Page 1
Via Acquanera, 29 22100 Como
tel. 031.526.566 (r.a.) fax 031.507.984
info@calpower.it www.calpower.it
7312
Triple Point of Water Maintenance Bath
March 2013
© 2013 Fluke Corporation. All rights reserved. Specifications are subject to change without notice.
All product names are trademarks of their respective companies.
User’s Guide
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Page 4
6.3 Comparison Calibration . . . . . . . . . . . . . . . . . . . . . . . 27
6.4 Calibration of Multiple Probes . . . . . . . . . . . . . . . . . . . 27
7 Parts and Controls . . . . . . . . . . . . . . . . . . . . . . . . 29
7.1 Front Panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
7.2 Bath Tank and Lid . . . . . . . . . . . . . . . . . . . . . . . . . . 30
7.3 Back Panel. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
8 General Operation . . . . . . . . . . . . . . . . . . . . . . . . 31
8.1 Heat Transfer Fluid . . . . . . . . . . . . . . . . . . . . . . . . . 31
8.1.1 Temperature Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
8.1.2 Viscosity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
8.1.3 Specific Heat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
8.1.4 Thermal Conductivity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
8.1.5 Thermal Expansion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
8.1.6 Electrical Resistivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
8.1.7 Fluid Lifetime . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
8.1.8 Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
8.1.9 Cost . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
8.1.10 Commonly Used Fluids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
8.1.10.1 Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
8.1.10.2 Ethylene Glycol. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
8.1.10.3 Mineral Oil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
8.1.10.4 Silicone Oil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
8.1.11 Fluid Characteristics Charts. . . . . . . . . . . . . . . . . . . . . . . . . . . 35
8.1.11.1 Limitations and Disclaimer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
8.1.11.2 About the Graph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35
8.2 Stirring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
8.3 Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
8.4 Heater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
8.5 Temperature Controller . . . . . . . . . . . . . . . . . . . . . . . 38
8.6 Refrigeration . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
9 Controller Operation . . . . . . . . . . . . . . . . . . . . . . . 41
9.1 Bath Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . 41
9.2 Reset Cutout. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
9.3 Temperature Set-point . . . . . . . . . . . . . . . . . . . . . . . . 43
9.3.1 Programmable Set-points . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
9.3.2 Set-point Value . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
9.3.3 Set-point Vernier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
9.4 Temperature Scale Units . . . . . . . . . . . . . . . . . . . . . . 45
9.5 Secondary Menu. . . . . . . . . . . . . . . . . . . . . . . . . . . 46
9.6 Heater Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
9.7 Proportional Band . . . . . . . . . . . . . . . . . . . . . . . . . . 46
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9.8 Cutout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
9.9 Controller Configuration . . . . . . . . . . . . . . . . . . . . . . 50
9.10 Probe Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . 50
9.10.1 D0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
9.10.2 DG. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
9.11 Operating Parameters . . . . . . . . . . . . . . . . . . . . . . . . 50
9.11.1 Cutout Reset Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
9.11.2 Triple Point of Water Cutout . . . . . . . . . . . . . . . . . . . . . . . . . . 51
9.12 Serial Interface Parameters . . . . . . . . . . . . . . . . . . . . . 52
9.12.1 BAUD Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
9.12.2 Sample Period. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
9.12.3 Duplex Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
9.12.4 Linefeed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
9.13 IEEE-488 Parameters . . . . . . . . . . . . . . . . . . . . . . . . 54
9.13.1 IEEE-488 Address . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
9.13.2 Transmission Termination . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
9.14 Calibration Parameters . . . . . . . . . . . . . . . . . . . . . . . 55
9.14.1 CTO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
9.14.2 H and L . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
10 Digital Communication Interface . . . . . . . . . . . . . . . . 57
10.1 Serial Communications . . . . . . . . . . . . . . . . . . . . . . . 57
10.1.1 Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
10.1.2 Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
10.1.2.1 BAUD Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
10.1.2.2 Sample Period. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
10.1.2.3 Duplex Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
10.1.2.4 Linefeed. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
10.1.3 Serial Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
10.2 IEEE-488 Communication (optional) . . . . . . . . . . . . . . . . 59
10.2.1 Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
10.2.1.1 IEEE-488 Address . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
10.2.1.2 Transmission Termination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
10.2.2 IEEE-488 Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
10.3 Interface Commands . . . . . . . . . . . . . . . . . . . . . . . . 60
10.4 Power Control Functions . . . . . . . . . . . . . . . . . . . . . . 63
11 Calibration Procedure . . . . . . . . . . . . . . . . . . . . . . 65
11.1 Calibration Points—2 Point Calibration. . . . . . . . . . . . . . . 65
11.2 Measuring the Set-point Error . . . . . . . . . . . . . . . . . . . . 65
11.3 Computing DO and DG . . . . . . . . . . . . . . . . . . . . . . . 65
11.4 Calibration Example. . . . . . . . . . . . . . . . . . . . . . . . . 66
11.5 Single Point Calibration . . . . . . . . . . . . . . . . . . . . . . . 66
11.6 Measuring the Set-point Error . . . . . . . . . . . . . . . . . . . . 67
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11.7 Computing D0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
11.8 Calibrating the Triple Point of Water Cutout . . . . . . . . . . . . 68
12 Charging Instructions . . . . . . . . . . . . . . . . . . . . . . 71
12.1 Leak Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
12.2 Evacuation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
12.3 Charging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
13 Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
14 Troubleshooting. . . . . . . . . . . . . . . . . . . . . . . . . . 75
14.1 Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
14.2 Comments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
14.2.1 EMC Directive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
14.2.2 Low Voltage Directive (Safety). . . . . . . . . . . . . . . . . . . . . . . . . 78
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Figures and Tables
Figure 1 Drain Valve Installation—IMPORTANT: Do Not Over Tighten.
Follow the installation instructions above. . . . . . . . . . . . . . . . . 18
Figure 2 Details of the Access Cover and Cell Racks . . . . . . . . . . . . . . . 23
Figure 3 Fluid Level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Figure 4 Location of Handles for NBS Design Cells . . . . . . . . . . . . . . . 26
Figure 5 Front Controller Panel . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Figure 6 Chart of Various Bath Fluids and Their Properties . . . . . . . . . . . 37
Figure 7 Controller Operation Flowchart . . . . . . . . . . . . . . . . . . . . . 42
Figure 8 Bath Temperature Fluctuation at Various Proportional Band Settings . . 47
Figure 9 Serial Communications Cable Wiring . . . . . . . . . . . . . . . . . . 58
Figure 10 Sample Calibration Computations . . . . . . . . . . . . . . . . . . . . 67
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Tables
Table 1 International Electrical Symbols . . . . . . . . . . . . . . . . . . . . . 1
Table 2 Table of Various Bath Fluids and Their Properties. . . . . . . . . . . . 36
Table 3 Proportional Band - Fluid Table . . . . . . . . . . . . . . . . . . . . . 48
Table 4 Interface Command Summary.. . . . . . . . . . . . . . . . . . . . . . 61
Table 4 Interface Command Summary continued . . . . . . . . . . . . . . . . 62
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1 Before You Start
1.1 Symbols Used
Table 1 lists the International Electrical Symbols. Some or all of these symbols
may be used on the instrument or in this manual.
Table 1 International Electrical Symbols
Symbol Description
AC (Alternating Current)
AC-DC
1 Before You Start
Symbols Used
Battery
CE Complies with European Union Directives
DC
Double Insulated
Electric Shock
Fuse
PE Ground
Hot Surface (Burn Hazard)
Read the User’s Manual (Important Information)
Off
On
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7312 TPW Maintenance Bath
User’s Guide
Symbol Description
Canadian Standards Association
OVERVOLTAGE (Installation) CATEGORY II, Pollution Degree 2 per IEC1010-1 re
fers to the level of Impulse Withstand Voltage protection provided. Equipment of
OVERVOLTAGE CATEGORY II is energy-consuming equipment to be supplied from
the fixed installation. Examples include household, office, and laboratory appliances.
C-TIC Australian EMC Mark
The European Waste Electrical and Electronic Equipment (WEEE) Directive
(2002/96/EC) mark.
1.2 Safety Information
Use this instrument only as specified in this manual. Otherwise, the protection
provided by the instrument may be impaired.
The following definitions apply to the terms “Warning” and “Caution”.
• “WARNING” identifies conditions and actions that may pose hazards to
the user.
• “CAUTION” identifies conditions and actions that may damage the in-
strument being used.
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1.2.1
WARNINGS
To avoid possible electric shock or personal injury, follow these guidelines.
GENERAL
•
DO NOT use the instrument for any application other than calibration
work. The instrument was designed for temperature calibration. Any other
use of the unit may cause unknown hazards to the user.
•
DO NOT use the unit in environments other than those listed in the user’s
guide.
•
DO NOT overfill the bath. Overflowing extremely cold or hot fluid may
be harmful to the operator. See Section 5.3, Bath Preparation and Filling,
for specific instructions.
•
Follow all safety guidelines listed in the user’s manual.
•
Calibration Equipment should only be used by Trained Personnel.
•
If this equipment is used in a manner not specified by the manufacturer,
the protection provided by the equipment may be impaired.
•
Before initial use, or after transport, or after storage in humid or semi-hu
mid environments, or anytime the instrument has not been energized for
more than 10 days, the instrument needs to be energized for a "dry-out"
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1 Before You Start
Safety Information
period of 2 hours before it can be assumed to meet all of the safety re
quirements of the IEC 1010-1. If the product is wet or has been in a wet
environment, take necessary measures to remove moisture prior to apply
ing power such as storage in a low humidity temperature chamber operat
ing at 50 degree centigrade for 4 hours or more.
DO NOT operate high temperature baths (500°C) near flammable materi
•
als. Extreme temperatures could ignite the flammable material.
Overhead clearance is required. Do not place the instrument under a cabi
•
net or other structure. Always leave enough clearance to allow for safe
and easy insertion and removal of probes.
The instrument is intended for indoor use only.
•
BURN HAZARD
Extremely cold temperatures may be present in this equipment. Freezer
•
burns and frostbite may result if personnel fail to observe safety precau
tions.
• High temperatures may be present in this equipment. Fires and severe
burns may result if personnel fail to observe safety precautions.
ELECTRICAL HAZARD
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-
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• These guidelines must be followed to ensure that the safety mechanisms
in this instrument will operate properly. This instrument must be plugged
into a 115 VAC, 60Hz (230 VAC, 50Hz optional), AC only electric outlet.
The power cord of the instrument is equipped with a three-pronged
grounding plug for your protection against electrical shock hazards. It
must be plugged directly into a properly grounded three-prong receptacle.
The receptacle must be installed in accordance with local codes and ordi-
nances. Consult a qualified electrician. DO NOT use an extension cord or
adapter plug.
•
DO use a ground fault interrupt device. This unit contains a liquid. A
ground fault device is advised in case liquid is present in the electrical
system and could cause an electrical shock.
•
Always replace the power cord with an approved cord of the correct rat
ing and type. If you have questions, contact a Hart Scientific Authorized
Service Center (see Section 1.3).
•
High voltage is used in the operation of this equipment. Severe injury or
death may result if personnel fail to observe the safety precautions. Before
working inside the equipment, turn off the power and disconnect the
power cord.
BATH FLUIDS
-
•
Fluids used in this unit may produce noxious or toxic fumes under certain
circumstances. Consult the fluid manufacturer’s MSDS (Material Safety
Data Sheet). Proper ventilation and safety precautions must be observed.
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7312 TPW Maintenance Bath
User’s Guide
The instrument is equipped with a soft cutout (user settable firmware) and
•
a hard cutout (set at the factory). Check the flash point, boiling point, or
other fluid characteristic applicable to the circumstances of the unit opera
tion. Ensure that the soft cutout is adjusted to the fluid characteristics of
the application. As a guideline, the soft cutout should be set 10°C to 15°C
below the flash point of the bath fluid. See Section 8.1, Heat Transfer
Fluid, for specific information on bath fluids and Section 9.8, Cutout.
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1.2.2
CAUTIONS
To avoid possible damage to the instrument, follow these guidelines.
THE DRAIN VALVE MUST BE INSTALLED ON THE BACK OF
•
THE BATH BEFORE ATTEMPTING TO FILL THE TANK WITH
FLUID. See Section 5.3, page 17 for drain installation instructions.
• Always operate this instrument at room temperature between 41°F and
122°F (5°C to 50°C). Allow sufficient air circulation by leaving at least 6
inches (15 cm) of clearance around the instrument.
• DO NOT overfill the bath. Overflowing liquid may damage the electrical
system. Be sure to allow for thermal expansion of the fluid as the bath
temperature increases. See Section 5.3, Bath Preparation and Filling, for
specific instructions.
• Read Section 7, Bath Use, before placing the unit into service.
• DO NOT change the values of the bath calibration constants from the fac-
tory set values. The correct setting of these parameters is important to the
safety and proper operation of the unit.
• The refrigeration may be damaged or the lifetime shortened if the
set-point temperature is set above 60°C for more than one hour with the
refrigeration manually on. Ensure that the refrigeration is off when the
unit is used above 60°C.
•
The Factory Reset Sequence should be performed only by authorized
personnel if no other action is successful in correcting a malfunction. You
must have a copy of the most recent Report of Test to restore the test pa
-
rameters.
•
DO NOT operate this instrument in an excessively wet, oily, dusty, or
dirty environment.
•
The unit is a precision instrument. Although it has been designed for opti
mum durability and trouble free operation, it must be handled with care.
Position the unit before the tank is filled with fluid. Use the handles pro
vided to move the unit. Due to the weight of the compressor, it may re
-
quire two people to safely move the bath. If two people are used, place
one person in the front and one person in the back of the unit, carefully
slide hands under the unit and lift in unison. The area containing the com
-
pressor will be heavier than the rest of the unit. Do not move a unit filled
with fluid.
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1 Before You Start
Authorized Service Centers
Most probes have handle temperature limits. Be sure that the probe handle
•
temperature limit is not exceeded in the air above the instrument.
The instrument and any thermometer probes used with it are sensitive in
•
struments that can be easily damaged. Always handle these devices with
care. Do not allow them to be dropped, struck, stressed, or overheated.
COLD BATHS
Refrigerated baths require that the condensing coil be cleaned periodi
•
cally. Accumulation of dust and dirt on the condenser will result in pre
mature failure of the compressor.
This bath has been equipped with a brownout and over voltage protection
•
device as a safety feature to protect the system components.
Mode of Operation: This bath needs to be plugged into the line voltage
•
for at least 2 minutes before operation. This is only necessary for the first
time that the bath is energized or when it is moved from one location to
another. Turning the bath ON or OFF does not trigger the delay.
• If a High/Low voltage condition exists for longer than 5 seconds, the bath
de-energizes. An amber indicator on the back panel lights when this condition exists.
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• Re-energization is automatic upon correction of the fault condition and af-
ter a delay cycle of about 2 minutes. If a fault condition exists upon application of power, the bath will not energize.
• Under and Over Voltage Protection at 115 VAC
♦
Voltage Cutout: ±12.5% (101 - 129 VAC)
♦
Voltage Cut In: ±7.5% (106 - 124 VAC)
•
Under and Over Voltage Protection at 230 VAC
♦
Voltage Cutout: ±12.5% (203 - 257 VAC)
♦
Voltage Cut In: ±7.5% (213 - 247 VAC)
1.3 Authorized Service Centers
Please contact one of the following authorized Service Centers to coordinate
service on your Hart product:
Fluke Corporation, Hart Scientific Division
799 E. Utah Valley Drive
American Fork, UT 84003-9775
USA
Phone: +1.801.763.1600
Telefax: +1.801.763.1010
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7312 TPW Maintenance Bath
User’s Guide
E-mail: support@hartscientific.com
Fluke Nederland B.V.
Customer Support Services
Science Park Eindhoven 5108
5692 EC Son
NETHERLANDS
Phone: +31-402-675300
Telefax: +31-402-675321
E-mail: ServiceDesk@fluke.nl
Fluke Int'l Corporation
Service Center - Instrimpex
Room 2301 Sciteck Tower
22 Jianguomenwai Dajie
Chao Yang District
Beijing 100004, PRC
CHINA
Phone: +86-10-6-512-3436
Telefax: +86-10-6-512-3437
E-mail: xingye.han@fluke.com.cn
Fluke South East Asia Pte Ltd.
Fluke ASEAN Regional Office
Service Center
60 Alexandra Terrace #03-16
The Comtech (Lobby D)
118502
SINGAPORE
Phone: +65 6799-5588
Telefax: +65 6799-5588
E-mail: antng@singa.fluke.com
When contacting these Service Centers for support, please have the following
information available:
•
Model Number
6
Page 15
Serial Number
•
Voltage
•
Complete description of the problem
•
1 Before You Start
Authorized Service Centers
7
Page 16
2 Introduction
The Hart Scientific Model 7312 is a floor standing constant temperature bath.
This bath is useful in maintaining up to two triple point of water cells, perform
ing temperature calibration, and other applications requiring stable tempera
tures. An innovative state of the art solid-state temperature controller has been
incorporated which maintains the bath temperature with extreme stability. The
temperature controller uses a micro controller to execute the many operating
functions.
User interface is provided by the 8-digit LED display and four key-switches.
Digital remote communications is standard with an RS-232 serial interface and
optional with an IEEE-488 interface.
Temperature cutouts protect triple point of water cells from freezing or high
temperatures due to system failure. Separate circuits cut off heating or refrigeration independent of the temperature controller.
This bath was designed to be compact and low cost without compromising performance. The bath operates over a wide temperature range from –5°C to
110°C. The refrigeration permits sub-ambient temperature control.
2 Introduction
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Page 17
3 Specifications and Environment Conditions
3 Specifications and Environment
Conditions
3.1 Specifications
Range –5°C to 110°C
Stability ±0.001°C at 0°C (alcohol-water mix)
±0.004°C at 30°C (alcohol-water mix)
Uniformity ±0.003°C at 0°C (alcohol-water mix)
±0.006°C at 30°C (alcohol-water mix)
TPW Duration Six weeks, typical (assumes correctly formed ice mantle)
Set-Point Accuracy ±0.05°C at 0°C
Set-Point Repeatability ±0.01°C
Display Resolution ±0.01°C
Set-Point Resolution ±0.002°C; 0.00003°C in high-resolution mode
Access Opening 4.75” x 3.8”
(121 x 97 mm)
Specifications
Immersion Depth 19.5” (496 mm)
Volume 5 gallons (19 liters)
Power 115 VAC (±10%), 60 Hz or
230 VAC (±10%), 50 Hz
Size 12” W x 24.5” W x 32.25” H (305 x 622 x 819 mm)
Weight 75 lb. (34 kg)
Automation Package Interface-itsoftware and an RS-232 computer interface are available
for setting the bath temperature via an external computer. For
IEEE-488, add 2001-IEEE to the automation package.
Safety OVERVOLTAGE (Installation) CATEGORY II, Pollution Degree 2 per
IEC1010-1
3.2 Environmental Conditions
Although the instrument has been designed for optimum durability and trou
ble-free operation, it must be handled with care. The instrument should not be
operated in an excessively dusty or dirty environment. Maintenance and clean
ing recommendations can be found in the Maintenance section of this manual.
The instrument operates safely under the following conditions:
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-
•
temperature range: 5-35°C (41-95°F)
•
ambient relative humidity: maximum 80% for temperature <31°C, de
creasing linearly to 50% at 40°C
•
pressure: 75kPa – 106kPa
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4 Quick Start
CAUTION: Read Section 6 entitled BATH USE before placing the bath in
service.
This chapter gives a brief summary of the steps required to set up and operate
the bath. This should be used as a general overview and reference and not as a
substitute for the remainder of the manual. Please read Section 6, Installation,
through Section 9, General Operation, carefully before operating the bath.
4.1 Unpacking
4 Quick Start
Unpacking
Unpack the bath carefully and inspect it for any damage that may have oc
curred during shipment. If there is shipping damage, notify the carrier immediately. Verify that all components are present:
• 7312 Bath
• Access Hole Cover and Components.
• Triple Point of Water Support Racks and Adapters.
• User’s Guide
• Report of Test
• Drain Valve
If you are missing any item, please call an Authorized Service Center for
assistance.
4.2 Set Up
CAUTION: The drain valve must be installed on the back of the bath be
fore attempting to fill the tank with fluid. See Section 5.3, on page 17 for
drain installation instructions.
-
-
WARNING: The instrument is equipped with a soft cutout (user settable
firmware) and a hard cutout (set at the factory). Check the flash point,
boiling point, or other fluid characteristic applicable to the circumstances
of the unit operation. Ensure that the soft cutout is adjusted to the fluid
characteristics of the application. As a guideline, the soft cutout should be
set 10°C to 15°C below the flash point of the bath fluid. See Section 8.1,
Heat Transfer Fluid, for specific information on bath fluids and Section
9.8, Cutout.
Set up of the bath requires careful unpacking and placement of the bath, filling
the bath with fluid, and connecting power. Consult Section 6, Installation, for
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7312 TPW Maintenance Bath
User’s Guide
detailed instructions for proper installation of the bath. Be sure to place the
bath in a safe, clean and level location.
Fill the bath tank with an appropriate liquid. For operation at moderate bath
temperatures, clean distilled water works well above 0°C and below 70°C.
Carefully pour the fluid into the bath tank through the large rectangular access
hole above the tank avoiding spilling any fluid. The fluid must not exceed a
height of 12.7-20.3 mm (0.5-0.8 inches) below the bottom of the lid (NOT the
access cover).
4.3 Power
Plug the bath power cord into a mains outlet of the proper voltage, frequency
and current capability. Refer to Section 3.1, Specifications, for power details.
Refer to and read the caution at the front of the manual concerning brownout
and over voltage protection. Check the back panel label for the correct voltage
and frequency prior to energizing the unit. Turn the bath on using the front
panel “POWER” switch. The baths turns on and begins to heat or cool to reach
the previously programmed temperature set-point. The front panel LED display
indicates the actual bath temperature. Set the cooling switch to “OFF” for temperature above approximately 45°C. Set the switch to “ON” for lower
temperatures.
4.4 Setting the Temperature
In the following discussion and throughout this manual a solid box around the
word SET, UP, DOWN, or EXIT. Indicates the panel button to press while the
dotted box indicates the display reading on the front panel. Explanation of the
button function or display reading is written at the right.
To view or set the bath temperature set-point proceed as follows. The front
panel LED display normally shows the actual bath temperature.
24.68 C Bath temperature display
When the “SET” button is pressed the display shows the set-point memory that
is currently being used and its value. Eight set-point memories are available.
S
Set-point 1, 25.0°C currently used
Press the “SET” button to select this memory and access the set-point value.
S
Access set-point selection.
Access set-point value
14
C 25.00 Current value of set-point 1, 25.00°C
Press the “UP” or “DOWN” button to change the set-point value.
Page 21
4 Quick Start
Setting the Temperature
U
Increment display
C 30.00 New set-point value
Press the “SET” button to accept the new value and to display the vernier value.
The bath begins heating or cooling to the new set-point.
S
Store new set-point, access vernier
0.00000 Current vernier value
Press the “EXIT” button and the bath temperature is displayed again.
E
Return to the temperature display
24.73 C Bath temperature display
The bath heats or cools until it reaches the new set-point temperature. Turn off
the cooling to reach and control at higher temperatures.
When setting the set-point temperature be careful not to exceed the temperature
limit of the bath fluid. The over-temperature cutout should be correctly set for
added safety. See Section 9.8, Cutout.
To obtain optimum control stability adjust the proportional band as discussed in
Section 9.7, Proportional Band.
15
Page 22
5 Installation
CAUTION: Read Section 6 entitled BATH USE before placing the bath
into service.
5.1 Bath Environment
The Model 7312 Bath is a precision instrument, which should be located in an
appropriate environment. The location should be free of drafts, extreme temper
atures and temperature changes, dirt, etc. The surface where the bath is placed
must be level. Allow plenty of space around the bath for air circulation.
The top surface of the bath may become hot at high temperatures. Beware of
the danger of accidental fluid spills.
A fume hood should be used to remove any vapors given off by hot bath fluid.
5 Installation
Bath Environment
-
5.2 “Dry-out” Period
Before initial use, after transport, and any time the instrument has not been energized for more than 10 days, the bath needs to be energized for a “dry-out”
period of 1-2 hours before it can be assumed to meet all of the safety requirements of the IEC 1010-1.
5.3 Bath Preparation and Filling
CAUTION: Before filling the tank with fluid the drain valve must be installed onto the pipe fitting at the back of the bath.
5.3.1 Drain Valve Installation Instructions
The drain valve attaches to the swage fitting located on the lower backside of
the bath. (See Figure 1.)
1. Place the valve onto the drain fitting and hand tighten in place by turning
the hex nut (attached to the bath) counter clockwise while holding the
valve stationary.
2. Using open-end wrenches, hold the valve in place and tighten the hex
nub one quarter turn from the hand tightened position above.
The valve should be secured in place at this point. If not, repeat step number 2
being careful not to over tighten the assembly.
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7312 TPW Maintenance Bath
User’s Guide
Ensure the valve handle is in the closed position before attempting to add fluid
to the tank.
Hex Nut
Back of bath
Figure 1 Drain Valve Installation—IMPORTANT: Do Not Over
Tighten. Follow the installation instructions above.
Valve body
5.3.2 Filling With Fluid
The Model 7312 Bath is not provided with a fluid. Various fluids are available
from Hart Scientific and other sources. Depending on the desired temperature
range, any of the following fluids, as well as others, may be used in the bath:
•
Water
•
Ethylene glycol/water
•
Mineral oil
•
Silicone oil
Fluids are discussed in detail in Section 9.1, Heat Transfer Fluid.
18
Remove any access hole cover from the bath and check the tank for foreign
matter (dirt, remnant packing materials, etc.).
Fill the bath with clean unpolluted fluid. Fill the bath carefully through the
large rectangular access hole to a level that allows for stirring and thermal ex
pansion. Section 9.1.5, Thermal Expansion, explains fluid expansion. DO NOT
turn on the bath without fluid in the tank. Maximum and minimum fill levels
are dependent on the application whether it is used for TPW cells or compari
son calibration. Carefully monitor the bath fluid level as the bath temperature
rises to prevent overflow or splashing. Remove excess hot fluid if necessary
with caution.
Page 24
5.4 Power
With the bath power switch off, plug the bath into an AC mains outlet of the
appropriate voltage, frequency, and current capacity. Refer to Section 3.1,
Specifications, for power details. Refer to and read the caution at the front of
the manual concerning brownout and over voltage protection. Check the back
panel label for the correct voltage and frequency prior to energizing the unit.
5 Installation
Power
19
Page 25
6 Bath Use
CAUTION: Read this section entitled BATH USE before placing the bath
in service.
6 Bath Use
General
The information in this section is for general information only. It is not de
signed to be the basis for calibration laboratory procedures. Each laboratory
needs to write their specific procedures. Some of the information in this text
may not apply to the specific bath you have purchased.
6.1 General
Be sure to select the correct fluid for the temperature range of the calibration.
Bath fluids should be selected to operate safely with adequate thermal proper
ties to meet the application requirements. Also, be aware that fluids expand
when heated and could overflow the bath if not watched. Refer to General Op
eration, Section 9, for information specific to fluid selection and to the MSDS
sheet specific to the fluid selected. Generally, baths are set to one temperature
and used to calibrate probes only at that single temperature. This means that the
type of bath fluid does not have to change. Additionally, the bath can be left energized reducing the stress on the system.
The bath generates extreme temperatures. Precautions must be taken to prevent
personal injury or damage to objects. Probes may be extremely hot or cold
when removed from the bath. Cautiously handle probes to prevent personal injury. Carefully place probes on a heat/cold resistant surface or rack until they
are at room temperature. It is advisable to wipe the probe with a clean soft cloth
or paper towel before inserting it into another bath. This prevents the mixing of
fluids from one bath to another. If the probe has been calibrated in liquid salt,
carefully wash the probe in warm water and dry completely before transferring
it to another fluid. Always be sure that the probe is completely dry before in
serting it into a hot fluid. Some of the high temperature fluids react violently to
water or other liquid mediums. Be aware that cleaning the probe can be danger
ous if the probe has not cooled to room temperature. Additionally, high temper
ature fluids may ignite the paper towels if the probe has not been cooled.
-
-
-
-
-
-
For optimum accuracy and stability, allow the bath adequate stabilization time
after reaching the set-point temperature.
6.2 Triple Point of Water Cell Maintenance
6.2.1 Bath Preparation
The bath fluid to maintain the TPW cell must be able to operate near 0°C with
out freezing. Water alone can freeze. Water with about 10% ethanol is a good
fluid for this application. It retains most of the excellent temperature control
properties of water while reducing the freezing point to a useable level. The
-
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7312 TPW Maintenance Bath
User’s Guide
mixture is also inexpensive and not flammable. Pure denatured ethanol or other
alcohols may be used directly but they can pose a fire hazard. Ethylene glycol
is not recommended because it leaves a sticky residue requiring cleaning of the
thermometers immersed into it.
Be sure the over-temperature and the water triple point cutouts are properly set.
See Sections 10.8 and 10.11.2.
6.2.2 Setting the Bath Temperature
The actual bath temperature must be from 0.007 to 0.008°C. Use an accurate
thermometer capable of reading to three decimal places to set the temperature.
While the bath may be calibrated to an extent (see Section 12), the set-point ac
curacy by itself is not sufficient. Check the reference thermometer against the
TPW to assure accuracy of the temperature setting. The resolution of the digital
temperature setting is to 0.002 °C. The set-point vernier feature of the temperature controller (see Section 10.3.3) is helpful here. The temperature of the bath
needs to be checked occasionally over the first hour to ensure that control at the
required temperature is established. Check the bath temperature occasionally
over a few weeks to verify that it has not drifted as well.
-
The condition of the ice mantle must be monitored regularly. If the mantle
seems to be growing, increase the temperature. Likewise, if the ice mantle
seems to be melting back, lower the temperature.
6.2.3 Adjusting the TPW Cell Rack
The 7312 bath is provided with two adjustable racks that provide stable location for the cells. See Figure 2. Remove the racks by reaching in and withdrawing them. The stainless steel baffles on the left and right sides of the tank act as
guides or tracks to locate and retain each rack. A TPW rack consists of support
rods, a bottom plate and a top plate. The support plates are positioned on the
support rods with set screws. Each plate is individually adjusted in order to adjust cell depth and to adjust cell fit. Start by adjusting the bottom plates until
the cell is at the proper height. Rubber grommets protect the cell surfaces from
direct contact with the metal. The top plate is sufficiently large for the Hart Sci
entific Model 5901 cell. Adapters are provided for each rack to fit the Hart
TPW cells and most other commercially available cells. Other adapters are
available upon request.
6.2.4 Fluid Level
The bath fluid level may be adjusted as desired for the cells. Typically the fluid
level for the Hart Scientific Model 5901 cell is below the funnel but above the
top end bell of the cell. The Hart Scientific Model 5901A cell fluid level may
be just under or just over the opening. Use the adjustability of the racks to com
pensate for different cell designs. See the Figure 3. The handles of the NBS
style cells (Hart Model 5901A) are as shown in Figure 4.
-
-
22
Page 27
Removable
Guide Tubes
6 Bath Use
Triple Point of Water Cell Maintenance
Rubber Shock Guides
Thermometer Precooling Holes
Access Cover
Adapter
Top Plate
Support Rods
Guide Location
Adjusting
Set Screws
TPW Cells
Baffle
Rubber
Grommet
Bottom Plate
Figure 2 Details of the Access Cover and Cell Racks
Guide Location
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7312 TPW Maintenance Bath
User’s Guide
Adjusting the fluid level so that the top bell is exposed permits added heat input
to the cell causing the top of the ice mantle to melt. Careful adjustment can ad
equately maintain the cell while reducing the ice bridging at the top of the cell.
The fluid and fluid level should be regularly checked. If a second cell is added
or removed for a prolonged period adjust the fluid level appropriately. Keep the
fluid clean. Verify that there is no ice formation on the sides in the lower half of
the tank. Formation of ice indicates insufficient alcohol in the water.
6.2.5 Features of the Bath Access Cover
The bath access cover fits over the opening of the bath providing a barrier
against the ambient temperature while providing holes for immersion of ther
mometers. Remove the cover to maintain the cells and bath fluid. Normally the
cover must be on. See Figure 2.
The four wells toward the rear of the cover are used for pre-cooling thermometers of typical SPRT size and smaller diameter. Pre-cool each thermometer to
the bath temperature in order to prevent melting the ice mantle in the TPW cell.
Melting the mantle reduces its lifetime requiring it to be refrozen sooner. Each
well has a rubber shock guide at the top to help reduce shock (strain) to the delicate platinum sensor in an SPRT. Underneath the cover, a guide tube helps to
prevent the thermometer from contacting internal parts. If the thermometer is
longer than 20 inches, the user must retain it to prevent it from striking the
bottom.
-
-
The two wells in the front permit thermometers to gain access to the TPW cells.
They also feature the rubber shock guide and guide tube. The shock guide and
guide tube are removable as an assembly to permit shorter thermometers to be
more fully immersed into the cell.
6.2.6 Maintenance of the TPW Cell
The TPW cells may be maintained for days to months depending upon care and
maintenance and usage of the cell. The following steps are typical.
1. Set up the bath and cells as described above.
2. Pre-cool the cell to the bath temperature prior to freezing the mantle.
3. Freeze the cell according to the manufacturers instructions.
4. Fill the reentrant tube of the cell with chilled bath fluid to a level suffi
cient to reach the cells water level when a thermometer is inserted.
5. Insert the cell carefully into the bath. Be certain that bottom of the cell is
seated on the bottom plate grommet.
6. Verify the bath fluid level is adequate.
The cell may be held in the bath for many weeks if the daily maintenance is
properly kept up. The daily maintenance consists of the following:
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24
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6 Bath Use
Triple Point of Water Cell Maintenance
Fluid Level
in Bath
Figure 3 Fluid Level
25
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7312 TPW Maintenance Bath
User’s Guide
Figure 4 Location of Handles for NBS Design Cells
• Check for ice bridging every 1 to 3 days as required. Ice bridging is ice
forming at the top surface of the water in the cell that bridges from the
reentrant tube to the outer glass wall. Ice bridging can cause a cell to be
broken. It must be melted back regularly.
CAUTION: Wipe bath fluid off the cell as it is removed to prevent fluid
from running onto the bath controller.
•
Check the ice mantle to see if it is free from the reentrant tube perhaps
several times a day depending upon use. This freedom of movement
means that there is a thin layer of water all around the reentrant tube. If it
is not free to move, small errors result in the acquired temperature. Insert
a room temperature rod into the fluid in the reentrant tube transferring
heat to the ice until the mantle moves freely. This movement can be
checked by rotating the cell quickly around its long axis. The ice tends to
stay in place as the cell rotates if it is free.
•
Make fine adjustments as needed to the bath set-point temperature to in
sure that the cell mantle is neither freezing nor melting inappropriately.
-
26
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6.3 Comparison Calibration
Comparison calibration involves testing a probe (unit under test, UUT) against
a reference probe. After inserting the probes to be calibrated into the bath, al
low sufficient time for the probes to settle and the temperature of the bath to
stabilize.
6 Bath Use
Comparison Calibration
-
One of the significant dividends of using a bath rather than a dry-well to cali
brate multiple probes is that the probes do not need to be identical in construc
tion. The fluid in the bath allows different types of probes to be calibrated at
the same time. However, stem effect from different types of probes is not to
tally eliminated. Even though all baths have horizontal and vertical gradients,
these gradients are minimized inside the bath work area. Nevertheless, probes
should be inserted to the same depth in the bath liquid. Be sure that all probes
are inserted deep enough to prevent stem effect. From research at Hart Scien
tific, we suggest a general rule-of-thumb for immersion depth to reduce the
stem effect to a minimum: 20 x the diameter of the UUT + the sensor length.
Do not submerge the probe handles. If the probe handles get too warm during
calibration at high temperatures, a heat shield could be used just below the
probe handle. This heat shield could be as simple as aluminum foil slid over the
probe before inserting it in the bath or as complicated as a specially designed
reflective metal apparatus.
When calibrating over a wide temperature range, starting at the highest temperature and progressing down to the lowest temperature can generally achieve
better results.
Probes can be held in place in the bath by using probe clamps or drilling holes
in the access cover. Other fixtures to hold the probes can be designed. The object is to keep the reference probe and the probe(s) to be calibrated as closely
grouped as possible in the working area of the bath. Bath stability is maximized
when the bath working area is kept covered.
-
-
-
-
In preparing to use the bath for calibration start by:
•
Placing the reference probe in the bath working area.
•
Placing the probe to be calibrated, the UUT, in the bath working area as
close as feasibly possible to the reference probe.
6.4 Calibration of Multiple Probes
Fully loading the bath with probes increases the time required for the tempera
ture to stabilize after inserting the probes. Using the reference probe as the
guide ensures that the temperature has stabilized before starting the calibration.
-
27
Page 32
7 Parts and Controls
7.1 Front Panel
The following controls and indicators are present on the controller front panel
(see Figure 5 below): (1) the digital LED display, (2) the control buttons, (3)
the bath on/off power switch, (4) the control indicator light, and (5) the cooling
on/off switch.
7 Parts and Controls
Front Panel
Figure 5 Front Controller Panel
1. The digital display is an important part of the temperature controller. It displays the set-point temperature and bath temperature as well as the various
other bath functions, settings, and constants. The display shows the temperatures according to the selected scale units °C or °F.
2. The control buttons (SET, DOWN, UP, and EXIT) are used to set the bath
temperature set-point, access and set other operating parameters, and access
and set bath calibration parameters. A brief description of the functions of the
buttons follows:
SET – Used to display the n ext parameter in a menu and to set parameters to
the displayed value.
DOWN – Used to decrement the displayed value of parameters.
UP – Used to increment the displayed value.
EXIT – Used to exit from a menu. When the EXIT button is pressed any
changes made to the displayed value are ignored.
3. The on/off switch controls power to the entire bath including the stirring
motor.
4. The control indicator is a two color light emitting diode (LED). This indicator lets the user visually see the ratio of heating to cooling. When the indicator
is red the heater is on, and when it is green the heater is off and the bath is
cooling.
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7312 TPW Maintenance Bath
User’s Guide
5. The cooling on/off switch turns on the refrigeration for control below 50°C
and rapid cool down.
7.2 Bath Tank and Lid
The bath tank and lid assembly includes: the tank, the control probe, the stir
ring motor, the access hole, and the access hole cover. The stirring motor cover
covers the stirring motor, cooling fan, control probe, and triple point of water
cutout probe.
The bath tank is constructed of stainless steel. It is very resistant to oxida
•
tion in the presence of most chemicals and over a wide range of tempera
tures.
The control probe provides the temperature feedback signal to the con
•
troller allowing the controller to maintain a constant temperature. The
control probe is a precision platinum resistance thermometer (PRT). It is
delicate and must be handled carefully. The probe is placed in the small
hole in the top of the bath so that the probe tip is fully immersed in the
bath fluid.
• The triple point of water cutout probe senses bath temperature and acti-
vates the low temperature cutout to turn off the refrigeration below a preset temperature in case of temperature controller failure. This feature is
intended to protect triple point of water cells.
• The stirring motor is mounted on the bath tank lid. It drives the stirring
propeller to provide mixing of the bath fluid. Proper mixing of the fluid is
important for good constant temperature stability.
-
-
-
-
• The large access hole on the bath lid is used for filling and emptying the
bath with fluids and for placement of thermometers, TPW cells, and other
devices into the bath.
• An access hole cover should be used to cover the access opening in the
top of the bath. This improves bath temperature stability, prevents excess
fluid evaporation or fumes and increases safety with hot fluid. The triple
point of water cell maintenance access cover provides thermometer wells
for precooling and access to the TPW cells. See Section 6.2.6 Mainte
nance of the TPW Cell.
7.3 Back Panel
On the back of the bath are the system fuses, removable power cord, high-low
voltage indicator, drain, serial port, and IEEE-488 port (if installed).
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Page 34
8 General Operation
8.1 Heat Transfer Fluid
Many fluids work with 7312 bath. Choosing a fluid requires consideration of
many important characteristics of the fluid. Among these are temperature
range, viscosity, specific heat, thermal conductivity, thermal expansion, electri
cal resistivity, fluid lifetime, safety, and cost.
8.1.1 Temperature Range
One of the most important characteristics to consider is the temperature range
of the fluid. Few fluids work well throughout the entire temperature range of
the bath. The temperature at which the bath is operated must always be within
the safe and useful temperature range of the fluid used. The lower temperature
range of the fluid is determined either by the freeze point of the fluid or the
temperature at which the viscosity becomes too great. The upper temperature is
usually limited by vaporization, flammability, or chemical breakdown of the
fluid. Vaporization of the fluid at higher temperatures may adversely affect
temperature stability because of cool condensed fluid dripping into the bath
from the lid.
8 General Operation
Heat Transfer Fluid
-
The bath temperature should be limited by setting the safety cutout so that the
bath temperature cannot exceed the safe operating temperature limit of the
fluid.
8.1.2 Viscosity
Viscosity is a measure of the thickness of a fluid or how easily it can be poured
and mixed. Viscosity affects the temperature uniformity and stability of the
bath. With lower viscosity fluid mixing is better creating a more uniform temperature throughout the bath. This improves the bath response time allowing it
to maintain a more constant temperature. For good control the viscosity should
be less than 10 centistokes. Fifty centistokes is about the practical upper limit
of allowable viscosity. Viscosity greater than this causes very poor control sta
bility because of poor stirring and may also overheat or damage the stirring mo
tor. Viscosity may vary greatly with temperature, especially with oils.
When using fluids with higher viscosities the controller proportional band may
need to be increased to compensate for the reduced response time. Otherwise
the temperature may begin to oscillate.
8.1.3 Specific Heat
Specific heat is the measure of the heat storage ability of the fluid. Specific
heat, to a small degree, affects the control stability. It also affects the heating
and cooling rates. Generally, a lower specific heat means quicker heating and
cooling. The proportional band may require some adjustment depending on the
specific heat of the fluid.
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8.1.4 Thermal Conductivity
Thermal conductivity measures how easily heat flows through the fluid. Ther
mal conductivity of the fluid affects the control stability, temperature unifor
mity, and temperature settling time. Fluids with higher conductivity distribute
heat more quickly and evenly improving bath performance.
8.1.5 Thermal Expansion
Thermal expansion describes how much the volume of the fluid changes with
temperature. Thermal expansion of the fluid must be considered since the in
crease in fluid volume as the bath temperature increases may cause overflow. It
may be dangerous to permit the fluid to overflow the tank. It may also cause
loss of valuable bath fluid. Excessive thermal expansion may also be undesir
able in applications where constant liquid level is important.
Thermal expansion coefficients of several fluids are shown in Table 2, Table of
Bath Fluids. Fluid manufacturers can also provide this information. The thermal expansion coefficients are shown in units of cm/cm/°C, however, the values
are the same for any units of length. Divide the value by 1.8 for °F coefficients.
The following equation may be used to find the desired depth:
De = Ds [K(Te-Ts)+1]
Or
-
-
-
-
Ds = De/[K(Te-Ts)+1] where De < or = The Maximum Fill Depth
Where:
K=Expansion coefficient
Te=Ending Temperature
Ts=Starting Temperature
De=Ending Depth
Ds=Starting Depth
The maximum fill depth is typically 0.5 to 0.8 inches below the level of the
gasket at the top of the bath tank (not the top of the bath lid). Judgment must be
made with different stirring arrangements to prevent splashing on the gasket or
lid of the bath.
Example:
The final depth of Dow Corning 710 silicone oil in the bath tank is to be 9.2
inches when heated from 25 to 300°C. What should the starting depth be?
Expansion coefficient for 710 oil on Table 2, K=0.00077 inch/inch/°C
Ending temperature, Te=300°C
32
Starting temperature, Ts=25°C
Ending depth, De=9.2 inches
Page 36
Ds=9.2/[0.00077 (300-25) + 1] = 7.59 inches
8.1.6 Electrical Resistivity
Electrical resistivity describes how well the fluid insulates against the flow of
electric current. In some applications, such as measuring the resistance of bare
temperature sensors, it may be important that little or no electrical leakage oc
cur through the fluid. In such conditions choose a fluid with very high electri
cal resistivity.
8.1.7 Fluid Lifetime
8 General Operation
Heat Transfer Fluid
-
-
Many fluids degrade over time because of vaporization, water absorption, gel
ling, or chemical breakdown. Often the degradation becomes significant near
the upper temperature limit of the fluid, substantially reducing the fluid’s
lifetime.
8.1.8 Safety
When choosing a fluid always consider the safety issues associated. Obviously
where there are extreme temperatures there can be danger to personnel and
equipment. Fluids may also be hazardous for other reasons. Some fluids may
be considered toxic. Contact with eyes, skin, or inhalation of vapors may cause
injury. A proper fume hood must be used if hazardous or bothersome vapors
are produced.
WARNING: Fluids at high temperatures may pose danger from BURNS,
FIRE, and TOXIC FUMES. Use appropriate caution and safety equipment.
Fluids may be flammable and require special fire safety equipment and procedures. An important characteristic of the fluid to consider is the flash point. The
flash point is the temperature at which there is sufficient vapor given off so that
when there is adequate oxygen present and an ignition source is applied the va
por ignites. This does not necessarily mean that fire is sustained at the flash
point. The flash point may be either of the open cup or closed cup type. Either
condition may occur in a bath situation. The open cup flash point is measured
under the condition of vapors escaping the tank. The closed cup flash point is
measured with the vapors being contained within the tank. Since oxygen and an
ignition source is less available inside the tank the closed cup flash point is
lower than the open cup flash point.
-
-
Environmentally hazardous fluids require special disposal according to applica
ble federal or local laws after use.
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7312 TPW Maintenance Bath
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8.1.9 Cost
Cost of bath fluids may vary greatly, from cents per gallon for water to hun
dreds of dollars per gallon for synthetic oils. Cost may be an important consid
eration when choosing a fluid.
8.1.10 Commonly Used Fluids
Below is a description of some of the more commonly used fluids and their
characteristics.
8.1.10.1 Water
Water is often used because of its very low cost, its availability, and its excel
lent temperature control characteristics. Water has a very low viscosity and
good thermal conductivity and heat capacity, which make it among the best flu
ids for good control stability at lower temperatures. Temperature stability is
much poorer at higher temperatures because water condenses on the lid, cools
and drips into the bath. Water is safe and relatively inert. The electrical conduc
tivity of water may prevent its use in some applications. Water has a limited
temperature range, from a few degrees above 0°C to a few degrees below
100°C. At higher temperatures evaporation becomes significant. Water used in
the bath should be distilled or deionized to prevent mineral deposits. Consider
using an algaecide chemical in the water to prevent contamination.
-
-
-
-
-
8.1.10.2 Ethylene Glycol
The temperature range of water may be extended by using a solution of one
part water and one part ethylene glycol (antifreeze). The characteristics of the
ethylene glycol-water solution are similar to water but with higher viscosity.
Use caution with ethylene glycol since this fluid is very toxic. Ethylene glycol
must be disposed of properly.
8.1.10.3 Mineral Oil
Mineral oil or paraffin oil is often used at moderate temperatures above the
range of water. Mineral oil is relatively inexpensive. At lower temperatures
mineral oil is quite viscous and control may be poor. At higher temperatures
vapor emission becomes significant. The vapors may be dangerous and a fume
hood should be used. As with most oils mineral oil expands as temperature in
creases so be careful not to fill the bath too full that it overflows when heated.
The viscosity and thermal characteristics of mineral oil is poorer than water so
temperature stability is not as good. Mineral oil has very low electrical conduc
tivity. Use caution with mineral oil since it is flammable and may also cause se
rious injury if inhaled or ingested.
8.1.10.4 Silicone Oil
-
-
-
34
Silicone oils are available which offer a much wider operating temperature
range than mineral oil. Like most oils, silicone oils have temperature control
Page 38
characteristics, which are somewhat poorer than water. The viscosity changes
significantly with temperature and also causes thermal expansion to occur.
These oils have very high electrical resistivity. Silicone oils are fairly safe and
non-toxic. Silicone oils are fairly expensive.
8.1.11 Fluid Characteristics Charts
Table 2 and Figure 6 on pages 36 and 37 have been created to provide help in
selecting a heat exchange fluid media for your constant temperature bath.
These charts provide both a visual and numerical representation of most of the
physical qualities important in making a selection. The list is not all inclusive.
There may be other useful fluids not shown in this listing. The charts include
information on a variety of fluids, which are often used as heat transfer fluid in
baths. Because of the temperature range some fluids may not be useful with
your bath.
8.1.11.1 Limitations and Disclaimer
The information given in this manual regarding fluids is intended to be used as
a general guide in choosing a fluid. Though every effort has been made to provide correct information we cannot guarantee accuracy of data or assure suitability of a fluid for a particular application. Specifications may change and
sources sometimes offer differing information. Hart Scientific cannot be liable
for any personal injury or damage to equipment, product or facilities resulting
from the use of these fluids. The user of the bath is responsible for collecting
correct information, exercising proper judgment, and insuring safe operation.
Operating near the limits of certain properties such as the flash point or viscosity can compromise safety or performance. Your company’s safety policies regarding flash points, toxicity, and such issues must be considered. You are
responsible for reading the MSDS (material safety data sheets) and acting
accordingly.
8 General Operation
Heat Transfer Fluid
8.1.11.2 About the Graph
The fluid graph visually illustrates some of the important qualities of the fluids
shown.
Temperature Range: The temperature scale is shown in degrees Celsius. The
shaded bands indicate the fluids’ general range of application. Qualities includ
ing pour point, freeze point, important viscosity points, flash point, boiling
point and others may be shown.
Freezing Point: The freezing point of a fluid is an obvious limitation to stir
ring. As the freezing point is approached high viscosity may also limit
performance.
Fume Point: The point at which a fume hood should be used. This point is
very subjective in nature and is impacted by individual tolerance to different
fumes and smells, how well the bath is covered, the surface area of the fluid in
the bath, the size and ventilation of the facility where the bath is located and
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35
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7312 TPW Maintenance Bath
User’s Guide
Table 2 Table of Various Bath Fluids and Their Properties
Lower
Fluid
(# = Hart Part No.)
Halocarbon 0.8
#5019
Methanol –96°C (fr) 10°C (fl,cc) 12°C 1.3 @ –35°C
Water 0°C (fr) 95°C (b) NONE 1 @ 25°C
Ethylene
Glycol—50% #5020
Mineral Oil No.7
#5011
Silicone Oil Type
200.05 #5010
Silicone Oil Type
200.10 #5012
Silicone Oil Type
200.20 #5013
Silicone Oil Type
200.50 #5014
Silicone Oil Type
550 #5016
Silicone Oil Type
710 #5017
Silicone Oil Type
210-H
Heat Transfer Salt
#5001
*Limiting Factors — b - boiling point e - high evaporation fl - flash point fr - freeze point v - viscosity — Flash point test oc = open cup cc = closed cup
**Very low water solubility, ice will form as a slush from condensation below freezing.
Temperature
Limit*
–100°C (v)** 70°C (e) NONE 5.7 @ –50°C
–30°C (fr) 90°C (b) NONE 7 @ 0°C
10°C (v) 166°C (fl) 168°C 15 @ 75°C
–40°C (v)** 130°C (fl, cc) 133°C 5 @ 25°C 0.92 @ 25°C 0.4 0.00028 @ 25°C 0.00105 1000 @ 25°C
–30°C (v)** 209°C (fl, cc) 211°C 10 @ 25°C
10°C (v) 230°C (fl, cc) 232°C 20 @ 25°C 0.949 @ 25°C 0.370 @ 40°C
30°C (v) 278°C (fl, cc) 280°C 50 @ 25°C 0.96 @ 25°C 0.4 0.00037 @ 25°C 0.00104 1000 @ 25°C
70°C (v) 230°C (fl, cc)
80°C (v) 300°C (fl, oc) 302°C 50 @ 80°C
66°C (v) 313°C (fl, oc) 315°C 50 @ 66°C
180°C (fr) 550°C NONE 34 @ 150°C
Upper
Temperature
Limit*
300°C (fl, oc)
Flash
Viscosity
Point
(centistokes)
0.8 @ 40°C
0.5 @ 70°C
0.66 @ 0°C
0.45 @ 20°C
0.4 @ 75°C
2 @ 50°C
0.7 @ 100°C
5 @ 125°C
3 @ 135°C
232°C 50 @ 70°C
10 @ 104°C
7 @ 204°C
14 @ 204°C
6.5 @ 300°C
2.4 @ 500°C
Specific
Gravity
1.71 @ 40°C 0.2 0.0004 0.0011
0.810 @ 0°C
0.792 @ 20°C
1.00 1.00 0.0014 0.0002 @ 25°C
1.05 0.8 @ 0°C 0.001
0.87 @ 25°C
0.84 @ 75°C
0.81 @ 125°C
0.934 @ 25°C 0.43 @ 40°C
1.07 @ 25°C 0.358 @ 40°C
1.11 @ 25°C 0.363 @ 40°C
0.96 @ 25°C 0.34 @ 100°C 0.0003 0.00095 100 @ 25°C
2.0 @ 150°C
1.9 @ 300°C
1.7 @ 500°C
Specific Heat
(cal/g/°C)
0.6 0.0005 @ 20°C 0.0014 @ 25°C
0.48 @ 25°C
0.53 @ 75°C
0.57 @ 125°C
0.45 @ 100°C
0.482 @ 200°C
0.393 @ 100°C
0.420 @ 200°C
0.386 @ 100°C
0.433 @ 200°C
0.454 @ 100°C
0.505 @ 200°C
0.33 0.0014 0.00041
Thermal
Conductivity
(cal/s/cm/°C)
0.00025 @ 25°C 0.0007 @ 50°C 5 @ 25°C
0.00032 @ 25°C 0.00108 1000 @ 25°C
0.00034 @ 25°C 0.00107 1000 @ 25°C
0.00035 @ 25°C 0.00075 100 @ 25°C
0.00035 @ 25°C 0.00077 100 @ 25°C
Thermal
Expansion
(cm/cm/°C)
Resistivity
12
(10
-cm )
10 @ 150°C
50 @ 150°C
50 @ 150°C
50 @ 150°C
1 @ 150°C
1 @ 150°C
1 @ 150°C
3
1.7
Ω
/cm
36
other conditions. We assume the bath is well covered at this point. This is also
subject to company policy.
Flash Point: The point at which ignition may occur. The point shown may be
either the open or closed cup flash point. Refer to the flash point discussion in
Section 9.1.8, Safety.
Boiling Point: At or near the boiling point of the fluid the temperature stability
is difficult to maintain. Fuming or evaporation is excessive. Large amounts of
heater power may be required because of the heat of vaporization.
Page 40
8 General Operation
Stirring
–100°C 0°C 100°C 200°C 300°C 400°C 500°C 600°C
Silicone Oil
5017
Silicone Oil
5014
Silicone Oil
5013
Silicone Oil
5012
Silicone Oil
5010
HFE 7500
5023
Halocarbon
5019
Mineral Oil
5011
Water
Methanol
Ethanol
Ethylene Glycol
(50/50 with H O)
Dynalene HF/LO
2
5020
5022
PP
PP
PP
PP
10 CS
FR (Pure)
10 CS
10 CS
FR
10 CS
FR
10 CS
FL 12°C
FL 16°C
10 CS
10 CS
10 CS
EP
10 CS
BP
FL 60°C
FL 133°C
EP 100°C
BP
BP
10 CS
10 CS
FL 302°CPP
FL 280°C
FL 232°C
FL 211°C
FL 177°C
Bath Salt
5001
FR
Legend
Shaded area represents usable range of fluid starting at
50 centistokes. Lighter shading represents decreasing
viscosity, while vaporization and decomposition increase.
Black area represents liquid range with excessive
viscosity.
Range over which a fume hood is recommended.
Figure 6 Chart of Various Bath Fluids and Their Properties
Decomposition: The temperature may reach a point at which decomposition of
the fluid begins. Further increasing the temperature may accelerate decomposi
tion to the point of danger or impracticality.
8.2 Stirring
Stirring of the bath fluid is very important for stable temperature control. The
fluid must be mixed well for good temperature uniformity and fast controller
response. The stirrer is precisely adjusted for optimum performance.
Decomposition Starts
BP - Boiling Point
CS - Centistokes
EP - Evaporation Point
(fluid loss
due to evaporation)
FL - Flash Point
FR - Freeze Point
PP - Pour Point
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7312 TPW Maintenance Bath
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8.3 Power
Power to the bath is provided by an AC mains supply. Refer to Section 3.1,
Specifications, for power details. Refer to and read the CAUTION at the front
of the manual concerning brownout and over voltage protection. Check the
back panel label for the correct voltage and frequency prior to energizing the
unit. Power to the bath passes through a filter to prevent switching spikes from
being transmitted to other equipment.
To turn on the bath, switch the control panel power switch to the ON position.
The stirring motor turns on, the LED display begins to show the bath tempera
ture, and the heater turns on or off until the bath temperature reaches the pro
grammed set-point.
When powered on, the control panel display briefly shows a four digit number.
This number indicates the number of times power has been applied to the bath.
Also briefly displayed is data, which indicates the controller hardware configuration. This data is used in some circumstances for diagnostic purposes.
-
-
8.4 Heater
The temperature controller precisely controls the bath heater to maintain a constant bath temperature. Power is controlled by periodically switching the heater
on for a certain amount of time using a solid-state relay.
The front panel red/green control indicator shows the state of the heater. The
control indicator glows red when the heater is on and glows green when the
heater is off. The indicator pulses constantly when the bath is maintaining a stable temperature.
8.5 Temperature Controller
Hart Scientific’s unique hybrid digital/analog temperature controller controls
the bath temperature. The controller offers the tight control stability of an ana
log temperature controller as well as the flexibility and programmability of a
digital controller.
The bath temperature is monitored with a platinum resistance sensor in the con
trol probe. The signal is electronically compared with the programmable refer
ence signal, amplified, and then passed to a pulse-width modulator circuit,
which controls the amount of power applied to the bath heater. The bath is op
erable within the temperature range given in the specifications. For protection
against solid-state relay failure or other circuit failure, the micro-controller au
tomatically turns off the heater with a second mechanical relay anytime the
bath temperature is more than a certain amount above the set-point temperature.
As a second protection device, the controller is also equipped with a separate
thermocouple temperature monitoring circuit, which shuts off the heater if the
temperature exceeds the cutout set-point.
-
-
-
-
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8 General Operation
Refrigeration
The controller allows the operator to set the bath temperature with high resolu
tion, set the cutout, adjust the proportional band, monitor the heater output
power, and program the controller configuration and calibration parameters.
The controller may be operated in temperature units of degrees Celsius or Fahr
enheit. The controller is operated and programmed from the front control panel
using the four key switches and digital LED display. Remote digital operation
with the controller is possible via the standard RS-232 serial port. The control
ler may be optionally equipped with an IEEE-488 GPIB digital interface. Oper
ation of the controller using the front control panel is discussed following in
Section 9, Controller Operation. Operation using the digital interface is dis
cussed in Section 10, Digital Communication Interface.
When the controller is set to a new set-point the bath heats or cools to the new
temperature. Once the new temperature is reached the bath usually takes 10-15
minutes for the temperature to settle and stabilize. There may be a small over
shoot or undershoot of about 0.5°C.
8.6 Refrigeration
Bath cooling below 50°C is provided by a compact refrigeration system. The
system utilizes the ozone safe R-134A refrigerant. The refrigerant is metered
through an automatic expansion valve to achieve bath temperatures as low as
–5°C. The evaporator and heater are sandwiched to the sides of the tank. This
provides the precision control over heat gains and losses required for high stability. The refrigeration is not required to maintain the bath above 45 to 50°C.
Continuous use of the refrigeration above 50°C will damage the compressor.
The refrigeration may be used for short periods of time for cooling down the
bath to a lower temperature. Do not exceed 60 minutes cooling above 50°C.
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-
-
-
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39
Page 43
9 Controller Operation
This chapter discusses in detail how to operate the bath temperature controller
using the front control panel. Using the front panel key switches and LED dis
play the user may monitor the bath temperature, set the temperature set-point in
degrees C or F, monitor the heater output power, adjust the controller propor
tional band, set the cutout set-point, and program the probe calibration parame
ters, operating parameters, serial and IEEE-488 interface configuration, and
controller calibration parameters. Operation is summarized in Figure 4.
9.1 Bath Temperature
The digital LED display on the front panel allows direct viewing of the actual
bath temperature. This temperature value is what is normally shown on the dis
play. The units, C or F, of the temperature value are displayed at the right. For
example,
9 Controller Operation
Bath Temperature
-
-
-
-
25.00 C Bath temperature in degrees Celsius
The temperature display function may be accessed from any other function by
pressing the “EXIT” button.
9.2 Reset Cutout
If the over-temperature cutout has been triggered, the temperature display alternately flashes.
cut-out Indicates cutout condition
The message continues to flash until the temperature is reduced and the cutout
is reset.
The cutout has two modes – automatic reset and manual reset. The mode deter
mines how the cutout is reset which allows the bath to heat up again. When in
automatic mode, the cutout resets itself as soon as the temperature is lowered
below the cutout set-point. With manual reset mode the cutout must be reset by
the operator after the temperature falls below the set-point.
When the cutout is active and the cutout mode is set to manual (“reset”), the
display flashes “cutout” until the user resets the cutout. To access the reset cut
out function, press the “SET” button.
-
-
S
The display indicates the reset function.
Access cutout reset function
RESET Cutout reset function
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7312 TPW Maintenance Bath
User’s Guide
Display
Temperature
Secondary Functions
+
SET
EXIT
SET
Display Power
SET
Set Proportional Band
EXIT
Cutout Active
Reset Cutout
SET
EXIT
EXIT
SET
EXIT
EXIT
Select Setpoint
SET
Adjust Setpoint
EXIT
Set Cutout Temp.
SET
SET
EXIT
Adjust Vernier
EXIT
SET
EXIT
Set Scale °C/°F
SET
Configuration Menu
SET
EXITEXITEXIT EXIT EXIT
Probe
Menu
SET
D0
SET SET SET
UP
DOWN
EXIT EXIT EXIT
Operating
Parameters
Menu
SET SET SET SET
Cutout
Reset Mode
SET SET
UP UP UP
DOWN DOWN DOWN
EXIT
Serial
Interface
Menu
BAUD
Rate
IEEE-488
Interface
Menu
Device
Address
Calibration
EXIT
Menu
X 5
CTO
Adj. D0
SET/EXIT SET/EXIT SET/EXIT
DG
SET
EXIT
Adj. DG
SET/EXIT
Adj. Cutout
Reset Mode
SET
Triple Point of
Water Cutout
SET
Adj. TPCO
SET
Triple Point of
Water Set-Point
SET
Adj. TPSP
SET/EXIT
EXIT
EXIT
EXIT
EXIT
Figure 7 Controller Operation Flowchart
Adjust
BAUD Rate
Sample
Period
SET
Adj. Sample
Period
SET/EXIT
Duplex
Mode
SET
Adj. Duplex
Mode
SET/EXIT
Linefeed
SET
Adjust
Linefeed
SET/EXIT
EXIT
EXIT
EXIT
Interface
Option Installed
Adj. Device
Address
SET/EXIT
IEEE-488
Option Installed
Adjust CTO
SET
Adjust H
SET/EXIT
SET
DO NOT CHANGE THESE VALUES. SEE MANUAL
Adjust L
SET/EXIT
H
EXIT
L
EXIT
42
Page 45
Press the “SET” button once more to reset the cutout.
9 Controller Operation
Temperature Set-point
S
This action also switches the display to the set temperature function. To return
to displaying the temperature, press the “EXIT” button. If the cutout is still in
the over-temperature fault condition, the display continues to flash “cutout”.
The bath temperature must drop a few degrees below the cutout set-point be
fore the cutout can be reset.
Reset cutout
9.3 Temperature Set-point
The bath temperature can be set to any value within the range and with resolu
tion as given in the specifications. The operator must know the temperature
range of the particular fluid used in the bath and the bath should only be oper
ated well below the upper temperature limit of the liquid. In addition, the cutout
temperature should also be set below the upper limit of the fluid.
Setting the bath temperature involves three steps: 1) selecting the set-point
memory, 2) adjusting the set-point value, and 3) adjusting the vernier (if
desired).
9.3.1 Programmable Set-points
-
-
-
The controller stores 8 set-point temperatures in memory. The set-points can be
quickly recalled to conveniently set the bath to a previously programmed temperature set-point.
To set the bath temperature, first select the set-point memory. This function is
accessed from the temperature display function by pressing the “SET” button.
The number of the set-point memory currently being used is shown at the left
on the display followed by the current set-point value.
25.00 C Bath temperature in degrees Celsius
S
Access set-point memory
1, 25.0 Set-point memory 1, 25.0°C currently used
To change the set-point memory press the “UP” or “DOWN” button.
U
Press the “SET” button to accept the new selection and access the set-point
value.
Increment memory
S
Accept selected set-point memory
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7312 TPW Maintenance Bath
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9.3.2 Set-point Value
The set-point value may be adjusted after selecting the set-point memory and
pressing the “SET” button. The set-point value is displayed with the units, C or
F, at the left.
C 40.00 Set-point value in °C
If the set-point value does not need to be changed, press the “EXIT” button to
resume displaying the bath temperature. Press the “UP” or “DOWN” button to
adjust the set-point value.
U
Increment display
C 42.50 New set-point value
When the desired set-point value is reached, press the “SET” button to accept
the new value and to access the set-point vernier. If the “EXIT” button is
pressed instead, any changes made to the set-point are ignored.
S
Accept new set-point value
9.3.3 Set-point Vernier
The set-point value can be set with a resolution of 0.01°C. The user may want
to adjust the set-point slightly to achieve a more precise bath temperature. The
set-point vernier allows one to adjust the temperature below or above the
set-point by a small amount with a very high resolution. Each of the eight
stored set-points has an associated vernier setting. The vernier is accessed from
the set-point by pressing the “SET” button. The vernier setting is displayed as a
six digit number with five digits after the decimal point. This is a temperature
offset in degrees of the selected units, C or F.
44
0.00000 Current vernier value in °C
To adjust the vernier, press the “UP” or “DOWN” button. Unlike most func
tions the vernier setting has immediate effect as the vernier is adjusted. The
“SET” button need not be pressed. This allows one to continually adjust the
bath temperature with the vernier as it is displayed.
4. 40.0 New set-point memory 4, 40.0°C
U
Increment display
0.00090 New vernier setting
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Page 47
9 Controller Operation
Temperature Scale Units
Next press the “EXIT” button to return to the temperature display or the “SET”
button to access the temperature scale units selection.
S
Access scale units
9.4 Temperature Scale Units
The temperature scale units of the controller may be set by the user to degrees
Celsius (°C) or Fahrenheit (°F). The units are used in displaying the bath tem
perature, set-point, vernier, proportional band, and cutout set-point.
The temperature scale units selection is accessed after the vernier adjustment
function by pressing the “SET” button. From the temperature display function,
access the units selection by pressing “SET” 4 times.
25.0 Bath temperature
S
1. 25.0 Set-point memory
S
Access et-point memory
Access set-point value
-
C 25.00 Set-point value
S
0.00000 Vernier setting
S
Un= C Scale units currently selected
Press the “UP” or “DOWN” button to change the units.
U
Un=F New units selected
Press the “SET” button to accept the new selection and resume displaying the
bath temperature.
S
Access vernier
Access scale units selection
Change units
Set the new units and resume temperature display
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7312 TPW Maintenance Bath
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9.5 Secondary Menu
Functions, which are used less often, are accessed within the secondary menu.
The secondary menu is accessed by pressing the “SET” and “EXIT” buttons si
multaneously and then releasing. The first function in the secondary menu is
the heater power display.
9.6 Heater Power
The temperature controller controls the temperature of the bath by pulsing the
heater on and off. The total power being applied to the heater is determined by
the duty cycle or the ratio of heater on time to the pulse cycle time. This value
may be estimated by watching the red/green control indicator light or read di
rectly from the digital display. By knowing the amount of heating the user can
tell if the bath is heating up to the set-point, cooling down, or controlling at a
constant temperature. Monitoring the percent heater power lets the user know
the stability of the bath. With good control stability the percent heating power
should not fluctuate more than ±1% within one minute.
-
-
The heater power display is accessed in the secondary menu. Press the “SET”
and “EXIT” button simultaneously and release. The heater power is displayed
as a percentage of full power.
S+E
Access heater power in secondary menu
12 Pct Heater power in percent
To exit out of the secondary menu, press the “EXIT” button. To continue on to
the proportional band setting, press the “SET” button.
E
Return to temperature display
9.7 Proportional Band
In a proportional controller such as this the heater output power is proportional
to the bath temperature over a limited range of temperatures around the
set-point. This range of temperature is called the proportional band. At the bot
tom of the proportional band the heater output is 100%. At the top of the pro
portional band the heater output is 0. Thus as the bath temperature rises the
heater power is reduced, which consequently tends to lower the temperature
back down. In this way the temperature is maintained at a fairly constant
temperature.
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-
46
The temperature stability of the bath depends on the width of the proportional
band (see Figure 5). If the proportional band is too wide, the bath temperature
deviates excessively from the set-point due to varying external conditions. This
is because the power output changes very little with temperature and the con
troller cannot respond very well to changing conditions or noise in the system.
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9 Controller Operation
Proportional Band
If the proportional band is too narrow the bath temperature may swing back
and forth because the controller overreacts to temperature variations. For best
control stability the proportional band must be set for the optimum width.
Proportional Band too Narrow Proportional Band too Wide
Optimum Proportional Band
Figure 8 Bath Temperature Fluctuation at Various Proportional Band Settings
The optimum proportional band width depends on several factors among which
are fluid volume, fluid characteristics (viscosity, specific heat, thermal conductivity), heater power setting, operating temperature, and stirring. Thus the proportional band width may require adjustment for best bath stability when any of
these conditions change. Of these, the most significant factors affecting the optimum proportional width are heater power setting and fluid viscosity. The proportional band should be wider when the higher power setting is used so that
the change in output power per change in temperature remains the same. The
proportional band should also be wider when the fluid viscosity is higher because of the increased response time.
The proportional band width is easily adjusted from the bath front panel. The
width may be set to discrete values in degrees C or F depending on the selected
units. The optimum proportional band width setting may be determined by
monitoring the stability with a high resolution thermometer or with the control
ler percent output power display. Narrow the proportional band width to the
point at which the bath temperature begins to oscillate and then increase the
band width from this point to 3 or 4 times wider. Table 3 lists typical propor
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7312 TPW Maintenance Bath
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tional band settings for optimum performance with a variety of fluids at se
lected temperatures.
Table 3 Proportional Band - Fluid Table
Fluid Temperature Proportional Band Stability
Water 30°C 0.31°C ±0.003°C
Water 60°C 0.31°C ±0.003°C
Eth-Gly 50% 35°C 0.31°C ±0.005°C
Eth-Gly 50% 60°C 0.31°C ±0.005°C
Eth-Gly 50% 100°C 0.4°C ±0.010°C
Oil 200, 10cs 35°C 0.6°C ±0.004°C
Oil 200, 10cs 60°C 0.6°C ±0.004°C
Oil 200, 10cs 100°C 0.6°C ±0.004°C
Oil 710 200°C 0.4°C ±0.008°C
The proportional band adjustment may be accessed within the secondary menu.
Press the “SET” and “EXIT” buttons to enter the secondary menu and show the
heater power. Then press the “SET” button to access the proportional band.
-
S+E
Access heater power in secondary menu
12 Pct Heater power in percent
S
Access proportional band
Pb = 1.101C Proportional band setting
To change the proportional band, press the “UP” or “DOWN” buttons.
D
Decrement display
Pb=0.060C New proportional band setting
To accept the new setting and access the cutout set-point, press the “SET” but
ton. Pressing the “EXIT” button exits the secondary menu ignoring any
changes just made to the proportional band value.
S
Accept the new proportional band setting
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48
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9.8 Cutout
As a protection against software or hardware fault, shorted heater triac, or user
error, the bath is equipped with an adjustable heater cutout device that shuts off
power to the heater if the bath temperature exceeds a set value. This protects
the heater and bath materials from excessive temperatures and, most impor
tantly, protects the bath fluids from being heated beyond the safe operating
temperature preventing hazardous vaporization, breakdown, or ignition of the
liquid. The cutout temperature is programmable by the operator from the front
panel of the controller. It must always be set below the upper temperature limit
of the fluid and no more than 10 degrees above the upper temperature limit of
the bath.
If the cutout is activated because of excessive bath temperature, the power to
the heater is shut off and the bath cools. The bath cools until it reaches a few
degrees below the cutout set-point temperature. At this point, the action of the
cutout is determined by the setting of the cutout mode parameter.
The cutout has two selectable modes – automatic reset or manual reset. If the
mode is set to automatic, the cutout automatically resets when the bath temperature falls below the reset temperature allowing the bath to heat up again. If the
mode is set to manual, the heater remains disabled until the user manually resets the cutout.
9 Controller Operation
Cutout
-
The cutout set-point may be accessed within the secondary menu. Press the
“SET” and “EXIT” button to enter the secondary menu and show the heater
power. Then press the “SET” button twice to access the cutout set-point.
S+E
Access heater power in secondary menu
12 Pct Heater power in percent
S
Access proportional band
Pb = 0.101C Proportional band setting
S
Access cutout set-point
CO = 110C Cutout set-point
To change the cutout set-point, press the “UP” or “DOWN” button.
D
Decrement display
CO = 75C New cutout set-point
To accept the new cutout set-point, press the “SET” button.
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S
The next function is the configuration menu. Press the “EXIT” button to re
sume displaying the bath temperature.
Accept cutout set-point
9.9 Controller Configuration
The controller has a number of configuration and operating options and calibra
tion parameters, which are programmable via the front panel. These are ac
cessed from the secondary menu after the cutout set-point function by pressing
“SET”. There are five sets of configuration parameters—probe parameters, op
erating parameters, serial interface parameters, IEEE-488 interface parameters,
and controller calibration parameters. The menus are selected using the “UP”
and “DOWN” buttons and then pressing the “SET” button.
9.10 Probe Parameters
The probe parameter menu is indicated by,
PrObE Probe parameters menu
-
-
-
-
Press the “SET” button to enter the menu. The probe parameters menu contains
the parameters, D0 and DG, which characterize the resistance-temperature relationship of the thermistor control probe. These parameters may be adjusted to
improve the accuracy of the bath. This procedure is explained in detail in Section 11.
The probe parameters are accessed by pressing the “SET” button after the name
of the parameter is displayed. The value of the parameter may be changed using the “UP” and “DOWN” buttons. After the desired value is reached, press
the “SET” button to set the parameter to the new value. Pressing the “EXIT”
button causes the parameter to be skipped ignoring any changes that may have
been made.
9.10.1 D0
This probe parameter refers to the resistance of the control probe at 0°C. Nor
mally this is set for –25.2290 ohms.
9.10.2 DG
This probe parameter refers to the average sensitivity of the probe between 0
and 100°C. Normally this is set for 186.7940.
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50
9.11 Operating Parameters
The operating parameters menu is indicated by,
Page 53
Par Operating parameters menu
9 Controller Operation
Operating Parameters
Press the “UP” button to enter the menu. The operating parameters menu con
tains the cutout reset mode parameter.
9.11.1 Cutout Reset Mode
The cutout reset mode determines whether the cutout resets automatically when
the bath temperature drops to a safe value or must be manually reset by the
operator.
The parameter is indicated by,
CtorSt Cutout reset mode parameter
Press the “SET” button to access the parameter setting. Normally the cutout is
set for manual mode.
Cto=rst Cutout set for manual reset
To change to automatic reset mode, press the “UP” button and then the “SET”
button.
Cto=Auto Cutout set for automatic reset
-
9.11.2 Triple Point of Water Cutout
The triple point of water cutout protects the TPW cell in case of system failure,
which may cause the bath to rapidly cool below the maintenance set-point. This
could cause the cell to rupture due to the expansion of ice. The cutout uses a
thermistor probe sensor and disengages the refrigeration compressor. If the
probe is replaced, the cutout board must be recalibrated. (See Section 12). The
user may set the cutout temperature. A typical set-point is from –0.3 to –0.5°C.
If undesired trips occur, the temperature may be reduced. The adjustment range
is ±1.27°C from 0°Cin0.01°C increments.
The triple point of water cutout engages for three reasons: 1) the controller
does not send a watch dog signal to the cutout board (controller lockup), 2) the
thermistor sensor is disconnected or opens, or 3) the bath goes below the cutout
set-point. (This could be if the temperature controller set-point is too low or if
the heater fails.) When the TPW cutout is triggered, the display alternately
flashes tP-cto and the current bath temperature. The serial port outputs “TPW
Cutout” every three seconds. Pressing any button causes the cutout error mes
sage to stop being output until another TPW cutout error has occurred. Each
time the cutout is tripped, the bath temperature set-point automatically in
creases in 0.5°C increments until the set-point has reached a maximum of
25°C.
-
-
The parameter is indicated by,
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7312 TPW Maintenance Bath
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tP CO Triple point of water cutout parameter
Press the “SET” button to access the activation selection. Press the “UP” or
“DOWN” button to turn the cutout on or off and then press the “SET” button.
Normally the cutout is ON.
Press the “EXIT” button to return to the operating parameters menu.
tP SP Triple point of water set-point selection parameter
Press the “SET” button to access the parameter setting.
C -0.30 Cutout temperature in degrees C or F
To change the cutout temperature, use the “UP” or “DOWN” button. To accept
the new cutout set-point, press the “SET” button.
Press the “EXIT” button to return to the operating parameters menu.
9.12 Serial Interface Parameters
The serial RS-232 interface parameters menu is indicated by,
SErIAL Serial RS-232 interface parameters menu
The serial interface parameters menu contains parameters, which determine the
operation of the serial interface. The parameters in the menu are – BAUD rate,
sample period, duplex mode, and linefeed.
9.12.1 BAUD Rate
The BAUD rate is the first parameter in the menu. The BAUD rate setting determines the serial communications transmission rate.
The BAUD rate parameter is indicated by,
BAUd Serial BAUD rate parameter
Press the “SET” button to choose to set the BAUD rate. The current BAUD rate
value is displayed.
1200 b Current BAUD rate
52
The BAUD rate of the bath serial communications may be programmed to 300,
600, 1200, or 2400 BAUD. Use the “UP” or “DOWN” button to change the
BAUD rate value.
2400 b New BAUD rate
Page 55
Press the “SET” button to set the BAUD rate to the new value or the “EXIT”
button to abort the operation and skip to the next parameter in the menu.
9.12.2 Sample Period
The sample period is the next parameter in the serial interface parameter menu.
The sample period is the time period in seconds between temperature measure
ments transmitted from the serial interface. If the sample rate is set to 5, the
bath transmits the current measurement over the serial interface approximately
every five seconds. The automatic sampling is disabled with a sample period of
0. The sample period is indicated by,
SAMPLE Serial sample period parameter
Press the “SET” button to choose to set the sample period. The current sample
period value is displayed.
SA = 1 Current sample period (seconds)
9 Controller Operation
Serial Interface Parameters
-
Adjust the value with the “UP” or “DOWN” button and then use the “SET”
button to set the sample rate to the displayed value.
SA = 60 New sample period
9.12.3 Duplex Mode
The next parameter is the duplex mode. The duplex mode may be set to full duplex or half duplex. With full duplex any commands received by the bath via
the serial interface are immediately echoed or transmitted back to the device of
origin. With half duplex the commands are executed but not echoed. The du
plex mode parameter is indicated by,
DUPL Serial duplex mode parameter
Press the “SET” button to access the mode setting
DUP=FULL Current duplex mode setting
The mode may be changed using the “UP” or “DOWN” button and then press
ing the “SET” button.
-
-
DUP=HALF New duplex mode setting
9.12.4 Linefeed
The final parameter in the serial interface menu is the linefeed mode. This pa
rameter enables (on) or disables (off) transmission of a linefeed character (LF,
-
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ASCII 10) after transmission of any carriage-return. The linefeed parameter is
indicated by,
LF Serial linefeed parameter
Press the “SET” button to access the linefeed parameter.
LF=On Current linefeed setting
The mode may be changed using the “UP” or “DOWN” button and then press
ing the “SET” button.
LF=OFF New linefeed setting
9.13 IEEE-488 Parameters
Baths may optionally be fitted with an IEEE-488 GPIB interface. In this case
the user may set the interface address and the transmission termination character within the IEEE-488 parameter menu. This menu does not appear on baths
not fitted with the interface. The menu is indicated by,
IEEE IEEE-488 parameters menu
Press the “SET” button to enter the menu.
9.13.1 IEEE-488 Address
IEEE-488 interface must be configured to use the same address as the external
communicating device. The address is indicated by,
-
54
AddrESS IEEE-488 interface address
Press the “SET” button to access the address setting.
Add=22 Current IEEE-488 interface address
Adjust the value with the “UP” or “DOWN” button and then use the “SET”
button to set the address to the displayed value.
Add=15 New IEEE-488 interface address
9.13.2 Transmission Termination
The transmission termination character can be set to carriage return only, line
feed only, or carriage return and linefeed. Regardless of the option selected, the
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9 Controller Operation
Calibration Parameters
instrument interprets either a carriage return or a linefeed as a command termi
nation during reception.
The termination parameter is indicated with,
EOS IEEE-488 termination
Press the “SET” button to access the termination setting.
EOS=Cr Present IEEE-488 termination
Use the “UP” or “DOWN” button to change the selection.
EOS=LF New termination selection
Use the “SET” button to save the new selection.
9.14 Calibration Parameters
The operator of the bath controller has access to a number of the bath calibration constants namely CTO, H, and L. These values are set at the factory and
must not be altered. The correct values are important to the accuracy and
proper and safe operation of the bath. These parameters should not be adjusted
except in the event the controller’s memory fails. The user may then restore
these values to the factory settings. A list of these constants and their settings
are supplied to the user on the Report of Test with the manual.
-
CAUTION: DO NOT change the values of the bath calibration constants
from the factory set values. The correct setting of these parameters is im
portant to the safety and proper operation of the bath.
The calibration parameters menu is indicated by,
CAL Calibration parameters menu
Press the “SET” button five times to enter the menu.
9.14.1 CTO
Parameter CTO sets the calibration of the over-temperature cutout. This param
eter is not adjustable by software but is adjusted with an internal potentiometer.
For the 7312 bath this parameter should read 160.
9.14.2 H and L
These parameters set the upper and lower set-point limits of the bath. DO NOT
change the values of these parameters from the factory set values. To do so may
-
-
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present danger of the bath exceeding its temperature range causing damage or
fire.
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10 Digital Communication Interface
10 Digital Communication Interface
The 7312 bath is capable of communicating with and being controlled by other
equipment through the digital interface. Two types of digital interface are avail
able—the RS-232 serial interface, which is standard, and the IEEE-488 GPIB
interface which is optional.
With a digital interface the bath may be connected to a computer or other
equipment. This allows the user to set the bath temperature, monitor the tem
perature, and access any of the other controller functions, all using remote com
munications equipment. In addition the cooling may be controlled using the
interface. To control the cooling with the interface the cooling power switch
must be OFF.
10.1 Serial Communications
The RS-232 serial interface allows serial digital communications over fairly
long distances (15.24 meters). With the serial interface the user may access any
of the functions, parameters and settings discussed in Section 10, Controller
Operation with the exception of the BAUD rate setting. The serial interface operates with eight data bits, one stop bit, and no parity.
Serial Communications
-
-
-
10.1.1 Wiring
The serial communications cable attaches to the bath through the DB-9 connector at the back of the instrument. Figure 9 shows the pin-out of this connector
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7312 TPW Maintenance Bath
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and suggested cable wiring. To eliminate noise, the serial cable should be
shielded with low resistance between the connector (DB-9) and the shield.
Figure 9 Serial Communications Cable Wiring
10.1.2 Setup
Before operation, the serial interface of the bath must first be set up by pro
gramming the BAUD rate and other configuration parameters. These parame
ters are programmed within the serial interface menu.
To enter the serial parameter programming mode first, press the “EXIT” button
while pressing the “SET” button and release to enter the secondary menu. Press
the “SET” button repeatedly until the display reads “ProbE”. This is the menu
selection. Press the “UP” button repeatedly until the serial interface menu is in
dicated with “SErIAL”. Finally press the “SET” button to enter the serial pa
rameter menu. The serial interface parameter menu contains the BAUD rate, the
sample rate, the duplex mode, and the linefeed parameter.
10.1.2.1 BAUD Rate
The BAUD rate is the first parameter in the menu. The display prompts with
the BAUD rate parameter by showing “BAUd”. Press the “SET” button to
choose to set the BAUD rate. The current BAUD rate value is displayed. The
-
-
-
-
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BAUD rate of the bath may be programmed to 300, 600, 1200, or 2400 BAUD.
The BAUD rate is pre-programmed to 2400 BAUD. Use “UP” or “DOWN” to
change the BAUD rate value. Press the “SET” button to set the BAUD to the
new value or the “EXIT” button to abort the operation and skip to the next pa
rameter in the menu.
10.1.2.2 Sample Period
The sample period is the next parameter in the menu and prompted with
“SAMPLE”. The sample period is the time period, in seconds, between temper
ature measurements transmitted from the serial interface. If the sample rate is
set to 5, the bath transmits the current measurement over the serial interface ap
proximately every five seconds. The automatic sampling is disabled with a
sample period of 0. Press the “SET” button to choose to set the sample period.
Adjust the period with the “UP” or “DOWN” button and then use the “SET” to
set the sample rate to the displayed value.
10.1.2.3 Duplex Mode
10 Digital Communication Interface
IEEE-488 Communication (optional)
-
-
-
The next parameter is the duplex mode indicated with “dUPL”. The duplex
mode may be set to half duplex (“HALF”) or full duplex (“FULL”). With full
duplex any commands received by the bath via the serial interface are immediately echoed or transmitted back to the device of origin. With half duplex the
commands are executed but not echoed. The default setting is full duplex. The
mode may be changed using “UP” or “DOWN” and pressing “SET”.
10.1.2.4 Linefeed
The final parameter in the serial interface menu is the linefeed mode. This parameter enables (“On”) or disables (“OFF”) transmission of a linefeed character (LF, ASCII 10) after transmission of any carriage-return. The default setting
is with linefeed on. The mode may be changed using “UP” or “DOWN” and
pressing “SET”.
10.1.3 Serial Operation
Once the cable has been attached and the interface set up properly the control
ler immediately begins transmitting temperature readings at the programmed
rate. The set-point and other commands may be sent to the bath via the serial
interface to set the bath and view or program the various parameters. The inter
face commands are discussed in Section 11.3, Interface Commands.
-
-
10.2 IEEE-488 Communication (optional)
The IEEE-488 interface is available as an option. Baths supplied with this op
tion may be connected to a GPIB type communication bus, which allows many
instruments to be connected and controlled simultaneously. To eliminate noise,
the GPIB cable should be shielded.
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10.2.1 Setup
To use the IEEE-488 interface connect an IEEE-488 standard cable to the back
of the bath, set the device address, and set the transmission termination
character.
To enter the IEEE-488 parameter programming menu, press the “EXIT” and
the “SET” button simultaneously and then release to enter the secondary menu.
Press the “SET” button repeatedly until the display reaches “PrObE”. Press the
“UP” button repeatedly until the IEEE-488 interface menu is indicated with
“IEEE”. Press the “SET” button to enter the IEEE-488 parameter menu.
10.2.1.1 IEEE-488 Address
The IEEE-488 address is prompted with “AddrESS”. Press the “SET” button to
program the address. The default address is 22. If necessary, change the device
address of the bath to match the address used by the communication equip
ment. To change the device address, press the “UP” or DOWN” button and then
the “SET” button.
-
10.2.1.2 Transmission Termination
The IEEE-488 transmission termination is prompted with “EOS”. Press the
“SET” button to access the termination character. The present setting is displayed. Press the “UP” or “DOWN” button to change the setting. Press the
“SET” button to save the new selection.
10.2.2 IEEE-488 Operation
Commands may now be sent via IEEE-488 interface to read or set the temperature or access other controller functions. All commands are ASCII character
strings and are terminated with a carriage-return (CR, ASCII 13). Interface
commands are listed below.
10.3 Interface Commands
The various commands for accessing the bath controller functions via the digi
tal interfaces are listed in this section (see Table 4). These commands are used
with both the RS-232 serial interface and the IEEE-488 GPIB interface. In ei
ther case the commands are terminated with a carriage-return character. The in
terface makes no distinction between upper and lower case letters, hence either
may be used. Commands may be abbreviated to the minimum number of let
ters, which determines a unique command. A command may be used to either
set a parameter or display a parameter depending on whether or not a value is
sent with the command following a “=” character. For example, an “s”<cr> re
turns the current set-point and an “s=50.00”<cr> sets the set-point to 50.00
degrees.
-
-
-
-
-
60
In the following list of commands, characters or date within brackets, “[“ and
“]”, are optional. A slash, “/”, denotes alternate characters or data. Numeric
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Table 4 Interface Command Summary.
10 Digital Communication Interface
Interface Commands
Command
Command Description
Display Temperature
Read current set-point s[etpoint] s set: 9999.99 {C or F} set: 100.000 C
Set current set-point to n s[etpoint]=n s=100 Instrument
Read vernier v[ernier] v v: 9.99999 v: 0.00000
Set vernier to n v[ernier]=n v=.00001 Depends on
Read temperature t[emperature] t t: 9999.99 {C or F} t: 55.69 C
Read temperature units u[nits] u u: x u: c
Set temperature units: u[nits]=c/f
Set temperature units to Celsius u[nits]=c u=c
Set temperature units to
Fahrenheit
Secondary Menu
Read proportional band setting pr[op-band] pr pr: 999.9 pr: 15.9
Set proportional band to
Read cut-out setting c[utout] c c: 9999 {x},{xxx} c: 110 C, in
n
Format
u[nits]=f u=f
pr[op-band]=n pr=8.83 Depends on
Command
Example Returned
Returned
Example
Acceptable
Values
Range
Configuration
CorF
Configuration
Set cut-out setting: c[utout]=n/r[eset]
Set cut-out to
Reset cut-out now c[utout]=r[eset] c=r
Read heater power
(duty cycle)
Configuration Menu
Probe Menu
Read D0 calibration parameter *d0 *d0 d0: 999.9999 d0: -25.2290
Set D0 calibration parameter to
Read DG calibration parameter *dg *dg dg: 999.9999 dg:186.9740
Set DG calibration parameter to
Operating Parameters Menu
Read cut-out mode cm[ode] cm cm: {xxxx} cm: AUTO
Set cut-out mode: cm[ode]=r[eset]/a[uto]
Set cut-out to be reset manually cm[ode]=r[eset] cm=r
n
degrees c[utout]=n c=110 Temperature
po[wer] po po: 9999 po: 1
n
*d0=n *d0=-25.2290 -999.9999 to
n
*dg=n *dg=186.9740 -999.9999 to
Range
999.9999
999.9999
RESET or
AUTO
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Interface Command Summary continued
Command
Command Description
Set cut-out to be reset
automatically
Read water triple point tpco tpco tpco:{ON or OFF} tpco=ON
Set water triple point tpco=ON/OFF tpco=ON ON or OFF
Read water triple point cutout
set-point
Set water triple point cutout
set-point
Serial Interface Menu
Read serial sample setting sa[mple] sa sa: 9 sa: 1
Set serial sampling setting to
seconds
Set serial duplex mode: du[plex]=f[ull]/h[alf]
Set serial duplex mode to full du[plex]=f[ull] du=f
Set serial duplex mode to half du[plex]=h[alf] du=h
Set serial linefeed mode: lf[eed]=on/of[f]
Set serial linefeed mode to on lf[eed]=on lf=on
Set serial linefeed mode to off lf[eed]=of[f] lf=of
Format
cm[ode]=a[uto] cm=a
tpsp=
n
tpsp=
n
n
sa[mple]=n sa=0 0 to 4000
Command
Example Returned
tpsp tpsp=99.99C tpsp=–0.31C
tpsp=–0.33 ±1.27°C
Returned
Example
Acceptable
Values
(±2.28°F)
FULL or HALF
ON or OFF
Calibration Menu
Read low set-point limit value *tl[ow] *tl tl: 999 tl: –80
Set low set-point limit to
Read high set-point limit value *th[igh] *th th: 999 th: 205
Set high set-point limit to
Miscellaneous (not on menus)
Read firmware version number *ver[sion] *ver ver.9999,9.99 ver.2100,3.56
Read structure of all commands h[elp] h list of commands
Read Refrigeration f2 f2 f2:9 f2:0
Set Refrigeration f2=1/0 0or1
Set Refrigeration to on f2=
Set Refrigeration to off f2=
Legend: [] Optional Command data
Note: When DUPLEX is set to FULL and a command is sent to READ, the command is returned followed by a
n
n
*tl[ow]=n *tl=-80 –5 to 25°C
*th[igh]=n *th=205 25 to 110°C
n
n
{} Returns either information
n Numeric data supplied by user
9 Numeric data returned to user
x Character data returned to user
carriage return and linefeed. Then the value is returned as indicated in the RETURNED column.
f2=1
f2=0
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10 Digital Communication Interface
Power Control Functions
data, denoted by “n”, may be entered in decimal or exponential notation. Char
acters are shown in lower case although upper case may be used. Spaces may
be added within command strings and are simply ignored. Backspace (BS,
ASCII 8) may be used to erase the previous character. A terminating CR is im
plied with all commands.
10.4 Power Control Functions
The digital interface is capable of controlling the cooling function so that the
instrument can be remotely operate at any temperature within the range of the
bath. To allow the interface to control the cooling, disable the front panel con
trols by switching the refrigeration switch to OFF. Otherwise, the interface
would not be able to switch these functions off.
To control the refrigeration power with the digital interface, the front panel re
frigeration switch must be off. The refrigeration power function is controlled
with the “F2” command. Setting the “F2” value to 0 turns the refrigeration off
and setting the “F2” value to 1 turns the refrigeration on. “F2” alone returns 0
or 1 showing the state of the refrigeration power control as shown in the following table.
Function Command 0 1
Refrigeration F2 off on
-
-
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11 Calibration Procedure
11 Calibration Procedure
Calibration Points—2 Point Calibration
In some instances the user may want to calibrate the bath to improve the tem
perature set-point accuracy. Calibration is done by adjusting the controller
probe calibration constants DO and DG so that the temperature of the bath as
measured with a standard thermometer agrees more closely with the bath
set-point. The thermometer used must be able to measure the bath fluid temper
ature with higher accuracy than the desired accuracy of the bath. By using a
good thermometer and by carefully following the procedure, the bath can be
calibrated to an accuracy of better than 0.1°C over a range of 50 degrees.
11.1 Calibration Points—2 Point Calibration
In calibrating the bath DO and DG are adjusted to minimize the set-point error
at each of two different bath temperatures. Any two reasonably separated bath
temperatures may be used for the calibration however best results are obtained
when using bath temperatures which are just within the most useful operating
range of the bath. The farther apart the calibration temperatures, the larger the
calibrated temperature range but the calibration error is also greater over the
range. For instance, if 20°C and 80°C are chosen as the calibration temperatures, the bath may achieve an accuracy of say ±0.2°C over the range 20 to
80°C. Choosing 30°C and 70°C may allow the bath to have a better accuracy of
maybe ±0.05°C over the range 30 to 70°C but outside the range the accuracy
may be only ±0.5°C.
-
-
11.2 Measuring the Set-point Error
The first step in the calibration procedure is to measure the temperature errors
(including sign) at the two calibration temperatures. First, set the bath to the
lower set-point, t
. Wait for the bath to reach the set-point and allow 15 minutes
L
to stabilize at that temperature. Check the bath stability with the thermometer.
When both the bath and the thermometer have stabilized, measure the bath tem
perature with the thermometer and compute the temperature error, err
is the actual bath temperature minus the set-point temperature. For example, if
the bath is set for a lower set-point of, t
=20°C and the bath reaches a measured
L
temperature of 19.7°C then the error is –0.3°C.
Next, set the bath for the upper set-point, t
bath temperature and compute the error, err
, and after stabilizing measure the
H
. For example, suppose the bath
H
was set for 80°C and the thermometer measured 80.1°C giving an error of
+0.1°C.
11.3 Computing DO and DG
Before computing the new values for DO and DG the current values must be
known. The values may be found by either accessing the probe calibration
menu from the controller panel or by inquiring through the digital interface.
,which
L
-
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The user should keep a record of these values in case they may need to be re
stored in the future. The new values DO’ and DG’ are computed by entering the
old values for DO and DG, the calibration temperature set-points, t
the temperature errors, err
D
DG
err t D err t D
()()
0
LH HL
⎡
err err
′=
HL
⎢
tt
HL
⎣
00
−− −
tt
−
HL
−
1
+
−
and errH, into the following equations,
L
0′=
D
+
⎤
DG
⎥
⎦
and tH,and
L
For example, if DO and DG were previously set for –25.229 and 186.9740 respectively and the data for t
,errL,anderrHwere as given above then the
L,tH
new values D0′ and DG′ would be computed as –25.831 and 188.220 respectively. Program the new values D0 and DG into the controller. The new constants are used the next time the bath temperature is set. Check the calibration
by setting the temperature to t
and tHand measuring the errors again. If de-
L
sired, the calibration procedure may be repeated again to further improve the
accuracy.
11.4 Calibration Example
The bath is to be used between 25 and 75°C and it is desired to calibrate the
bath as accurately as possible for operation within this range. The current values for D0 and DG are –25.229 and 186.974 respectively. The calibration
points are chosen to be 25.00 and 75.00°C. The measured bath temperatures are
24.869 and 74.901°C respectively. Refer to Figure 10 for applying the equations to the example data and computing the new probe constants.
11.5 Single Point Calibration
When calibrating the bath for applications emphasizing a single temperature, a
single point calibration can be quicker, easier and more accurate. These appli
cations include maintenance of a triple point of water cell near zero degrees
Celsius or for the gallium point near 30°C. An adjustment of only the D0 cali
bration constant is made in this process. The advantage of calibration is to have
the bath set-point temperature more closely reflect the desired bath tempera
ture. While this procedure improves the accuracy at a specific set-point, the re
sults may not be accurate enough alone to make the baths final temperature
adjustment. For example, for the maintenance of a triple point of water cell, the
bath temperature must be known to within one thousandth of a degree Celsius.
The calibration of the bath is not intended to get that close. Final adjustments
-
-
-
-
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D0 = -25.229
DG = 0.0028530
t
= 25.00°C
L
measured t = 24.869°C
t
= 75.00°C
H
measured t = 74.901°C
Compute errors,
err
= 24.869 – 25.00°C = –0.131°C
L
err
= 74.901 – 75.00°C = –0.099°C
H
11 Calibration Procedure
Measuring the Set-point Error
Compute D0,
0131 75 0 25 229 0 099 25 0 25 22
D0
−−−−− −−(.)(.( .))(.)(.( .
′=
75 0 25 0
..
Compute DG,
⎡
−−−
(.)(.)
DG′=
Figure 10 Sample Calibration Computations
0 099 0131
⎢
⎣
..
75 0 25 0
−
⎤
+
1 0 0028530 0 0028548
⎥
⎦
must be made using a thermometer and readout capable of making measure
ments to one thousandth of a degree.
11.6 Measuring the Set-point Error
The first step in this procedure is to measure the set-point error (including the
sign) at the desired temperature. Set the bath to the desired set-point, for exam
ple 0.008°C for the triple point of water cell maintenance. Verify that the ver
nier is set at 0. Wait for the bath to reach that temperature and allow 30 minutes
for the bath to stabilize at that temperature. Check the bath stability with the
thermometer. When both the bath and the thermometer have stabilized, measure
the bath temperature with the thermometer and compute the temperature error,
which is the set-point temperature minus the actual bath temperature.
−
..
=
9
))
25 229 25392
(.) .
+− =−
-
-
-
Error = T
sp–Tactual
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7312 TPW Maintenance Bath
User’s Guide
Example:
Actual temperature = +0.132°C
Set point temperature = +0.008°C
error = +0.008– (+0.132) = -0.124 (including sign)
11.7 Computing D0
Before computing the new values for D0, the current value must be known. The
value may be found by either accessing the probe calibration menu from the
controller panel or by inquiring through the digital interface. The user should
keep a record of this value in case it may need to be restored in the future. The
new value D0’ is computed by subtracting the temperature error from the old
value for D0 as follows.
D0′ =D0–error
Example:
Old D0 = -25.438
error = -0.124°C
D0′ = –25.438 – (–0.224) = –25.662
Enter the new D0 value into the controller and press the “SET” button. Wait for
the temperature to stabilize and measure the temperature again. If desired, the
calibration procedure may be repeated to further improve the accuracy.
11.8 Calibrating the Triple Point of Water Cutout
The under temperature cutout is provided to protect the triple point of water
cell in case there is a temperature controller or sensor failure that would cause
the bath to cool rapidly below the set-point temperature. Such a failure could
cause the cell to rupture due to rapid expansion of the ice inside it. The cutout
deactivates the refrigeration thereby preventing the problem.
CAUTION: Only trained personnel should operate calibration equipment.
The cutout is calibrated at the triple point temperature at the factory. It may
need to be recalibrated from time to time if there is drift in the cutout tempera
ture or if the cutout probe has been replaced. The actual cutout temperature
may be observed by setting the bath to a temperature well below the cutout
set-point and monitoring the bath temperature until the cutout activates. When
the display flashes tP-c-out, note the temperature. If the error is less than
0.5°C, it may be compensated for by resetting the water triple point cutout. For
greater errors it may be best to recalibrate the cutout.
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11 Calibration Procedure
Calibrating the Triple Point of Water Cutout
The cutout is calibrated by adjusting a potentiometer inside the unit while the
bath is at the triple point maintenance temperature. The bath temperature
should be known to within ±0.05°C. A DVM capable of measuring accurately
to 10mV is required.
To access the cutout circuit board, the front panel must be removed. Be sure to
disconnect the power to the unit before beginning. It is best to move quickly to
avoid much bath temperature change. Begin by removing the 4 screws attach
ing the sloping controller panel. Lift up the controller panel to access the fas
-
teners attaching the front sheet metal panel. Remove the two fasteners located
at the top left and right corners of the panel. The bottom of the panel is retained
by a screw on either side of the panel that is in a key-hole shaped slot. Lift up
the panel and wiggle slightly so that the screw heads come out through the
larger portion of the slot. The bottom screws are not to be removed. Once the
panel is removed, set it aside and temporarily replace the controller panel rein
-
stalling the screws to hold it in place.
Reestablish the power connection to the bath and allow the bath to regain stable
control at the required set-point. This procedure takes 15 minutes or longer de
pending on how long the bath has been off and how far it has drifted off temperature. Be aware that the bath has a low voltage line monitor that activates
when the power is disconnected. Several minutes are required before the unit is
permitted to turn on. Note the amber light on the back of the unit.
-
WARNING: Shock hazard! High Voltage power is accessible.
Identify the cutout PC board on the left side of a sheet metal shelf below the
temperature controller boards. Locate on the cutout board the two test points
TP1 and TP2 and attach the DVM.
In order to prevent the cutout from activating during adjustment it must be
turned off in the controller menu. To disable the low temperature cutout, access
the operating parameters menu. Follow the instructions in Section 9.11.2 and
set the triple point cutout (tP CO) to OFF toggling with either the up or down
keys. Set the water triple point cutout to 0.01°C. With the bath controlling at
0°C to 0.01°C, adjust VR1 on the board until the voltage reads 0 volts. After
the adjustment, return the cutout to the ON condition and set the water triple
point cutout set-point to –0.3°C.
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12 Charging Instructions
12 Charging Instructions
Leak Testing
The 7312 uses R-134a with a polyolester oil. Care must be taken to avoid con
tamination from other types of refrigerants and oils.
12.1 Leak Testing
Leak testing should be done with equipment designed for use with R-134a.
Bubble, electronic halogen detector, or ultra-sonic leak testing may be viable in
some instances.
12.2 Evacuation
DO NOT leave the system open for more than 15 minutes. Polyolester oils are
very hygroscopic. Evacuate the system to a minimum of 200 microns. Evacuate
from both high and low sides of the system. Schrader valves provide access to
the system.
12.3 Charging
After evacuation, charge the system with 160 grams of R-134a. Set the suction
pressure to 8-10 psig for operation.
-
NOTE: A fan must be placed in front of the condenser if the unit is operated with the side panels removed. The unit requires the side panels to be
installed for proper airflow across the condenser.
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13 Maintenance
A battery is used to maintain operating parameters in the unit. All operat
•
ing parameters, including calibration parameters should be checked on a
regular basis to insure accuracy and proper operation of the instrument.
See the troubleshooting section for the procedure on checking the status
of the battery.
The calibration instrument has been designed with the utmost care. Ease
•
of operation and simplicity of maintenance have been a central theme in
the product development. Therefore, with proper care the instrument
should require very little maintenance. Avoid operating the instrument in
dirty or dusty environments.
If the outside of the bath becomes soiled, it may be wiped clean with a
•
damp cloth and mild detergent. Do not use harsh chemicals on the surface, which may damage the paint.
Periodically check the fluid level in the bath to ensure that the level has
•
not dropped. A drop in the fluid level affects the stability of the bath.
Changes in fluid level are dependent upon several factors specific to the
conditions in which the equipment is used. A schedule cannot be outlined
to meet each set of conditions. Therefore, the bath should be checked
weekly and adjustments made as required.
13 Maintenance
-
• Heat transfer medium lifetime is dependent upon the type of medium and
the conditions of use. The fluid should be checked at least every month
for the first year and regularly thereafter. This fluid check provides a
baseline for knowledge of bath operation with clean, usable fluid. Once
some fluids have become compromised, the break down can occur rapidly. Particular attention should be paid to the viscosity of the fluid. A significant change in the viscosity can indicate that the fluid is contaminated,
being used outside of its temperature limits, contains ice particles, or is
close to a chemical breakdown. Once data has been gathered, a specific
maintenance schedule can be outlined for the instrument. Refer to Section
9, General Operation, for more information about the different types of
fluids used in calibration baths.
•
Depending on the cleanliness of the environment, the internal parts (parts
behind the front cover only) of the cold bath should be cleaned and/or
checked at least every month for dust and dirt. Particular attention should
be paid to the condensing coil fins. The fins should be vacuumed or
brushed free of dust and dirt on a regular basis. Dust and dirt inhibit the
operation of the condensing coil and thus compromise the performance
and lifetime of the cooling system.
•
If a hazardous material is split on or inside the equipment, the user is re
sponsible for taking the appropriate decontamination steps as outlined by
the national safety council with respect to the material. MSDS sheets ap
plicable to all fluids used in the baths should be kept in close proximity to
the instrument.
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7312 TPW Maintenance Bath
User’s Guide
If the mains supply cord becomes damaged, replace it with a cord with
•
the appropriate gauge wire for the current of the bath. If there are any
questions, call an Authorized Service Center for more information.
Before using any cleaning or decontamination method except those rec
•
ommended by Hart, users should check with an Authorized Service Cen
ter to be sure that the proposed method does not damage the equipment.
If the instrument is used in a manner not in accordance with the equip
•
ment design, the operation of the bath may be impaired or safety hazards
may arise.
The over-temperature cutout should be checked every 6 months to see that
•
it is working properly. In order to check the user selected cutout, follow
the controller directions (Section 10.2) for setting the cutout. Both the
manual and the auto reset option of the cutout should be checked. Set the
bath temperature higher than the cutout. Check to see if the display
flashes cutout and if the temperature is decreasing. Note: When checking
the over-temperature cutout, be sure that the temperature limits of the bath
fluid are not exceeded. Exceeding the temperature limits of the bath fluid
could cause harm to the operator, lab, and instrument.
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14 Troubleshooting
This section contains information on troubleshooting, CE Comments, and a
wiring diagram. This information pertains to a number of bath models and cer
tain specifics may not pertain to your model.
14.1 Troubleshooting
In the event that the instrument appears to function abnormally, this section
may help to find and solve the problem. Several possible problem conditions
are described along with likely causes and solutions. If a problem arises, please
read this section carefully and attempt to understand and solve the problem. If
the probe seems faulty of the problem cannot otherwise be solved, contact an
Authorized Service Center (see Section 1.3) for assistance. Be sure to have the
model number, serial number, and voltage of your instrument available.
Problem Causes and Solutions
The bath does not turn
on and the display remains blank
If a fault condition exists upon application of power, the bath will not energize.
The bath needs to be plugged in to the line voltage for at least 2 minutes before
turning power on. This is only necessary for the first time that the bath is energized or when it is moved from one location to another.
14 Troubleshooting
Troubleshooting
-
If a high or low voltage condition exists for longer than 5 seconds, the compressor is de-energized and the “Mains Out of Range” light on the back panel illuminates indicating a fault condition.
Re-energization is automatic upon correction of the fault condition and after a
delay cycle of about 2 minutes.
High and low voltage protection limits at 115 VAC:
Voltage Cutout: ±12.5% (101 – 129 VAC)
Voltage Cutin: ±7.5% (106 – 124 VAC)
High and low voltage protection limits at 230 VAC:
Voltage Cutout: ±12.5% (203 – 257 VAC)
Voltage Cutin: ±7.5% (213 – 247 VAC)
See the Caution in the front of this manual for additional information.
Testing the Line Voltage – If the power line voltage is too low (90% of the
compressor’s rated voltage), the compressor could be damaged. Place a DVM
in the supply line on the wall that feeds the bath. Measure the line voltage under
load (with the bath on). If the line voltage is low or marginal, disconnect any
other devices that are using the same line. Alternately, move the bath to a loca
tion where the supply voltage is good. If none of these are possible, contact an
electrician to re-route the correct power. If necessary, you can inspect the oper
ation of the line monitor by opening the electronics cover. See the Caution at
the front of this manual for a summary of the ICM491 operation. Hart does not
recommend adjustment of the operating voltage in order to use the instrument.
Instead, an electrician should be consulted to alleviate the problem with the
power source.
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7312 TPW Maintenance Bath
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Problem Causes and Solutions
The heater indicator LED
stays red but the temper
ature does not increase
The controller display
flashes “CUTOUT” and
the heater does not
operate
If the display does not show “cutout” and shows the correct bath temperature,
consider the following possibilities:
-
No heating. This is caused by blown heater fuses and/or burned out heaters.
Check the heater fuses to make sure that they are still good. Access the heater
fuses by removing the front panel under the display electronics. If they are
blown, and continue to blow when replaced, the heaters may be shorted. If you
suspect that the heaters are shorted or burned out, contact an Authorized Ser
vice for assistance.
If the display flashes “cut-out” alternately with the correct process temperature,
check the following:
Wrong cutout setting. The cutout disconnects power to the heaters when the
bath temperature exceeds the cutout set-point. This causes the bath tempera
ture to drop back down to a safe value. If the cutout mode is set to “AUTO”, the
heater switches back on when the temperature drops. If the mode is set to “RE
SET”, the heater only comes on again when the temperature is reduced and
when the cutout is manually reset by the operator. (Refer to Section 10.8.)
-
-
-
The display flashes
“CUTOUT” alternately
with an incorrect process
temperature
The controller displays
the wrong temperature
and the bath continually
heats or cools regardless
of the set-point value
Check that the cutout set-point is adjusted to 10 or 20°C above the desired
maximum bath operating temperature and that the cutout mode is set as
desired.
Continuous cutout. If the cutout activates when the bath temperature is well
below the cutout set-point or the cutout does not reset when the bath temperature drops and it is manually reset, the cutout circuitry may be faulty. Try performing the Factory Reset Sequence explained below.
Factory Reset Sequence - Hold the “SET” and “EXIT” keys down at the same
time while powering up the unit. The display shows “-init”, the model number,
and the firmware version. Each of the controller parameters and calibration constants must be re-programmed. The values can be found on the Report of Test
that was shipped with the instrument.
Low battery. A problem could exist with the memory back-up battery. If the bat
tery voltage is insufficient to maintain the memory, data may become scrambled
causing problems. A nearby large static discharge may also affect data in mem
ory. Access the battery by removing the L-shaped panel covering the display
electronics.
Corrupt controller memory. If the problem reoccurs after the battery is re
placed, initialize the memory by performing a Factory Reset Sequence (de
scribed in a previous solution).
Defective control probe. The bath control probe may be disconnected, burned
out, or shorted. Check first that the probe is connected properly to the connec
tor, J2, of the analog board.
The probe may be checked with an ohmmeter to see if it is open or shorted.
The probe is a platinum 4-wire Din 43760 type. The probe connector resistance
should read 9.4K ohms between pins 1 and 3, 3.2 K ohms between pins 3 and
4, 12.4K ohms between pins 1 and 4, and no current on pin 2.
-
-
-
-
-
76
Corrupt controller memory. Initialize the memory by performing a Factory Re
set Sequence (described in a previous solution).
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Problem Causes and Solutions
The controller controls or
attempts to control at an
inaccurate temperature
The controller shows that
it is controlling at the
proper temperature, but
the bath temperature is
unstable
If the controller appears to operate normally except that the bath’s temperature
does not agree with the temperature measured by the user’s reference ther
mometer to within the specified accuracy, consider the following:
Erroneous parameters. Check that the calibration parameters are all correct
according to the Report of Test. If not, reprogram the constants. If the controller
does not keep the correct parameters, the memory backup battery may be
weak causing errors in data. See “Low Battery” in a previous solution.
Poor uniformity. There may be an actual difference between the bath’s control
probe and the reference thermometer due to excess gradients in the bath.
Check that the bath has an adequate amount of fluid in the tank and that the
stirrer is operating properly. Also check that the reference thermometer and
control probe are both fully inserted into the bath to minimize temperature gradi
ent errors.
Defective control probe. Check that the control probe has not been struck,
bent, or damaged. Refer to the previous solution for how to check the probe’s
resistance.
If the bath does not achieve the expected degree of temperature stability when
measured using a thermometer, consider the following:
Wrong proportional band setting. If the proportional band is set too narrow,
the bath will oscillate causing poor stability. In this case, increase the width of
the proportional band.
14 Troubleshooting
Troubleshooting
-
-
The controller alternately
heats for a while then
cools
The bath does not
achieve low temperatures
If the proportional band setting is too wide, the long-term stability of the bath is
affected. In this case decrease the width of the band. (Refer to Section 9.7.)
Bath fluid is too thick. Make sure that the bath fluid used is less than 50 centiStokes (10 is ideal) at the temperature at which the bath is controlling. Check
the fluid manufacturer’s specifications.
You should also change the bath fluid regularly and if it changes colors or be
comes too thick.
Defective control probe. Check that the control probe has not been struck,
bent, or damaged. Refer to the previous solution for how to check the probe’s
resistance.
Wrong proportional band setting. If the proportional band is set too narrow,
the bath will oscillate between too much heating and too much cooling causing
instability. Increase the width of the proportional band until the temperature sta
bilizes. (Refer to Section 9.7.)
Insufficient cooling. This may be caused by lack of refrigerant because of a
leak in the system. Refer to Section 12, Charging Instructions.
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7312 TPW Maintenance Bath
User’s Guide
Problem Causes and Solutions
The controller does not
maintain controller pa
rameters or parameters
are reset each time the
power to the unit is
removed
14.2 Comments
Note: Before performing the memory check,you need to record the controller
-
calibration parameters (found in the CAL menu of the instrument) and any
user-adjusted parameters that you have changed (such as the programmable
set points and proportional band).
Memory Check
Doing a memory check is the easiest way to verify the ability of the battery to
maintain controller parameters.
1. Power off the instrument.
2. Disconnect the instrument from AC power for 10 seconds.
3. Reconnect the AC power and power on the instrument.
4. If the display shows InIT and/or the cycle count shows a low number such as
0002, the battery is spent and should be replaced. Contact an Authorized Service Center for assistance.
5. After replacing the battery, you must reprogram the calibration and user-adjustable parameters into the controller.
14.2.1 EMC Directive
Hart Scientifics’ equipment has been tested to meet the European Electromagnetic Compatibility Directive (EMC Directive, 89/336/EEC). The Declaration
of Conformity for your instrument lists the specific standards to which the unit
was tested.
14.2.2 Low Voltage Directive (Safety)
In order to comply with the European Low Voltage Directive (73/23/EEC),
Hart Scientific equipment has been designed to meet the IEC 1010-1 (EN
61010-1) and the IEC 1010-2-010 (EN 61010-2-010) standards.
78
Via Acquanera, 29 22100 Como
tel. 031.526.566 (r.a.) fax 031.507.984
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