Lake Shore Model 421 User Manual

User’s Manual

Model 421

Gaussmeter

Lake Shore Cryotronics, Inc. 575 McCorkle Boulevard Westerville, Ohio 43082-8888 USA

E-Mail Addresses:

sales@lakeshore.com service@lakeshore.com

Visit Our Website:

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.

Rev. 1.5 P/N 119-030 18 March 2004

Lake Shore Model 421 Gaussmeter User’s Manual

LIMITED WARRANTY STATEMENT

WARRANTY PERIOD: ONE (1) YEAR

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 (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 421 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 421 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 421 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 ™

symbol.

CalCurve™, Carbon-Glass™, Cernox™, Duo-Twist™,

High-Temperature Cernox™, Quad-Lead™, Quad-Twist™, Rox™, SoftCal™, and Thermox™ 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 © 1999, 2000, 2003, and 2004 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.

Lake Shore Model 421 Gaussmeter 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: .............. EN 61010-1:2001

Overvoltage II Pollution Degree 2

EN 61326 A2:2001

Class A Annex B

Model Number:.......................................................... 421

Ed Maloof

Printed Name

Vice President of Engineering

Position

Lake Shore Model 421 Gaussmeter User’s Manual

Electromagnetic Compatibility (EMC) for the Model 421 Gaussmeter

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 421 meets or exceeds the generic 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.

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 421 should consider the following:

• Leave no unused or unterminated cables attached to the instrument.

• Make cable runs as short and direct as possible.

• Do not tightly bundle cables that carry different types of signals.

adequate measures.

Lake Shore Model 421 Gaussmeter User’s Manual

TABLE OF CONTENTS

Chapter/Paragraph Title Page

1 INTRODUCTION .................................................................................................................................... 1-1

1.0 GENERAL ........................................................................................................................... 1-1

1.1 PRODUCT DESCRIPTION................................................................................................. 1-1

1.2 SPECIFICATIONS ..............................................................................................................1-3

1.3 SAFETY SUMMARY........................................................................................................... 1-4

1.4 SAFETY SYMBOLS............................................................................................................ 1-4

2 INSTALLATION ..................................................................................................................................... 2-1

2.0 GENERAL ........................................................................................................................... 2-1

2.1 INSPECTION AND UNPACKING ....................................................................................... 2-1

2.2 REPACKAGING FOR SHIPMENT .....................................................................................2-1

2.3 REAR PANEL DEFINITION................................................................................................ 2-2

2.4 LINE INPUT ASSEMBLY.................................................................................................... 2-3

2.4.1 Line Voltage and Fuse Verification.................................................................................. 2-3

2.4.2 Power Cord...................................................................................................................... 2-3

2.4.3 Power Switch ................................................................................................................... 2-3

2.5 PROBE INPUT CONNECTION .......................................................................................... 2-3

2.5.1 Attachment To A Hall Generator...................................................................................... 2-4

2.6 CORRECTED AND MONITOR ANALOG OUTPUTS ........................................................ 2-4

2.7 RELAY TERMINAL BLOCK................................................................................................ 2-4

2.8 INITIAL SETUP AND SYSTEM CHECKOUT PROCEDURE............................................. 2-5

3 OPERATION .......................................................................................................................................... 3-1

3.0 GENERAL ........................................................................................................................... 3-1

3.1 DEFINITION OF FRONT PANEL CONTROLS .................................................................. 3-1

3.1.1 Front Panel Keypad ......................................................................................................... 3-1

3.1.2 Front Panel Display ......................................................................................................... 3-2

3.1.3 General Keypad Operation .............................................................................................. 3-3

3.2 GAUSS/TESLA ................................................................................................................... 3-3

3.3 AC/DC ................................................................................................................................. 3-4

3.4 DISPLAY FILTER................................................................................................................ 3-4

3.5 MANUAL RANGE AND AUTO RANGE.............................................................................. 3-5

3.6 ZERO PROBE..................................................................................................................... 3-6

3.7 MAX HOLD AND MAX RESET........................................................................................... 3-6

3.8 RELATIVE........................................................................................................................... 3-7

3.9 ALARM AND RELAY ..........................................................................................................3-7

3.10 ANALOG OUTPUTS......................................................................................................... 3-10

3.11 INTERFACE PARAMETERS............................................................................................ 3-11

3.12 FAST DATA MODE........................................................................................................... 3-11

3.13 LOCKING AND UNLOCKING THE KEYPAD................................................................... 3-12

3.14 DISPLAY BRIGHTNESS .................................................................................................. 3-12

3.15 FACTORY DEFAULT SETTINGS .................................................................................... 3-12

3.16 PROBE CONSIDERATIONS ............................................................................................ 3-13

3.16.1 Changing Probes ........................................................................................................... 3-13

3.16.2 Probe Handling .............................................................................................................. 3-13

3.16.3 Probe Operation ............................................................................................................ 3-14

3.16.4 Probe Accuracy Considerations ....................................................................................3-15

Lake Shore Model 421 Gaussmeter User’s Manual

Chapter/Paragraph Title Page

TABLE OF CONTENTS (Continued)

4 REMOTE OPERATION ..........................................................................................................................4-1

4.0 GENERAL............................................................................................................................4-1

4.1 SERIAL INTERFACE OVERVIEW......................................................................................4-1

4.1.1 Physical Connection.........................................................................................................4-1

4.1.2 Hardware Support ............................................................................................................4-2

4.1.3 Character Format .............................................................................................................4-2

4.1.4 Message Strings...............................................................................................................4-2

4.1.5 Message Flow Control......................................................................................................4-3

4.1.6 Changing Baud Rate........................................................................................................4-3

4.1.7 Serial Interface Basic Programs.......................................................................................4-4

4.1.8 Troubleshooting................................................................................................................4-9

4.2 SERIAL INTERFACE COMMAND SUMMARY...................................................................4-9

4.2.1 Interface Commands ......................................................................................................4-11

4.2.2 Device Specific Commands ...........................................................................................4-12

5 ACCESSORIES AND PROBES.............................................................................................................5-1

5.0 GENERAL............................................................................................................................5-1

5.1 ACCESSORIES...................................................................................................................5-1

5.2 LAKE SHORE STANDARD PROBES.................................................................................5-3

5.2.1 Probe Selection Criteria ...................................................................................................5-3

5.2.2 Radiation Effect on Gaussmeter Probes..........................................................................5-3

5.2.3 Probe Specifications.........................................................................................................5-4

5.3 HELMHOLTZ COIL LOW FIELD STANDARDS..................................................................5-8

5.4 REFERENCE MAGNETS..................................................................................................5-10

6 SERVICE.................................................................................................................................................6-1

6.0 GENERAL............................................................................................................................6-1

6.1 GENERAL MAINTENANCE PRECAUTIONS .....................................................................6-1

6.2 ELECTROSTATIC DISCHARGE ........................................................................................6-1

6.2.1 Identification of Electrostatic Discharge Sensitive Components......................................6-2

6.2.2 Handling Electrostatic Discharge Sensitive Components ................................................6-2

6.3 LINE VOLTAGE SELECTION .............................................................................................6-2

6.4 FUSE REPLACEMENT .......................................................................................................6-3

6.5 REAR PANEL CONNECTOR DEFINITIONS......................................................................6-4

6.5.1 Serial Interface Cable Wiring ...........................................................................................6-6

6.6 TOP OF ENCLOSURE REMOVAL AND REPLACEMENT ................................................6-7

6.6.1 Removal Procedure..........................................................................................................6-7

6.6.2 Installation Procedure.......................................................................................................6-7

6.7 EPROM REPLACEMENT ...................................................................................................6-7

6.8 ERROR MESSAGES ..........................................................................................................6-8

APPENDIX A – GLOSSARY OF TERMINOLOGY .....................................................................................A-1

APPENDIX B – UNITS FOR MAGNETIC PROPERTIES............................................................................ B-1

APPENDIX C – HALL GENERATORS........................................................................................................ C-1

C1.0 GENERAL........................................................................................................................... C-1

C2.0 THEORY OF OPERATION ................................................................................................C-1

C2.1 Active Area ......................................................................................................................C-1

C2.2 Orientation....................................................................................................................... C-2

C2.3 Handling .......................................................................................................................... C-3

C2.4 Polarity............................................................................................................................. C-3

C2.5 Lead Configurations ........................................................................................................C-3

C3.0 HALL GENERATOR GENERIC HOOKUP......................................................................... C-3

C4.0 USING A HALL GENERATOR WITH THE MODEL 421 ...................................................C-4

C5.0 SPECIFICATIONS.............................................................................................................. C-5

C6.0 HALLCAL.EXE PROGRAM................................................................................................ C-8

Lake Shore Model 421 Gaussmeter User’s Manual

LIST OF ILLUSTRATIONS

Figure No. Title Page

1-1 Model 421 Gaussmeter Front Panel............................................................................................. 1-1

2-1 Model 421 Rear Panel .................................................................................................................. 2-2

2-2 Line Input Assembly ..................................................................................................................... 2-3

2-3 Model MCBL-XX User Programmable Cable Assembly............................................................... 2-4

3-1 Model 421 Front Panel ................................................................................................................. 3-1

3-2 Front Panel Display Definition ...................................................................................................... 3-2

3-3 Model 421 AC Frequency Response............................................................................................ 3-4

3-4 Maximum Flexible Probe Bend Radius....................................................................................... 3-14

3-5 Probe Orientation For Positive Measurement ............................................................................ 3-14

3-6 Effect Of Angle On Measurements ............................................................................................. 3-15

5-1 Definition of Lake Shore Gamma Probe....................................................................................... 5-4

5-2 Definition of Lake Shore Robust (Brass Stem) Transverse Probes ............................................. 5-4

5-3 Definition of Lake Shore Transverse Probes................................................................................ 5-5

5-4 Definition of Lake Shore Tangential Probe...................................................................................5-5

5-5 Definition of Lake Shore Axial Probes .......................................................................................... 5-6

5-6 Definition of Lake Shore Flexible Transverse Probes .................................................................. 5-7

5-7 Definition of Lake Shore Flexible Axial Probe .............................................................................. 5-7

5-8 Model MH-2.5 Helmholtz Coil ....................................................................................................... 5-8

5-9 Model MH-6 Helmholtz Coil .......................................................................................................... 5-9

5-10 Model MH-12 Helmholtz Coil ........................................................................................................ 5-9

5-11 Lake Shore Reference Magnets ................................................................................................. 5-10

5-12 Model 4060 Standard Zero Gauss Chamber.............................................................................. 5-11

5-13 Model 4065 Large Zero Gauss Chamber ................................................................................... 5-11

5-14 Model RM-1/2 Rack-Mount Kit.................................................................................................... 5-12

5-15 Model RM-2 Dual Rack-Mount Shelf .......................................................................................... 5-13

6-1 Power Fuse Access ...................................................................................................................... 6-3

6-2 PROBE INPUT Connector Details................................................................................................ 6-4

6-3 Corrected and Monitor ANALOG OUTPUTS Connector Details.................................................. 6-4

6-4 RELAY Terminal Block Details ..................................................................................................... 6-5

6-5 SERIAL I/O (DTE) Connector Details........................................................................................... 6-5

6-6 Location Of Operating Software EPROM and Analog Output Jumper......................................... 6-8

C-1 Hall Generator Theory ..................................................................................................................C-2

C-2 Axial and Transverse Configurations............................................................................................C-2

C-3 Typical Hall Generator Hookup.....................................................................................................C-4

C-4 Hall Generator Input Impedance...................................................................................................C-4

C-5 Axial Hall Generator HGA-3010, HGA-3030, & HGCA-3020 Dimensions ...................................C-5

C-6 Transverse Hall Generator HGT-3010, HGT-3030, & HGCT-3020 Dimensions..........................C-5

C-7 Transverse Hall Generator HGT-1010 Dimensions......................................................................C-6

iii

Lake Shore Model 421 Gaussmeter User’s Manual

LIST OF TABLES

Table No. Title Page

4-1 Serial Interface Specifications .......................................................................................................4-2

4-2 Serial Interface Program Control Properties .................................................................................4-5

4-3 Visual Basic Serial Interface Program...........................................................................................4-6

4-4 Quick Basic Serial Interface Program ...........................................................................................4-7

4-5 Serial Interface Commands.........................................................................................................4-10

B-1 Conversion from CGS to SI Units ................................................................................................ B-1

B-2 Recommended SI Values for Physical Constants........................................................................ B-2

C-1 Cryogenic Hall Generator Specifications .....................................................................................C-5

C-2 Axial Hall Generator Specifications.............................................................................................. C-6

C-3 Transverse Hall Generator Specifications....................................................................................C-7

Lake Shore Model 421 Gaussmeter User’s Manual

CHAPTER 1

INTRODUCTION

1.0 GENERAL

This chapter provides an introduction to the Lake Shore Model 421 Gaussmeter. The Model 421 was designed and manufactured in the United States of America by Lake Shore Cryotronics, Inc. The Model 421 is a highly accurate gaussmeter well suited for field work. It features:

• Resolution to 4¾ Digits.

• Large Vacuum Fluorescent Display.

• Serial Interface.

• Analog Voltage Outputs.

• Max Hold and Relative Reading.

• Alarm with Relay.

If you have just received your new Model 421, please proceed to Chapter 2 and become familiar with the installation instructions. Complete and detailed instrument and probe operational information is contained in Chapter 3. Chapter 4 contains details on remote operation using the Serial Interface. Details on accessories and probes are provided in Chapter 5. Limited service and rear panel connector definitions are contained in Chapter 6. Appendix A is a glossary of terminology. Appendix B provides units for magnetic properties. Finally, Appendix C provides information on Hall sensors and the Hallcal.exe program.

1.1 PRODUCT DESCRIPTION

The Model 421 Hall Effect Gaussmeter is the Lake Shore answer to the dynamic changes in the permanent magnet industry. Faster, higher resolution, and more repeatable flux density measurements are being demanded by manufacturing, quality assurance (QA), and research and development (R&D). The Model 421 is well suited to meet these requirements at an affordable price. The Model 421 is compatible with the extensive Lake Shore line of probes, or we can design custom probes to meet your unique needs. As an added advantage, the Model 421 is provided with one probe of customer choice.

421_Front.bmp

Introduction 1-1

Figure 1-1. Model 421 Gaussmeter Front Panel

Product Description (Continued)

Lake Shore Model 421 Gaussmeter User’s Manual

Performance

High-performance instrumentation is no longer the exclusive domain of research laboratories. Performance requirements are tightening in every magnetic measurement application. In response, the Model 421 offers improved accuracy, resolution, noise floor, and update rate.

Throughput

Throughput involves much more than update rate of an instrument. Usability of an instrument is just as important. The Model 421 has a large, bright, vacuum fluorescent display that can be seen easily in any lighting condition. The display updates quickly for fast feedback of probe or magnet positioning. The operation is straight forward with display prompts for the user. Max Hold, Alarm, and Sort features are included to streamline sorting and testing operations.

Automation

The Model 421 has a variety of interface features that are compatible with automated test configurations. The RS-232C Serial Interface can perform nearly every function of the instrument front panel. Two analog voltages and an alarm relay facilitate automation without a computer.

Probes

The Model 421 is delivered with one Lake Shore Hall probe of customer choice. A wide range of additional probes is available including Transverse, Axial, Flexible Transverse, and Gamma Probes™. Refer to Paragraph 5.2 for a complete list. Lake Shore probes are factory calibrated for accuracy and interchangeability. Calibration data is loaded into a PROM located in the probe connector so that it does not have to be entered by the user. Lake Shore can also custom design a probe to meet your specific application requirements.

Normal Reading

+102.84 G DC

The Model 421 has a 2 line by 20 character vacuum fluorescent display with resolution to 4¾ digits. The display can accommodate seven measurement ranges from 300.00 mG to 300.00 kG. Measurements are displayed in either gauss or tesla.

Max Hold On

+102.84 G DC +104.38 G MAX

The largest field magnitude seen since the last Max Reset is displayed with the Max Hold function. The maximum value is shown in the lower display while the upper display contains the live reading.

Alarm On

+102.87 G DC ª

The alarm gives an audible and visual indication of when the field value is selectively outside or inside a user specified range. An output relay facilitates pass/fail actuation.

Sort On

+2.522 kG DC ª

The sort function allows the Model 421 to display pass or fail when it is used during repetitive testing. The live reading is shown in the upper display while the lower display contains the pass/fail message.

1-2 Introduction

** Pass **

Lake Shore Model 421 Gaussmeter User’s Manual

1.2 SPECIFICATIONS

General Measurement

Number Of Inputs: 1 Update Rate: 5 readings per second on display;

up to 18 readings with serial interface

Probe Compatibility: Standard and custom probes,

including Model 420 probes Probe Features: Linearity Correction, Auto Probe Zero Measurement Features: Auto Range, Max Hold,

Relative Mode, Filter Connector: 15 pin D style

DC Measurement

DC Display Resolution: 4¾ digits with filter,

3¾ digits without filter

Range Resolution w/Filter Resolution w/out Filter

HST Probe

300 kG 30 kG 3 kG 300 G

HSE Probe

30 kG 3 kG 300 G 30 G

UHS Probe

30 G 3 G 300 mG

DC Accuracy: ±0.20% of reading ±0.05% of range DC Temp. Coefficient: ±0.05% of reading ±0.03% of range/°C

AC RMS Measurement

AC Display Resolution: 3¾ digits

Range Resolution

HST Probe

300 kG 30 kG 3 kG 300 G

HSE Probe

30 kG 3 kG 300 G 30 G

UHS Probe

30 G 3 G 300 mG

AC Frequency Range: 10 – 400 Hz. AC Accuracy: ±2% of reading (50 – 60 Hz.) AC Frequency Response: 0 to –3.5% of reading (10 – 400 Hz.)

(All AC specs for sinusoidal input >1% of range. See Figure 3-3.)

Front Panel

Display Type: 2 line by 20 character, vacuum fluorescent Display Resolution: To ±4¾ digits Display Update Rate: 5 readings per second Display Units: Gauss (G), Tesla (T) Units Multipliers: µ, m, k Annunciators: RMS AC input signal DC DC input signal MAX Max Hold value ° Relative reading R Remote Operation ª Alarm on Keypad: 12 key membrane Front Panel Features: Intuitive operation, display prompts, front

panel lockout, brightness control

0.01 kG

0.001 kG

0.0001 kG

0.01 G

0.001 kG

0.0001 kG

0.01 G

0.001 G

0.0001 G

0.01 mG

0.1 kG

0.01 kG

0.001 kG

0.1 G

0.01 kG

0.001 kG

0.1 G

0.01 G

0.001 G

0.1 mG

0.1 kG

0.01 kG

0.001 kG

0.1 G

0.01 kG

0.001 kG

0.1 G

0.01 G

0.001 G

0.1 mG

Interfaces

RS-232C Capabilities:

Baud: 300, 1200, 9600 Connector: 9 pin D style, DTE configuration Software Support: LabView Driver (consult Lake Shore for

availability). Compatible with Model 420 command set.

Alarm

Settings: High/low setpoint, Inside/Outside, Audible, Sort Actuators: Display annunciator, sort message, beeper, relay

Relay

Number: 1 Contacts: N.O., N.C., and common (C) Contact Rating: 30 VDC at 2 A Operation: Follows alarm Connector: Detachable terminal block

Monitor Analog Output

Configuration: Real-time analog voltage output Range: ±3 V Scale: ±3 V = ±FS on selected range Frequency Response: DC to 400 Hz. Accuracy: Probe dependent

Minimum Load Resistance: 1 kΩ (short-circuit protected)

Connector: BNC

Corrected Analog Output

Configuration: Voltage output generated by DAC Range: ±3 V Scale: ±3 V = ±FS on selected range Resolution: 1.25 mV Update Rate: 5 updates per second Accuracy: ±0.35%

Minimum load resistance: 1 kΩ (short-circuit protected)

Connector: BNC

General

Ambient Temperature: 15 – 35 °C at rated accuracy.

5 – 40 °C with reduced accuracy.

Power Requirement: 100, 120, 220, 240 VAC (+5%, -10%),

50 or 60 Hz, 20 watts

Size: 217 mm W × 90 mm H × 317 mm D, half rack

(8.5 × 3.5 × 12.5 inches) Weight: 3 kilograms (6.6 pounds) Approval: CE Mark

Ordering Information

Part Number Description

Instrument 421 Model 421 Gaussmeter plus one probe

(Specify line voltage and probe model number)

Accessories Included:

106-741 Terminal block for relay outputs 115-006 Detachable line cord (U.S.) 4060 Zero Gauss Chamber MAN-421 Model 421 Gaussmeter User’s Manual

Accessories Available:

RM-1/2 Rack mount kit for one ½ rack gaussmeter

in 483 mm (19 inch) rack

RM-2 Rack mount kit for two ½ rack gaussmeters

in 483 mm (19 inch) rack MCBL-6 User programmable cable with PROM (6 feet) MCBL-20 User programmable cable with PROM (20 feet) MPEC-10 Probe extension cable with EEPROM (10 feet) MPEC-25 Probe extension cable with EEPROM (25 feet) MPEC-50 Probe extension cable with EEPROM (50 feet) MPEC-100 Probe extension cable with EEPROM (100 feet)

(Extension cables must be matched to probes)

One Probe Included (refer to Paragraph 5.2 for details) Custom Probes Available (consult Lake Shore for details) Specifications subject to change without notice.

Introduction 1-3

Lake Shore Model 421 Gaussmeter User’s Manual

1.3 SAFETY SUMMARY

Observe the following general safety precautions during all phases of operation, service, and repair of this instrument. Failure to comply with these precautions or with specific warnings elsewhere in this manual violates safety standards of design, manufacture, and intended use of the instrument. Lake Shore Cryotronics, Inc. assumes no liability for customer failure to comply with these requirements.

The Model 421 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.

• Temperature: 5 – 40 °C.

• Maximum Relative Humidity: 80% for temperatures up to 31

°C decreasing linearly to 50% at 40 °C.

• Power supply voltage fluctuations not to exceed ±10% of the nominal voltage.

Ground The Instrument

To minimize shock hazard, connect instrument chassis and cabinet to an electrical ground. The instrument is equipped with a three-conductor AC power cable; either plug it into an approved threecontact outlet or use a three-contact adapter with the grounding wire (green) firmly connected to a 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.

Do Not Operate In An Explosive Atmosphere

Do not operate the instrument in the presence of flammable gases or fumes. It is a safety hazard.

Keep Away From Live Circuits Inside the Instrument

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

Because of the danger of introducing additional hazards, do not install substitute parts or perform any unauthorized modification to the instrument. Return the instrument to an authorized Lake Shore Cryotronics representative for service and repair to ensure that safety features are maintained.

Do Not Place Conductive Probes Against Exposed Electrical Circuits

Some gaussmeter probes are equipped with conductive sheaths. Keep these probes away from live electrical circuits.

1.4 SAFETY SYMBOLS

1-4 Introduction

Lake Shore Model 421 Gaussmeter User’s Manual

CHAPTER 2

INSTALLATION

2.0 GENERAL

This chapter provides general installation instructions for the Model 421 Gaussmeter. Inspection and unpacking instructions are provided in Paragraph 2.1. Repackaging for shipment instructions are provided in Paragraph 2.2. An definition of rear panel controls is provided in Paragraph 2.3. Finally, an initial setup and system checkout procedure is provided in Paragraph 2.4.

2.1 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, probe(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 Cryotronics, Inc. Warranty is included on the A Page (immediately behind the title page) of this manual.

2.2 REPACKAGING FOR SHIPMENT

If it is necessary to return the Model 421, probe(s), or accessories for 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.

A. Instrument model and serial number.

B. User’s name, company, address, and phone number.

C. Malfunction symptoms.

D. Description of system.

E. 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.

Because of their fragility, Lake Shore probes are shipped in special cardboard and foam boxes. These boxes should be retained for storage of probes while the gaussmeter is not in use. The same box can be used to return probes to Lake Shore for recalibration or repair.

Installation 2-1

Lake Shore Model 421 Gaussmeter User’s Manual

2.3 REAR PANEL DEFINITION

This paragraph provides a description of the Model 421 rear panel connections. The rear panel consists of the line input assembly, Serial I/O Connector, Probe Input Connector, Corrected and Monitor Analog Output BNCs, and Relay Terminal Block. This paragraph is provided for information only. Please read the entire paragraph then proceed to Paragraph 2.8 for the initial setup and system checkout procedure. Rear panel connector pin-out details are provided in Chapter 6 – Service.

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 probe to instrument connections.

421_Rear.bmp

Line Input Assembly Paragraph 2.4 Figure 2-2

SERIAL I/O 9 pin D-Style Connector Paragraph 4.1.1 Figure 6-5

PROBE INPUT 15 pin D-Style Connector Paragraph 2.5 Figure 6-2

Monitor ANALOG OUTPUT BNC Paragraph 2.6 Figure 6-3

Corrected ANALOG OUTPUT BNC Paragraph 2.6 Figure 6-3

RELAY Terminal Block Paragraph 2.7 Figure 6-4

Description Pin Definition

Figure 2-1. Model 421 Rear Panel

2-2 Installation

Lake Shore Model 421 Gaussmeter User’s Manual

2.4 LINE INPUT ASSEMBLY

This section covers line voltage and fuse verification in Paragraph 2.4.1, power cord in Paragraph 2.4.2, and power switch in Paragraph 2.4.3.

2.4.1 Line Voltage and Fuse Verification

To verify proper line voltage selection look at the indicator in the window on the fuse drawer of the line input assembly. Line voltage should be in the range shown in the specifications listed on the back of the instrument. See Figure 2-2. If not, change the line voltage selector per instructions in Paragraph 6.3. The fuse must be removed to verify its value, refer to the procedure in Paragraph 6.4. Use slow-blow fuses of the value specified on back of the instrument.

2.4.2 Power Cord

The Model 421 includes a three-conductor power cord. Line voltage is present across the outer two conductors. The center conductor is a safety ground and connects to the instrument metal chassis. For safety, plug the cord into a properly grounded three-pronged receptacle.

2.4.3 Power Switch

The power switch turns the instrument On and Off and is located in the line input assembly on the instrument rear. When l is raised, the instrument is On. When O is raised, the instrument is Off.

Line Cord

Input

Power Switch

O = Off, l = On

Fuse

Drawer

120

100/120/220/240 V 10% +6% Voltage

50-60 Hz 40 VA MAX

F-421-2-2.eps

100/120V 220/240V

0.5 A T 250V

0.25 A T 250V

0.25×1.25" 5×20mm

Figure 2-2. Line Input Assembly

2.5 PROBE INPUT CONNECTION

WARNING: Some probes used with the gaussmeter have conductive parts. Never probe near

exposed live voltage. Personal injury and damage to the instrument may result.

CAUTION: Always turn off the instrument before making any rear panel Probe Input connections.

Lake Shore probes plug into the 15 pin D-style connector on the Model 421 rear panel. Turn the instrument off before attaching a probe. See Figure 8-3 for pin definitions.

When power is turned on, the instrument reads parameters from probe memory. The probe is ready to use. No parameters need to be entered into the Model 421. However, the Zero Probe function should be performed the first time a probe is used with the instrument and periodically during use.

Installation 2-3

2.5.1 Attachment To A Hall Generator

The Model MCBL-XX has a 15 pin D-Style connector on one end for direct attachment to the PROBE INPUT on the back panel of the Model 421 Gaussmeter. Four tinned wires are provided for connection to the Hall Generator. The leads may be soldered directly to these wires. The cable comes in two lengths: the MCBL-6 is 2 meters (6 feet) and the MCLB-20 is 6 meters (20 feet).

Current to

Lake Shore Model 421 Gaussmeter User’s Manual

Green Wire ()

Sensor

{

Red Wire (+)

Hall Voltage from Sensor

F-421-2-3.eps

Figure 2-3. Model MCBL-XX User Programmable Cable Accessory

CAUTION: The Hall Generator should be isolated from all line voltages (or voltages referenced to

earth ground). If not, damage to the Model 421 Gaussmeter is almost a certainty.

Refer to Appendix C for a complete list of compatible Hall generators manufactured by Lake Shore. Once connections are made, refer to Paragraph C6.0 for instructions on using the Hallcall.exe program to store probe parameters in the internal EPROM.

2.6 CORRECTED AND MONITOR ANALOG OUTPUTS

Analog outputs are available on two Bayonet Nut Connectors (BNCs). The signal is on the center conductor while the outer casing is for ground. Both outputs may be used simultaneously. The corrected output is not a real-time signal, but is updated at the same rate as the display. The range of the corrected output is ±3 volts equals ± full scale for the range. The monitor output is a live analog signal proportional to the magnetic flux density waveform. Refer to Paragraph 3.10 for further operational information.

2.7 RELAY TERMINAL BLOCK

The Model 421 has a single relay output that follows the alarm state. The relay outputs have a detachable 3-pin terminal block connector. The connector (included with the Model 421) can be removed from its socket for convenient installation of wires. The connector manufacturer indicates that up to 12 AWG stranded copper wire can be used with the connector.

CAUTION: Always turn off the instrument before making any rear panel terminal block connections.

The terminal block has normally open (NO), normally closed (NC), and common (C) contacts in a Single Pole Double Throw (SPDT) configuration. The instrument provides no power through the relay; it opens and closes as switches relative to the alarm state. The contacts are rated at 30 VDC at 2 A. Refer to Paragraph 3.9 for alarm and relay operation.

Blue Wire (+)

{

Yellow Wire ()

Terminal Description

1 Normally Closed (NC)

2 Common (C)

3 Normally Open (NO)

6 Foot Cable to

Gaussmeter

2-4 Installation

Lake Shore Model 421 Gaussmeter User’s Manual

2.8 INITIAL SETUP AND SYSTEM CHECKOUT PROCEDURE

The following procedure is an initial instrument setup and checkout procedure. The intent of this procedure is to verify basic operation of the unit before beginning use for measurements.

CAUTION: Check power source for proper voltage before connecting the line cord to the

Model 421. Also check the power 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 421 operates with 100, 120, 220, or 240 (+5%, –10%) AC input voltage.

2. Check window in fuse drawer for proper voltage setting. If incorrect, refer to Paragraph 5.2.

3. Ensure the power switch is in the off (O) position.

CAUTION: The probe must be connected to the rear of the unit before applying power to the

gaussmeter. Damage to the probe may occur if connected with power on.

4. Plug in the probe connector to PROBE INPUT. Use thumbscrews to tighten connector to unit.

5. Ensure any other rear panel connections (SERIAL I/O or ANALOG OUTPUTS) are connected before applying power to the unit.

6. Plug line cord into receptacle.

7. Turn the power switch to the on (l) position. The front panel display should turn on and the following message briefly appear.

Lake Shore 421 Field Monitor

8. The normal gaussmeter display will now appear. A typical display is illustrated below.

+ 0.001 G DC

NOTE: For best results, the instrument and probe should warm up for at least 5 minutes before

zeroing the probe, and at least 30 minutes for rated accuracy. The probe and the zero gauss chamber should be at the same temperature.

NOTE: Some Lake Shore probes come with a clear plastic sleeve to protect the probe tip when not

in use. The sleeve slides up and down the probe cable. To place the probe in the zero gauss chamber, slide the protective sleeve back, exposing the probe tip, before placing the tip in the chamber.

9. If so equipped, slide the clear plastic sleeve back, exposing the tip of the probe. Place the probe in the zero gauss chamber and press the front panel Zero Probe key. The display below appears.

Press Enter With Probe At Zero

Installation 2-5

INITIAL SETUP AND SYSTEM CHECKOUT PROCEDURE (Continued)

Lake Shore Model 421 Gaussmeter User’s Manual

10. Press the Enter key. The *CALIBRATING* message will briefly be displayed, followed by a return

to the normal display.

NOTE: If the unit has performed well to this point, the unit is functioning properly. If you have a

reference magnet available, you can continue with the test using the magnet to verify the accuracy of the Model 421.

11. If continuing the procedure with a reference magnet, ensure the probe can accommodate the range of the magnet. Use the Range key to select the proper range. Set the display for DC. Finally, since orientation of the probe is very selective, press the Max Hold key. This will capture the highest reading (normally the reference magnet calibration value).

CAUTION: Care must be exercised when handling the probe. The tip of the probe is very

fragile. Any excess force may break the probe.

NOTE: Probe readings are dependent upon the angle of the tip in relation to the magnetic field.

This and other effects on probe operation are explained in Paragraph 3.16.

12. Carefully place probe into reference magnet. You may have to hunt around a bit for the maximum reading. For this example, we are using a 999 ±1% Gauss Reference Magnet. Our reading appeared as follows:

+ 0.9720 kG DC

0.9950 kG MAX

On the top line, the current reading is +0.9720 kG DC. On the bottom line, the maximum reading captured was 0.9950 kG, which is within the tolerance of the reference magnet. The top line will keep changing as the probe moves, but the bottom will remain fixed on the highest reading. To recapture a new maximum value, press the Max Reset key.

Once this abbreviated checkout procedure is successfully completed, the unit is ready for normal operation. Please proceed to Chapter 3 for further operational information.

2-6 Installation

Lake Shore Model 421 Gaussmeter User’s Manual

CHAPTER 3

OPERATION

3.0 GENERAL

This chapter describes Model 421 Gaussmeter operation. The front panel controls are described in Paragraph 3.1. Paragraphs 3.2 thru 3.14 describe the various front panel functions in detail. Model 421 default settings are defined in Paragraph 3.15. Finally, Paragraph 3.16 provides probe handling considerations. Refer to Chapter 4 for detailed information on remote operation (serial interface).

3.1 DEFINITION OF FRONT PANEL CONTROLS

This paragraph provides a description of the front panel controls on the Model 421.

3.1.1 Front Panel Keypad

The keys on the front panel are defined as follows. Note the following are abbreviated descriptions of each key. A more detailed description of each function is provided in subsequent paragraphs.

Max Reset Works with the Max Hold function. Clears Max reading back to current reading.

Press and hold to reset parameters to default values. This key also acts as an

Max Hold Turns the Max Hold feature on and off. Use Max Reset key to clear reading.

Zero Probe Used to zero or null effects of ambient low level fields from the probe.

Range Selects a manual field measurement range or Autorange. Available ranges are

AC/DC Selects periodic AC (RMS) or static (DC) magnetic fields. Press and hold to turn

escape key during numeric entry.

Press and hold to lock keypad.

dependent on which probe is installed.

Filter on or off.

421_Front.bmp

Operation 3-1

Figure 3-1. Model 421 Front Panel

Lake Shore Model 421 Gaussmeter User’s Manual

Front Panel Keypad Definitions (Continued)

Gauss/Tesla Changes display units from gauss to tesla. Gauss (G) is used in the cgs system, tesla

(T) is used in the SI system, where 1 T = 10

Relative Used to capture a relative setpoint, the display shows the positive or negative

deviation from that setpoint. Press and hold to adjust the brightness of the vacuum florescent display.

Interface The Serial Interface baud rate of the Model 421 transmissions may be changed from

300, 1200, or 9600. Press and hold to initiate Fast Data Mode from the front panel.

Alarm Turns alarm feature on or off and allows entry of alarm setpoints. Press and hold to

turn the audible beeper on or off, select the alarm to operate inside or outside the setpoint range, and turn the sort feature on or off.

s Toggles between various settings shown in the display and increments a numerical

display.

t Toggles between various settings shown in the display and decrements a numerical

display.

Enter Accepts changes to parameter setting.

3.1.2 Front Panel Display

In normal operation, the 2 row by 20 character vacuum fluorescent display provides current magnetic readings on the top row and special information or readings on the bottom row. Other information is displayed when using the various functions on the keypad. Each character is comprised of a 5 by 7 dot matrix. See Figure 3-2. To change the display brightness, prefer to Paragraph 3.14.

Probe Orientation

(DC Only)

Current Reading

Units:

µT

RMS

Relative

Alarm

Lower row used for Max Hold (MAX) (shown above) and Relative

C-421-3-2.eps

Figure 3-2. Front Panel Display Definition

3-2 Operation

Setpoint (SP) readings. Also used for various on/off messages.

Lake Shore Model 421 Gaussmeter User’s Manual

3.1.3 General Keypad Operation

Human interface with the instrument is provided by the 12 buttons that comprise the front panel keypad. Most operations can be performed through the front-panel keypad and monitored by watching the front panel display.

NOTE: Timeout is treated as escape, i.e., any changes made will not be retained if the display

There are five basic keypad operations:

times out and returns to the main display.

1. Direct Operation: The following key functions occurs upon pressing the key: Max Reset, Max Hold, Zero Probe, AC/DC, Gauss/Tesla, and Relative.

2. Direct Operation After Press And Hold: The following key functions occurs immediately after pressing and holding a key: Set Defaults, Lock Keypad, and Fast Data Mode.

3. Setting Selection: The following functions will display a selection of settings immediately upon pressing a key: Range, Baud Rate, and Alarm On/Off. The arrow keys are active when you see the “°®” symbol on the display. Pressing the Enter key will enter parameter changes and return you to the main screen.

4. Setting Selection After Press And Hold: The following functions will display a selection of settings after pressing and holding a key: Filter, Brightness, Audible Alarm, Alarm Inside/Outside, and Sort. The arrow keys are active when you see the “°®” symbol on the display. Pressing the Enter key will enter parameter changes and return you to the main screen.

5. Numeric Data Entry: The high and low alarm setpoints require numeric data entry. Numbers can be entered with up to 5 digits of resolution in any field range available for the probe being used.

To begin number entry look at the range and resolution of the present parameter value. If it is too small to accommodate the new value, or too large to allow appropriate resolution, change the setting range by pressing the Range key. Pressing the Range key will cycle through all available setting ranges and zero the setting value.

The most significant digit of the entry value will blink to indicate that digit can be changed. Use the s or t keys to change that digit to the desired value. Digits should be set to zero if not used. Press the Enter key to advance to the next digit. Continue until all digits are set. When the Enter key is pressed on the last digit the setting value will be stored. If a mistake is made press the Range key to select a new range and start over or press Max Reset to escape out of the setting function.

3.2 GAUSS/TESLA

The Model 421 displays magnetic field values in gauss (G) or tesla (T). Pressing the Gauss/Tesla key toggles the display between the two units. The relation between gauss and tesla is 1 G = 0.0001 T, or 1 T = 10,000 G. When the field units are changed, relative and alarm setpoints are converted to the new units with no interruption in operation. The Corrected and Monitor Analog Outputs are not affected by a change in units.

When tesla is selected, the Model 421 displays AC or DC field values followed by T for tesla, mT for millitesla, or µT for microtesla. Field values available over the Serial Interface are formatted accordingly.

When gauss is selected, the Model 421 displays AC or DC field values followed by kG for kilogauss, G for gauss, or mG for milligauss. The field value available over the Serial Interface is formatted accordingly.

Operation 3-3

Lake Shore Model 421 Gaussmeter User’s Manual

3.3 AC/DC

Pressing the AC/DC key toggles between AC and DC measurements. The annunciator immediately changes from DC to RMS, as applicable. However, one update cycle is required for a new display value.

In DC operation, the display shows the DC field at the probe with sign (orientation) followed by the appropriate field units and the letters DC. The DC value is available over the Serial Interface and both Analog Outputs. The resolution of DC readings is 3¾ digits when the filter feature is turn off and 4¾ digits when the filter is turned on.

In AC operation, the RMS readings will meet specified accuracy from 10 to 400 Hz. The AC RMS value is defined as the square root of the average of the square of the value of the function taken throughout one period. Frequency response and noise dominate the error present in AC mode. The Model 421 has a predictable frequency response which is illustrated in Figure 3-3.

The RMS value is available over the Serial Interface. A DC voltage representation of the RMS display reading is available from the Corrected Analog Output, while a true analog waveform is available from the Monitor Analog Output. (In fact, the Monitor Analog Output is not affected by the selection of AC or DC.) The resolution of AC RMS readings is fixed at 3¾ digits.

P-421-3-3.bmp

Figure 3-3. Model 421 AC Frequency Response

3.4 DISPLAY FILTER

The display filter function is used to quiet the display and make it more readable when the probe is exposed to a noisy field. Care should be taken when using the filter on changing fields because it may level off peaks and slow the response of the instrument. The filter also acts to quiet noise within the instrument, making an additional digit of usable resolution available with the filter on in DC. The filter function makes a linear average of 8 readings and settles in approximately 2 seconds.

To turn on the display filter, press and hold the AC/DC key for 5 seconds. The following display will appear.

Select With °® Filter On ¡Off

Use the s or t keys to toggle between On and Off. Press the Enter key to accept the new setting.

3-4 Operation

Lake Shore Model 421 Gaussmeter User’s Manual

3.5 MANUAL RANGE AND AUTO RANGE

The Model 421 is capable of reading each of the Lake Shore probe types: High Stability (HST), High Sensitivity (HSE), or Ultra-High Sensitivity (UHS). The three probes permit the Model 421 to be used with ranges of 300 mG to 300 kG. The full-scale ranges for each probe type, along with the display resolution, are shown as follows.

Range

HST Probe

300 kG 30 kG 3 kG 300 G

HSE Probe

30 kG 3 kG 300 G 30 G

UHS Probe

30 G 3 G 300 mG

DC Resolution

with Filter

0.01 kG

0.001 kG

0.0001 kG

0.01 G

0.001 kG

0.0001 kG

0.01 G

0.001 G

0.0001 G

0.01 mG

DC Resolution

without Filter

0.1 kG

0.01 kG

0.001 kG

0.1 G

0.01 kG

0.001 kG

0.1 G

0.01 G

0.001 G

0.1 mG

AC RMS

Resolution

0.1 kG

0.01 kG

0.001 kG

0.1 G

0.01 kG

0.001 kG

0.1 G

0.01 G

0.001 G

0.1 mG

For manual ranging, pressing the Range key and the following display will appear.

Select With °® +/- 3.000 kG

Use the s or t keys to toggle through the allowable full scale ranges for the probe installed. Press the Enter key to accept the new setting.

In Auto Range mode, the Model 421 selects the range with the best resolution for the field being measured. It can take up to 2 seconds for Auto Range to work, so manual ranging may be better in some conditions. Press the Range key.

Select With °® Auto Range

Use the s or t keys to toggle through the allowable full scale ranges until Auto Range is displayed. Press the Enter key to accept the new setting.

Auto Range should not be used with Max Hold operation or when alarms are active. Also, Auto Range should not be used when measuring small fields in a large background field, i.e., measuring a small DC field in presence of a large AC field, or measuring a small AC field in the presence of a large DC field.

Operation 3-5

Lake Shore Model 421 Gaussmeter User’s Manual

3.6 ZERO PROBE

The zero probe function is used to null (cancel) out the zero offset of the probe or small magnetic fields. It is normally used in conjunction with the zero gauss chamber, but may also be used with an open probe (registering the local Earth magnetic field). Users wishing to cancel large magnetic fields should use the Relative function.

NOTE: For best results, the instrument and probe should warm up for at least 5 minutes

before zeroing the probe, and at least 30 minutes for rated accuracy. The probe and the zero gauss chamber should be at the same temperature.

To zero the probe in the zero gauss chamber, first allow the temperature of the probe and chamber to be approximately equal. (A large temperature discrepancy affects the quality of the calibration.) Carefully place the probe tip into the chamber. Orientation of the probe is not critical. Once inserted, press the Zero Probe key and observe the following display.

Press Again With Probe At Zero

Press the Zero Probe key. The *CALIBRATING* message is briefly displayed, followed by a return to the normal display. The probe is now calibrated. For best results, periodic zeroing of the probe is recommended.

3.7 MAX HOLD AND MAX RESET

The Max Hold function displays the largest field magnitude measured since the last Max Reset. When the Max Hold key is pressed, the maximum value is shown in lower line of the display while the upper line contains the current field reading.

+2.483 kG DC

2.544 kG MAX

The Max Reset key clears the hold value. The hold value is also reset upon power up or when changing from AC or DC. Max Hold may also be used in conjunction with the Relative display (refer to Paragraph 3.8).

In DC operation, the Max Hold feature holds the field reading that is largest in magnitude. This is intended to monitor slowly changing signals. A field change not visible on the display can not be recorded in DC Max Hold. The display shows only the magnitude of the largest reading.

In AC RMS operation, the maximum RMS value is held.

3-6 Operation

Lake Shore Model 421 Gaussmeter User’s Manual

3.8 RELATIVE

The relative function lets the user see small variations in larger fields. The setpoint (or center) of the relative reading is set when pressing the Relative key. This captures the current reading and effectively nulls the present field.

+1.420 kG DC Relative On

Once the Relative key is pressed, the Relative On message is briefly shown on the lower line of the display. This is followed with the selected setpoint (SP) being displayed on the lower line and the current plus or minus deviation from that setpoint on the upper line. A small delta (°) is also displayed to signify the relative display.

+0.000 kG DC ° +1.420 kG SP

The relative feature also interacts with other features. When Relative and Max Hold functions are used at the same time, the relative reading is still in the top display with proper annunciators, but the bottom display shows the relative maximum instead of the relative setpoint.

+0.002 kG DC ° +0.010 kG MAX

Pressing Max Hold again turns off the maximum hold function, returning the relative setpoint to the display. Pressing the Relative key turns off the relative function. The Relative Off message is briefly displayed.

3.9 ALARM AND RELAY

The alarm feature can be easily configured to perform several different tasks including error detection and limit testing. The most powerful application is manual magnet testing and sorting. A display annunciator, message display, beeper, and relay are all available to indicate an active alarm state. This section describes all of the parameters available for the alarm feature then gives examples to illustrate operation under different conditions.

When the alarm feature is on the alarm annunciator (ª) will appear in the top display. If there is an alarm condition the annunciator will flash to indicate the alarm is active. If there is not an alarm condition the annunciator will remain steady to indicate the alarm is in its normal state. Beeper and relay operation follow the alarm condition in a similar way when they are in use. The alarm function is non-latching so no action is required to reset the alarm. The alarm resets automatically when the alarm condition is no longer present.

To turn the alarm feature on press the Alarm key and the following display will appear.

Use the s or t keys to select between Alarm On and Off and press Enter to accept the new setting.

Operation 3-7

Select With °® Alarm ¡On Off

ALARM AND RELAY (Continued)

Lake Shore Model 421 Gaussmeter User’s Manual

When the alarm is turned on, two additional setting screens will appear for high and low alarm setpoints. These values establish the limit for an error condition or the pass/fail limits for magnet testing. The values can be entered with the display resolution on any range available for the probe being used. The setpoint values are entered as positive numbers since the alarm feature uses the absolute (unsigned) value of field for comparison. Operation of the alarm setpoints is best understood when viewing the alarm inside/outside parameter examples below.

To enter the high alarm setpoint continue from Alarm On/Off or press the Alarm key and press the Enter key until the following display appears.

Enter High Alarm

1.5000 kG

The high alarm setpoint requires numeric data entry. Numbers can be entered with up to 5 digits of resolution in any field range available for the probe being used.

After entering the desired high alarm point, press Enter to accept the new value. The display proceeds to the Low Alarm Point as follows:

Enter Low Alarm

0.5000 kG

The low alarm setpoint requires numeric data entry. Numbers can be entered with up to 5 digits of resolution in any field range available for the probe being used.

The alarm setpoints are absolute (unsigned) i.e., only the magnitude of the field reading is used.

3-8 Operation

ALARM AND RELAY (Continued)

Lake Shore Model 421 Gaussmeter User’s Manual

The Model 421 has an audible alarm annunciator or beeper. The beeper will sound when the instrument is in an active alarm state. If the sound of the beeper is not appropriate for your application, it can be turned on or off by the user. To turn the beeper on or off, press and hold the Alarm key until the following message appears.

Select With °® Audible ¡On Off

Use the s or t keys to cycle between audible alarm On or Off. Press Enter to accept the new value.

When the alarm feature is used to detect an error condition an active alarm state is expected when the field reading is higher than the high alarm setpoint or below the low alarm setpoint. This operation is achieved by setting the inside/outside parameter to outside. It is called outside because the alarm is active when the reading is outside the range of the two setpoints. During magnet testing or sorting it is often desirable to have the alarm active when the field reading is inside or between the two setpoints. This operation is achieved by setting the inside/outside parameter to inside. (see examples below)

To select inside/outside alarm operation, continue from Audible On/Off screen or press and hold the Alarm key until the Audible setting window appears, then press Enter until the following message appears.

Select With °® Alarm ¡In Out

Use the s or t keys to cycle between the alarm triggered inside (In) or outside (Out) alarm setpoints. Press Enter to accept the changes.

Model 421 can be configured to display pass or fail when it is used during repetitive magnet testing or sorting operations. The sort message can be turned on or off as necessary and does not affect other operations of the alarm feature. When sort is turned on the lower display line will show:

Fail Low Field below low alarm setpoint.

** Pass ** Field between the two alarm setpoints.

Fail High Field above high alarm setpoint.

The message will use the lower display line during max hold or relative measurements. The live reading will be replaced during max hold operation and the relative setpoint will be replaced during relative operation.

To enable the sort message continue from Inside/Outside or press and hold the Alarm key until the Audible setting window appears then press the Enter key until the following message appears.

Use the s or t keys to select between Sort On and Off, then press Enter to accept the new setting.

Operation 3-9

Select With °® Sort ¡On Off

ALARM AND RELAY (Continued)

Lake Shore Model 421 Gaussmeter User’s Manual

The Model 421 has a single relay that is associated with alarm operation. The relay changes to its active state when the alarm is active and remains in its normal state when the alarm is not active. Relay terminals are located in a detachable terminal block on the instrument rear panel as described in Paragraph 2.7.

The following example details operation with the Alarm Outside setting. For example, if the reading is to be centered on 1 kG, with the high alarm point at 1.5 kG and the low alarm point at 0.5 kG, the following diagram illustrates when the alarm would be active or normal.

Alarm

Off

Alarm

Off

Alarm

3 kG 2 kG 1 kG

Example of operation

with alarm triggered by

readings OUTSIDE

user defined setpoints.

0 kG +1 kG +2 kG +3 kG

Low Alarm

Point

High Alarm Point

The following example details how the alarm operates in the Alarm Inside setting. The alarm inside setup is useful in situations where the user is looking for an indication of a good reading, such as incoming inspections. For example, you may be sorting a number of 1 kG magnets. The magnets have an acceptable tolerance of ±0.25 kG. With the high alarm point set to 1.25 kG and the low alarm point at 0.75 kG, the following diagram illustrates when the alarm would be active or normal.

Alarm

Off

Alarm

3 kG 2 kG 1 kG

Example of operation

with alarm triggered by

readings INSIDE user

defined setpoints

Alarm

Off

0 kG +1 kG +2 kG +3 kG

Low Alarm

Point

High Alarm Point

Alarm

Off

3.10 ANALOG OUTPUTS

There are two analog outputs available on the rear panel of the Model 421. They are the Corrected and Monitor Analog Outputs. Both outputs use BNC connectors with the center conductor carrying the signal and the outer portion the ground.

The Corrected Analog Output is a DC value proportional to the displayed field. The displayed field reading is corrected for probe nonlinearity and zero offset. This output is not a real time signal, but is updated at the same rate as the display. The range of the Corrected output is ±3 volts equals ± full scale for the selected range.

3-10 Operation

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Lake Shore Model 421 User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual