the following message.
Press the Escape key to cancel or the Enter key to erase the selected user curve. You now return to
the normal display.
5.2.3 Copy Curve
Temperature curves can be copied from one location inside the Model 331 to another. This is a good
way to make small changes to an existing curve. Curve copy may also be necessary if the user needs
the same curve with two different temperature limits or needs to extend the range of a standard
curve. The curve that is copied from is always preserved.
NOTE: The copy routine allows you to overwrite an existing user curve. Please ensure
the curve number you are writing to is correct before proceeding with curve copy.
To copy a curve, press the Curve Entry key. Press the s or t key until you see the following
display.
Erase Curve
Select for Erase °®
Curve 21 User
Press Esc. to cancel
or Enter to erase 21
Enter
Select With °®
Copy Curve
Press the Enter key. You can press the Escape key anytime during this routine to return to the
normal display.
Select Copy from °®
Curve 01 DT-470
Use the s or t key to select the curve number (01 thru 41) to copy from.
5-6 Advanced Operation
Page 91
Copy Curve (Continued)
Once the curve number is selected, press the Enter key. You will see the following message.
Lake Shore Model 331 Temperature Controller User’s Manual
Select Copy to °®
Curve 21 User
Use the s or t key to select the curve number (21 thru 41) to copy to. Press the Enter key to copy
the curve. You now return to the normal display.
5.3 SOFTCAL™
The Model 331 allows the user to perform inexpensive sensor calibrations with a set of algorithms
called SoftCal. The two SoftCal algorithms in the Model 331 work with DT-400 Series Silicon Diode
sensors and Platinum Sensors. They create a new temperature response curve from the standard
curve and known data points entered by the user. The new curve loads into one of the user curve
locations (21 thru 41) in the instrument. The following paragraphs describe the data points needed from
the user and the expected accuracy of the resulting curves.
Both DT-400 Series and Platinum SoftCal algorithms require a standard curve that is already present in
the Model 331. When the user enters the type of sensor being calibrated, the correct standard curve
must be selected. When calibration is complete, the user must assign the new curve to an input. The
Model 331 does not automatically assign the newly generated curve to either input.
Calibration data points must be entered into the Model 331. These calibration points are normally
measured at easily obtained temperatures like the boiling point of cryogens. Each algorithm operates
with one, two, or three calibration points. The range of improved accuracy increases with more points.
There are two ways to get SoftCal calibration data points: The user can record the response of an
unknown sensor at well controlled temperatures, or
sensor from Lake Shore. There are advantages to both methods.
The user can purchase a SoftCal calibrated
User: When the user can provide stable calibration temperatures with the sensor installed, SoftCal
calibration eliminates errors in the sensor measurement as well as the sensor. Thermal gradients,
instrument accuracy, and other measurement errors can be significant to some users. Calibration
can be no better than user-supplied data.
Purchased: Lake Shore sensors with SoftCal calibration include a set of calibration points in the
calibration report. The SoftCal calibration points are generated in a controlled calibration facility at
Lake Shore for best accuracy. The calibration points can be entered into the Model 331 so it can
generate a curve. If the CalCurve service is purchased with the calibrated sensor, the curve is also
generated at the factory and can be entered like any other curve.
5.3.1 SoftCal With Silicon Diode Sensors
Lake Shore Silicon Diode Sensors incorporate remarkably uniform sensing elements that exhibit
precise, monotonic, and repeatable temperature response. For example, the Lake Shore DT-470
Series of silicon diode sensors has a repeatable temperature response from 2 K to 475 K. These
sensors closely follow the Standard Curve 10 response and routinely interchange with one another.
SoftCal is an inexpensive way to improve the accuracy of an already predictable sensor.
NOTE: Standard Curve 10 is the name of the temperature response curve, not its location inside the
Model 331. Standard Curve 10 is stored in Curve Location Number 1 in the Model 331.
A unique characteristic of DT-400 Series diodes is that their temperature responses pass through
28 K at almost exactly the same voltage. This improves SoftCal algorithm operation by providing an
extra calibration data point. It also explains why SoftCal calibration specifications are divided into two
temperature ranges, above and below 28 K. See Figure 5-1.
Advanced Operation 5-7
Page 92
SoftCal Point 1SoftCal Point 1
Liquid Helium
Boiling Point
4.2 K
0 25 50 75 100 125 150 175 200 225 250 275 300 325 350
Lake Shore Model 331 Temperature Controller User’s Manual
SoftCal Point 2
Liquid Nitrogen
SoftCal Point 1
Room Temperature
Boiling Point
77.35 K
Point
305 K
2 10 K 50 100 K 200 325 K
Acceptable Temperature Range for Silicon Diode SoftCal Inputs
C-331-5-1.eps
Figure 5-1. SoftCal Temperature Ranges for Silicon Diode Sensors
Point 1: Calibration data point at or near the boiling point of helium, 4.2 K. Temperatures
outside 2 K to 10 K are not allowed. This data point improves between the calibration
data point and 28K. Points 2 and 3 improve temperatures above 28 K.
Point 2: Calibration data point at or near the boiling point of nitrogen (77.35 K). Temperatures
outside 50 K to 100 K are not allowed. This data point improves accuracy between 28
K and 100 K. Points 2 and 3, together, improve accuracy to room temperature and
above.
Point 3: Calibration data point near room temperature (305 K). Temperatures outside the range
of 200 K to 350 K are not allowed.
5.3.2 SoftCal Accuracy With Silicon Diode Sensors
A SoftCal calibration is only as good as the accuracy of the calibration points. The accuracies listed
for SoftCal assume ±0.01 K for 4.2 K (liquid helium), ±0.05 K for 77.35 K (liquid nitrogen), and 305 K
(room temperature) points. Users performing the SoftCal with Lake Shore instruments should note
that the boiling point of liquid cryogen, though accurate, is affected by atmospheric pressure.
Use calibrated standard sensors if possible.
One-point SoftCal calibrations for applications under 30 K are performed at liquid helium (4.2 K)
temperature. Accuracy for the DT-470-SD-13 diode is ±0.5 K from 2 K to <30 K with no accuracy
change above 30 K.
Two-point SoftCal calibrations for applications above 30 K are performed at liquid nitrogen (77.35 K)
and room temperature (305 K). Accuracy for the DT-470-SD-13 diode sensor is as follows:
±1.0 K 2 K to <30 K (no change below 30 K)
±0.25 K 30 K to <60 K
±0.15 K 60 K to <345 K
±0.25 K 345 K to <375 K
±1.0 K 375 to 475 K
Three-point SoftCal calibrations are performed at liquid helium (4.2 K), liquid nitrogen (77.35 K), and
room temperature (305 K). Accuracy for the DT-470-SD-13 diode sensor is as follows:
±0.5 K 2 K to <30
±0.25 K 30 K to <60 K
±0.15 K 60 K to <345 K
±0.25 K 345 K to <375 K
±1.0 K 375 to 475 K
5-8 Advanced Operation
Page 93
Lake Shore Model 331 Temperature Controller User’s Manual
5.3.3 SoftCal With Platinum Sensors
The platinum sensor is a well-accepted temperature standard because of its consistent and
repeatable temperature response above 30 K. SoftCal gives platinum sensors better accuracy than
their nominal matching to the DIN 43760 curve.
SoftCal Point 1SoftCal Point 1
Liquid Nitrogen
Boiling Point
77.35 K
SoftCal Point 2
Room Temperature
Point
305 K
SoftCal Point 3
High Temperature
Point
480 K
0 50 100 150 200 250 300 350
Acceptable Temperature Range for Platinum SoftCal Inputs
C-331-5-2.eps
Figure 5-2. SoftCal Temperature Ranges for Platinum Sensors
One, two, or three calibration data points can be used. If using one point, the algorithm shifts the
entire curve up or down to meet the single point. If using two points, the algorithm has enough
information to tilt the curve, achieving good accuracy between the data points. The third point extends
the improved accuracy to span all three points.
Point 1: Calibration data point at or near the boiling point of nitrogen (77.35 K). Temperatures
outside 50 K to 100 K are not allowed.
Point 2: Calibration data point near room temperature (305 K). Temperatures outside 200 K to
350 K are not allowed.
Point 3: Calibration data point at a higher temperature (480 K). Temperatures outside 400 K to
600 K are not allowed.
5.3.4 SoftCal Accuracy With Platinum Sensors
A SoftCal calibration is only as good as the accuracy of the calibration points. The accuracies listed
for SoftCal assume ±0.05 K for 77.35 K (liquid nitrogen) and 305 K (room temperature) points. Users
performing the SoftCal with Lake Shore instruments should note that the boiling point of liquid
cryogen, though accurate, is affected by atmospheric pressure. Use calibrated standard sensors if
possible.
One-point SoftCal calibrations with platinum sensors have no specified accuracy.
Two-point SoftCal calibrations for applications above 70 K are performed at liquid nitrogen (77.35 K)
and room temperature (305 K). Accuracy for the PT-102, PT-103, or PT-111 platinum sensor is as
follows:
±250 mK from 70 K to 325 K
≈±500 mK from 325 K to ≈±1400 mK at 480 K
(DIN Class A or Class B tolerance)
Three-point SoftCal calibrations are performed at liquid nitrogen (77.35 K), room temperature (305 K),
and high temperature (480 K). Accuracy for the PT-102, PT-103, or PT-111 platinum sensor is
mK from 70 K to 325 K, and ±250 mK from 325 K to 480 K.
400 450 500 550 600 650
400 600 K50 100 K 200 325 K
±250
Advanced Operation 5-9
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Lake Shore Model 331 Temperature Controller User’s Manual
5.3.5 SoftCal Calibration Curve Creation
Once the calibration data points have been obtained, you may create a SoftCal calibration. This
example illustrates SoftCal of a DT-470 Diode. Press the
until you see the following display.
Select With °®
Curve Entry key. Press the s or t key
SoftCal
Press the Enter key. You can press the Escape key anytime during this routine to return to the
normal display.
Select for Scal °®
DT-470
Use the s or t key to cycle through the sensor type you wish to SoftCal: DT-470, PT-100, and
PT-1000. Once the sensor type is selected, press the
Enter key. You will see the following message.
Select Write to °®
Curve 21 User
NOTE: The copy routine allows you to overwrite an existing user curve. Please ensure the
Use the s or t key to select the user curve location where the SoftCal curve will be stored. You can
choose any of the user curve locations, 21 thru 41. Press the
message.
curve number you are writing to is correct before proceeding with curve copy.
Enter key. You will see the following
Serial #
0123456789
Use the numerical keypad to enter the applicable sensor serial number; to a maximum of 10 digits.
For this example, we will enter 0123456789. Press the
Enter key.
Point 1
+1.62999v 04.1800½
NOTE: If Point 1 is not being used, press the Enter key with both settings at their default
value and advance to Point 2.
Use the numerical keypad to enter the measured data point at or near the boiling point of helium
(4.2 K). Temperatures outside the range of 2
Please Reenter” is displayed if either point is outside the acceptable range. For this example, we will
enter 1.62999. Press the
Enter key. The cursor will jump to the temperature reading. Again use
numerical keypad to enter the temperature the measurement was taken at. For this example, we will
enter 4.18 K. Press the
Enter key.
Point 2
+1.02111v 77.0000½
5-10 Advanced Operation
– 10 K are not permitted. The message “Invalid Point.
Page 95
SoftCal Calibration Curve Creation (Continued)
Lake Shore Model 331 Temperature Controller User’s Manual
NOTE: If Point 2 is not being used, press the Enter key with both settings at their default
value and advance to Point 3.
Use the numerical keypad to enter the measured data point at or near the boiling point of nitrogen
(77.35 K). Temperatures outside the range of 50
enter 1.02111. Press the
Enter key. The cursor will jump to the temperature reading. Again use
numerical keypad to enter the temperature the measurement was taken at. For this example, we will
enter 77 K. Press the
Enter key.
Point 3
– 100 K are not permitted. For this example, we will
+0.51583v 302.500½
NOTE: If Point 3 is not being used, press the Enter key with both settings at their default
value to complete the SoftCal calibration.
Use the numerical keypad to enter the measured data point at or near room temperature (305 K).
Temperatures outside the range of 200
0.51583. Press the
Enter key. The cursor will jump to the temperature reading. Again use numerical
– 350 K are not permitted. For this example, we will enter
keypad to enter the temperature the measurement was taken at. For this example, we will enter
302.5 K. Press the
Enter key.
The new curve is automatically generated and you will return to the normal display. You can check
the new curve using the Edit Curve instructions in Paragraph 5.2.1. The curve is not automatically
assigned to either input, so the new curve must be assigned to an input by the user.
Advanced Operation 5-11
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Lake Shore Model 331 Temperature Controller User’s Manual
This Page Intentionally Left Blank
5-12 Advanced Operation
Page 97
Lake Shore Model 331 Temperature Controller User’s Manual
CHAPTER 6
COMPUTER INTERFACE OPERATION
6.0 GENERAL
This chapter provides operational instructions for the computer interface for the Lake Shore Model 331
Temperature Controller. Either of the two computer interfaces provided with the Model 331 permit
remote operation. The first is the IEEE-488 Interface described in Paragraph 6.1. The second is the
Serial Interface described in Paragraph 6.2. The two interfaces share a common set of commands
detailed in Paragraph 6.3. Only one of the interfaces can be used at a time.
NOTE: The remote interface of the Model 331 can be set to emulate a Lake Shore Model 330
Temperature Controller. Refer to Paragraph 4.20 to select 330 Emulation Mode. Refer
to your Model 330 User’s Manual for command syntax. The following Model 330
commands are not supported in 330 Emulation Mode: CUID?, CURV, CURV?, ECUR,
KCUR, and SCAL.
6.1 IEEE-488 INTERFACE (Model 331S Only)
The IEEE-488 Interface is an instrumentation bus with hardware and programming standards that
simplify instrument interfacing. The Model 331 IEEE-488 Interface complies with the IEEE-488.2-1987
standard and incorporates its functional, electrical, and mechanical specifications unless otherwise
specified in this manual.
All instruments on the interface bus perform one or more of the interface functions of TALKER,
LISTENER, or BUS CONTROLLER. A TALKER transmits data onto the bus to other devices. A
LISTENER receives data from other devices through the bus. The BUS CONTROLLER designates to
the devices on the bus which function to perform. The Model 331 performs the functions of TALKER
and LISTENER but cannot be a BUS CONTROLLER. The BUS CONTROLLER is the digital computer
which tells the Model 331 which functions to perform.
Below are Model 331 IEEE-488 interface capabilities:
SH1: Source handshake capability.
•
•
RL1: Complete remote/local capability.
•
DC1: Full device clear capability.
•
DT0: No device trigger capability.
•
C0: No system controller capability.
•
T5: Basic TALKER, serial poll capability, talk only, unaddressed to talk if addressed to listen.
•
L4: Basic LISTENER, unaddressed to listen if addressed to talk.
•
SR1: Service request capability.
•
AH1: Acceptor handshake capability.
•
PP0: No parallel poll capability.
•
E1: Open collector electronics.
NOTE: The Model 331 IEEE-488 Interface requires that repeat addressing be enabled
Instruments are connected to the IEEE-488 bus by a 24-conductor connector cable as specified by the
standard. Refer to Paragraph 8.4.2. Cables can be purchased from Lake Shore or other electronic
suppliers. A connector extender (Model 4005) is required to use the IEEE-488 Interface and the RELAY
and ANALOG OUTPUT Terminal Block at the same time.
Cable lengths are limited to 2 meters for each device and 20 meters for the entire bus. The Model 331
can drive a bus with up to 10 loads. If more instruments or cable length is required, a bus expander
must be used.
on the bus controller.
Remote Operation 6-1
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Lake Shore Model 331 Temperature Controller User’s Manual
6.1.1 Changing IEEE-488 Interface Parameters
Two interface parameters, address and terminators, must be set from the front panel before
communication with the instrument can be established. Other interface parameters can be set with
device specific commands using the interface (Paragraph 6.3).
Press the Interface key. The first screen is for selecting the Serial Interface Baud Rate, and can be
skipped by pressing the
Enter key. The Address screen is then displayed as follows.
Select−With−°®
Press the s or t keys to increment or decrement the IEEE Address to the desired number. Valid
addresses are 1 thru 30. Default is 12. Press
existing number. Pressing
Enter displays the Terminators screen.
Press the s or t keys to cycle through the following Terminator choices: CR/LF, LF/CR, LF, and
EOI. The default is Cr Lf. To accept changes or the currently displayed setting, push
changes, push
Escape.
6.1.2 IEEE-488 Command Structure
The Model 331 supports several command types. These commands are divided into three groups.
Bus Control – Refer to Paragraph 6.1.2.1.
1.
a. Universal
(1) Uniline
(2) Multiline
b. Addressed Bus Control
2.
Common – Refer to Paragraph 6.1.2.2.
Device Specific – Refer to Paragraph 6.1.2.3.
3.
Message Strings – Refer to Paragraph 6.1.2.4.
4.
IEEE−Address−−12
Enter to accept new number or Escape to retain the
Select−With−°®
IEEE Term−−Cr−Lf
Enter. To cancel
6.1.2.1 Bus Control Commands
A Universal Command addresses all devices on the bus. Universal Commands include Uniline and
Multiline Commands. A Uniline Command (Message) asserts only a single signal line. The Model
331 recognizes two of these messages from the BUS CONTROLLER:
Interface Clear (IFC). The Model 331 sends one Uniline Command: Service Request (SRQ).
REN (Remote) – Puts the Model 331 into remote mode.
IFC (Interface Clear) – Stops current operation on the bus.
SRQ (Service Request) – Tells the bus controller that the Model 331 needs interface service.
A Multiline Command asserts a group of signal lines. All devices equipped to implement such
commands do so simultaneously upon command transmission. These commands transmit with the
Attention (ATN) line asserted low. The Model 331 recognizes two Multiline commands:
LLO (Local Lockout) – Prevents the use of instrument front panel controls.
DCL (Device Clear) – Clears Model 331 interface activity and puts it into a bus idle state.
6-2 Remote Operation
Remote (REN) and
Page 99
Bus Control Commands (Continued)
Lake Shore Model 331 Temperature Controller User’s Manual
Finally, Addressed Bus Control Commands are Multiline commands that must include the Model
331 listen address before the instrument responds. Only the addressed device responds to these
commands. The Model 331 recognizes three of the Addressed Bus Control Commands:
SDC (Selective Device Clear) – The SDC command performs essentially the same function as the
DCL command except that only the addressed device responds.
GTL (Go To Local) – The GTL command is used to remove instruments from the remote mode.
With some instruments, GTL also unlocks front panel controls if they were previously locked out
with the LLO command.
SPE (Serial Poll Enable) and SPD (Serial Poll Disable) – Serial polling accesses the Service
Request Status Byte Register. This status register contains important operational information
from the unit requesting service. The SPD command ends the polling sequence.
6.1.2.2 Common Commands
Common Commands are addressed commands which create commonalty between instruments on
the bus. All instruments that comply with the IEEE-488 1987 standard share these commands and
their format. Common commands all begin with an asterisk. They generally relate to “bus” and
“instrument” status and identification. Common query commands end with a question mark (?).
Model 331 common commands are detailed in Paragraph 6.3 and summarized in Table 6-8.
6.1.2.3 Device Specific Commands
Device specific commands are addressed commands. The Model 331 supports a variety of device
specific commands to program instruments remotely from a digital computer and to transfer
measurements to the computer. Most device specific commands perform functions also performed
from the front panel. Model 331 device specific commands are detailed in Paragraph 6.3 and
summarized in Table 6-8.
6.1.2.4 Message Strings
A message string is a group of characters assembled to perform an interface function. There are
three types of message strings commands, queries and responses. The computer issues command
and query strings through user programs, the instrument issues responses. Two or more command
strings can be chained together in one communication but they must be separated by a semi-colon
(;). Only one query is permitted per communication but it can be chained to the end of a command.
The total communication string must not exceed 64 characters in length.
A command string is issued by the computer and instructs the instrument to perform a function or
change a parameter setting. When a command is issued, the computer is acting as ‘talker’ and the
instrument as ‘listener’. The format is:
<command mnemonic><space><parameter data><terminators>.
Command mnemonics and parameter data necessary for each one is described in Paragraph 6.3.
Terminators must be sent with every message string.
A query string is issued by the computer and instructs the instrument which response to send.
Queries are issued similar to commands with the computer acting as 'talker' and the instrument as
'listener'. The query format is:
<query mnemonic><?><space><parameter data><terminators>.
Query mnemonics are often the same as commands with the addition of a question mark.
Parameter data is often unnecessary when sending queries. Query mnemonics and parameter data
if necessary is described in Paragraph 6.3. Terminators must be sent with every message string.
Issuing a query does not initiate a response from the instrument.
A response string is sent by the instrument only when it is addressed as a 'talker' and the computer
becomes the 'listener'. The instrument will respond only to the last query it receives. The response
can be a reading value, status report or the present value of a parameter. Response data formats
are listed along with the associated queries in Paragraph 6.3.
Remote Operation 6-3
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Lake Shore Model 331 Temperature Controller User’s Manual
6.1.3 Status Registers
There are two status registers: the Status Byte Register described in Paragraph 6.1.3.1, and the
Standard Event Status Register in Paragraph 6.1.3.2.
6.1.3.1 Status Byte Register and Service Request Enable Register
The Status Byte Register contains six bits of information about the operation of the Model 331.
STATUS BYTE REGISTER FORMAT
Bit – 7 6 5 4 3 2 1 0
Weighting – 128 64 32 16 8 4 2 1
Bit Name –
Ramp
Done
SRQ ESB Error Alarm
If Service Request is enabled, any of these bits being set will cause the Model 331 to pull the SRQ
management line low to signal the BUS CONTROLLER. These bits are reset to zero upon a serial
poll of the Status Byte Register. These reports can be inhibited by turning their corresponding bits
in the Service Request Enable Register to off.
The Service Request Enable Register allows the user to inhibit or enable any of the status reports
in the Status Byte Register. The
QSRE command is used to set the bits. If a bit in the Service
Request Enable Register is set (1), then that function is enabled. Refer to the
discussion.
Ramp Done, Bit (7) – This bit is set when the ramp is completed.
Service Request (SRQ) Bit (6) – Determines whether the Model 331 is to report via the SRQ line.
If bits 0, 3, 4, 5 and/or 7 are set, then the corresponding bit in the Status Byte Register will be set.
The Model 331 will produce a service request only if bit 6 of the Service Request Enable Register
is set. If disabled, the Status Byte Register can still be read by the BUS CONTROLLER by means
of a serial poll (SPE) to examine the status reports, but the BUS CONTROLLER will not be
interrupted by the Service Request. The
Register but will not clear the bits.
QSTB common command will read the Status Byte
Standard Event Status (ESB), Bit (5) – When bit 5 is set, it indicates if one of the bits from the
Standard Event Status Register has been set. (Refer to Paragraph 6.1.3.2.)
Error, Bit (4) – This bit is set when there is an instrument error not related to the bus.
Alarm, Bit (3) – This bit is set when there is an alarm condition.
New A&B, Bit (0) – This bit is set when new data is available from the normal inputs.
Not
Used
Not
Used
QSRE command
New
A&B
6.1.3.2 Standard Event Status Register and Standard Event Status Enable Register
The Standard Event Status Register reports IEEE bus status of the Model 331.
Bit – 7 6 5 4 3 2 1 0
Weighting – 128 64 32 16 8 4 2 1
Bit Name – PON
Bits 2 and 6 are not used. The bus controller will only be interrupted with the reports of this register
if the bits have been enabled in the Standard Event Status Enable Register and if bit 5 of the
Service Request Enable Register has been set.
The Standard Event Status Enable Register allows the user to enable any of the Standard Event
Status Register reports. The Standard Event Status Enable command (
Event Status Enable Register bits. If a bit of this register is set, then that function is enabled. To set
a bit, send the command
together. See the
6-4 Remote Operation
QESE command discussion for further details.
STANDARD EVENT STATUS REGISTER FORMAT
Not Used
CME EXE DDE QYE
Not Used
OPC
QESE) sets the Standard
QESE with the bit weighting for each bit you want to be set added
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