ILX Lightwave LDC-3916558 User manual

User’s Guide
3A Current Source TE Module
LDC-3916558
ILX Lightwave Corporation · P. O. Box 6310 · Bozeman, MT, U.S.A.59771 · U.S. & Canada: 1-800-459-9459 · International Inquiries: 406-556-2481 · Fax [phone]
ilx.custhelp.com ·www.ilxlightwave.com
70033202 June 2005

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TABLE OF CONTENTS
Table of Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i
Safety and Warranty Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v
Safety Information and the Manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v
General Safety Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v
Safety Symbols. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi
Safety Marking Symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi
Warranty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii
Comments, Suggestions, and Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix
Chapter 1 Introduction and Specifications
Product Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Initial Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Installing the Module into the LDC-3916 or LDC-3908 Mainframe . . . . . . . . . 2
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Chapter 2 Operations
Connecting to the Temperature Controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
TEC Grounding Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Operating the Temperature Controllers from the Front Panel . . . . . . . . . . . . 7
General Front Panel Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Example Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Choosing Control Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Setting Gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Setting Sensor Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

TABLE OF CONTENTS
ii LDC-3916558
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Setting Safety Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Default Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
TEC Error Indicators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Chapter 3 Remote Operations
Remote Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
LDC-3916558 3-AMP Temperature Control Module Command Set . . . . . . 19
LDC-3916558 3-Amp Temperature Controller Often Used Commands . . . . 21
Command Timing and Completion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Status Reporting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Status Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Output Off Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Error Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Chapter 4 Command Reference
GPIB Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
LDC-3916558 Device-Dependent Commands . . . . . . . . . . . . . . . . . . . . . . . . . 33
Chapter 5 Troubleshooting
Calibration Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
Recommended Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
Local Calibration of the 3916558 3-Amp Temperature Controllers . . . . . . . . 69
Thermistor Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
ITE Current Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
TE Voltage Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
Remote Calibration of the 3916558 3-Amp Temperature Controllers . . . . . . 72
Thermistor Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
ITE Current Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
TE Voltage Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
Troubleshooting Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

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LIST OF FIGURES
Figure 2.1 Rear Panel TEC Connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
Figure 2.2 3916 Front Panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
Figure 2.3 Channel Menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
Figure 2.4 TEC p1 Menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
Figure 2.5 TEC p2 Menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
Figure 2.6 TEC p3 Menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
Figure 2.7 TEC p4 Menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
Figure 2.8 Example Thermistor Resistance vs. Temperature . . . . . . . . . . . . . . . . . .14
Figure 3.1 LDC-3916558 3-Amp Temperature Controller Command Path Structure20
Figure 3.2 LDC-3916558 Status Condition Registers . . . . . . . . . . . . . . . . . . . . . . . .23
Figure 3.3 LDC-3916558 Event Status Registers . . . . . . . . . . . . . . . . . . . . . . . . . . .24
Figure 4.1 Command Description Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33

LIST OF FIGURES
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LIST OF TABLES
Table 2.1 TEC Controllable Laser Sources . . . . . . . . . . . . . . . . . . . . . . . . . 11
Table 2.2 3916558 Default Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Table 2.3 TEC Error Indicators. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Table 3.1 LDC-3916558 Often Used Commands. . . . . . . . . . . . . . . . . . . . . 21
Table 3.2 LDC-3916558 TEC Output Off Register Contents . . . . . . . . . . . . 25
Table 4.1 LDC-3916 Device-Dependent Commands. . . . . . . . . . . . . . . . . . 30
Table 5.1 Recommended Test Equipment. . . . . . . . . . . . . . . . . . . . . . . . . . 68
Table 5.2 Required Calibration Components . . . . . . . . . . . . . . . . . . . . . . . . 68

LIST OF TABLES
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CHAPTER 1
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INTRODUCTION AND SPECIFICATIONS
This chapter is an introduction to the LDC-3916558 3-Amp Temperature Control
Module for the LDC-3916 or LDC-3908 Laser Diode Controller Mainframe. It
contains unpacking information, instructions on how to install and apply power,
and safety considerations and instructions. It also contains some maintenance
information and specifications.
If any of the following symptoms exist, or are even suspected, remove the LDC-3916558
Module from service. Do not use the module until trained service personnel can verify
safe operation.
Visible damage
Severe transport stress
Prolonged storage under adverse conditions
Failure to perform intended measurements or functions
If necessary, return modules to ILX Lightwave for service and repair to ensure that safety
features are maintained.
Product Overview
The 3916558 module is intended to be used within a LDC-3916 16-channel or
LDC-3908 8-Channel Laser Diode Controller Mainframe. The module contains a
single three ampere independent temperature controller that drives a
thermoelectric cooler (TEC). The temperature controller features a bi-polar
current driver that works with most TEC modules to deliver precise temperature
control over a wide range of temperatures. The temperature controller operates
using thermistor type temperature sensors only. The LDC-3916558 features a

INTRODUCTION AND SPECIFICATIONS
Installing the Module into the LDC-3916 or LDC-3908 Mainframe
2 LDC-3916558
CHAPTER 1
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TEC module voltage measurement, selection of thermistor current range, and
control loop gain adjustment from 1 to 127.
Initial Inspection
When you receive your LDC-3916558 3-Amp Temperature Control Module, check
for shipping damage immediately. Verify that the module has an ESD protective
hood on the 15-pin D-sub and that it is enclosed in an ESD safe handling bag.
Remember before handling the module to follow proper ESD safe handling
procedures.
Installing the Module into the LDC-3916 or LDC-3908
Mainframe
If you are receiving this new module without an LDC-3916 or LDC-3908
Mainframe for installation into a previously purchased mainframe, follow the
instructions below. If your system was configured at the factory with your desired
modules, skip this section.
Static discharge can damage your new Temperature Controller Module. Be certain you
use proper grounding procedures before you unpack and install your module(s) into the
LDC-3916 or LDC-3908 Mainframe.
Inspect the module for any visible shipping damage that may have occurred before
inserting the module into the mainframe. Pay special attention to the copper shielding
material on the back edge of the module.
Be sure that the LDC-3916 or LDC-3908 Mainframe power is off before inserting or
removing any module.
Unwrap the module from the anti-static bag it was packaged in.
Make sure the instrument the module is going into, either the LDC-3916 or the
LDC-3908, is switched off. Insert the module into the desired slot from the rear.
Each module is supported by two plastic card guides inside of the mainframe.
Insert the module, 40-pin connector first, by lining up the edges of the module
frame with the appropriate card guides (one on top and one on the bottom).
Carefully slide the module into the mainframe slot until the connector is seated.
You will have to push a little harder to seat the module. The rear panel of the
module should be flush with the mainframe when properly inserted. Fasten the
module to the mainframe with two screws located at the top and bottom of the
module rear panel.

INTRODUCTION AND SPECIFICATIONS
Specifications
08_05 LDC-3916558 3
CHAPTER 1
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Specifications
Temperature Control1
Temperature Control Range2:-99
oC to 150oC
Thermistor Setpoint (Resolution and Accuracy)3
-20oC to 20oC0.1
oC; +0.2oC
20oC to 50oC0.2
oC; +0.2oC
Short Term Stability (1 hour)4:<+0.007oC
Long Term Stability (24 hours)5:<+0.01oC
Output Type: Bipolar current source
Compliance Voltage: 8 VDC
Maximum Output Current: 3 A
Maximum Output Power: 24 W
Current Noise and Ripple6: <2 mA rms
Current Limit Range: 0.1 to 3.10 A
Current Limit Set Accuracy: +0.05 A
Control Algorithm: Gain adjustable from 1 to 127
Temperature Sensor
Types: Thermistor (2-wire NTC)
Thermistor Sensing Current7: 10 uA/100 uA
Useable Thermistor Range: 25 to 450,000 Ωtypical
User Calibration: Steinhart-Hart, 3 constants
TEC Measurement (Display)
Temperature
Range8:-99.9
oC to 199.9oC
Accuracy: +0.5oC
Thermistor Resistance (10 uA setting)
Range: 0.01 to 450.00 kΩ
Accuracy9:+0.05 kΩ
Thermistor Resistance (100 uA setting)
Range: 0.001 to 45.000 kΩ
Accuracy10:+0.005 kΩ
TE Current Range: -3.00 to 3.00 A
TE Current Accuracy: +0.04 A

INTRODUCTION AND SPECIFICATIONS
Specifications
4 LDC-3916558
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1. All values relate to a one-hour warm-up period
2. Software limits of range. Actual range possible depends on the physical load, thermistor type, and TEC module used.
3. Accuracy figures are quoted for a typical 10kΩthermistor and 100 uA current setting for -5oC to 50oC, and a typical 10kΩthermistor
and a 10 uA current setting for -20oC to -5oC. Accuracy figures are relative to the calibration standard. Both resolution and accuracy
are dependent upon the user-defined configureation of the instrument.
4. Over any one-hour period, half-scale output, controlling an LDM-4412 mount @ 25oC, with 10kΩthermistor, on 100 uA setting.
5. Over any 24-hour period, half-scale output, controlling an LDM-4412 mount @ 25oC, with 10kΩthermistor, on 100 uA setting.
6. Measured at 2A output over a bandwidth of DC to 25 MHz.
7. Thermistor current software selectable by front panel or GPIB.
8. Software limits of display range.
9. Using a 100 kΩthermistor, controlling an LDM-4412 mount of -30oC to 25oC.
10.Using a 10 kΩthermistor, controlling an LDM-4412 mount over -5oC to 90oC
11.Voltage measurement accuracy while driving calibration load; accuracy is dependent upon load used.
In keeping with our commitment to continuous improvement, ILX Lightwave
reserved the right to change specifications without notice or liability for such
changes.
TE Current Resolution: +0.01 A
Voltage Range: -10.75 to 10.75 V
Voltage Resolution: 100 mV (1 mW through GPIB)
Voltage Accuracy11:+70 mV (+20 mV through GPIB)

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CHAPTER 2
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OPERATIONS
This chapter introduces you to the operation of the LDC-3916558 front panel
control functions. It shows you how to use the 3916558 to control a load
temperature. It also gives instructions for connecting a load to a temperature
controller's output. We recommend that you review the contents of this chapter at
a minimum before operating your new LDC-3916558 3-Amp Temperature Control
Module.
The 3916558 module contains a 3-Amp temperature controller.
The 3916558 is intended for use with Thermoelectric Cooler (TEC or Peltier)
modules.
Connecting to the Temperature Controller
Use the 15-pin connectors on the rear panel of your 3916558 module to make
connections to thermoelectric cooler (TEC) modules and their associated
thermistors. There are connections provided for current drive and temperature
sensor. Also provided are connections to earth ground (chassis) and to the
modules' analog ground. The pinout diagram for this connector is shown in Figure
2.1.

OPERATIONS
Connecting to the Temperature Controller
6 LDC-3916558
CHAPTER 2
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Figure 2.1 Rear Panel TEC Connector
Current will flow from pins 1 and 2 (connected internally) to pins 3 and 4 when the
controller is trying to cool the load. This is referred to as "positive" current.
Current will flow from pins 3 and 4 to pins 1 and 2 when the controller is trying to
heat the load. Pin 5 and 6 are connected to the LDC-3916 or LDC-3908 chassis,
which is connected to "earth ground." Sensor current (10 µA or 100 µA) flows
from pin 7 to pin 8; a voltage will develop across a thermistor connected to these
pins. Analog Ground is provided at pin 9 as a convenient reference when making
measurements or troubleshooting a system, but it is not normally required. Pins
10-15 are reserved by ILX Lightwave for diagnostic purposes and must not be
connected.
TEC Grounding Considerations
The TEC Module pins are isolated from chassis ground, allowing either output
terminal to be connected to earth ground at the user's option.
For the TEC connector, if any one terminal pin is grounded, then no other terminal pin
should be grounded. Do NOT connect Sensor (-) to TEC Module (- or +). Damage to the
instrument and devices will occur.
1
2
3
4
5
9
10
11
12
1,2 TE Module (+)
3,4 TE Module (-)
5,6 Earth Ground
7 Sensor (+)
8 Sensor (-)
9 Analog Ground
10 N/C
11 N/C
12 N/C
13 N/C
14 N/C
15 N/C
6
7
8
13
14
15

OPERATIONS
Operating the Temperature Controllers from the Front Panel
08_05 LDC-3916558 7
CHAPTER 2
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Operating the Temperature Controllers from the Front Panel
This section describes how to operate the LDC-3916558 3-Amp Temperature
Controller from the front panel of either the LDC-3916 or LDC-3908 mainframe. It
begins by reviewing the front panel operations and continues by showing you an
example. For a more detailed explanation of the front panel keys, see either the
LDC-3916 or LDC-3908 Mainframe manual.
General Front Panel Operation
Figure 2.2 3916 Front Panel
The two areas of interest on the front panel are the DISPLAY area and the
ADJUST area. The DISPLAY area contains the display screen and various keys
that allow you to select a menu and parameters within that menu.
The keys labeled F1, F2, F3, and F4 have several functions depending which
page is displayed. The boxed text on the right of the screen are the functions
associated with these softkeys. In the lower right corner of the DISPLAY area are
the UP (K) and DOWN (L) ARROW hardkeys. Most of the menus have adjustable
parameters. You adjust the parameters using the Kor Lhardkeys.
DEC
INC
Ï
Ð
ADJUST AREA
DISPLAY AREA
SOFTKEYS

OPERATIONS
Operating the Temperature Controllers from the Front Panel
8 LDC-3916558
CHAPTER 2
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The ADJUST section contains
keys used to adjust the value of
a parameter once selected. Set
the value of a parameter using
the numeric keypad (along with
the ENTER key), the ADJUST
knob, or the INC (K) and DEC (L)
keys in the lower left corner of
the ADJUST section.
Example Setup
The 3916558 temperature controller has four pages (menus) of information.
Suppose you need to maintain the temperature of a laser package at 15.5 °C .
Your laser is in a package that comes equipped with an internal TEC module and
a thermistor.
To set up the temperature controller:
•Select constant-temperature control mode
•Enter the temperature setpoint of 15.5 C
•Select the sensor current range
•Enter the appropriate thermistor constants
•Set the control loop gain
•Set appropriate high temperature limit and TEC module current limits.
To access any of the TEC information pages you must start with the "Channel"
menu. The most direct way is to press the CHAN key located directly below the
MAIN key in the upper right corner of the DISPLAY area.
The Channel menu allows you to change channels (modules) by rotating the
ADJUST knob, turn the temperature controllers on or off, and access each of the
TEC's menus. To get to the TEC's first menu,press the F2 softkey: it is "attached"
to the "TEC" box in the Channel menu. The next menu is the TEC page 1 menu.
Figure 2.3 Channel Menu
Figure 2.3 Display Area
Figure 2.3 Display Area

OPERATIONS
Operating the Temperature Controllers from the Front Panel
08_05 LDC-3916558 9
CHAPTER 2
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In the TEC page 1 menu, you can set the Temperature setpoint (TSet), the high
temperature limit (TLim), and the control mode (Mode). This page also displays
measured temperature (T), TE module current (I), and measured TEC module
voltage (V). You can also turn the controller on or off from this page.
To enter the temperature set point, press the Lhardkey until the TSet parameter is
highlighted. Enter 15.5 using the keypad, and press Enter. Note: whenever you
use the keypad to enter a parameter value, you must press Enter within three
seconds or the parameter will revert to its previous value. Now press the L
hardkey until the TLim parameter is highlighted. Enter 40.0 using the numeric
keypad. Now press the Lhardkey until the Mode parameter is highlighted. Press
the INC hardkey in the ADJUST area until "T" is displayed.
Figure 2.4 TEC p1 Menu
From the TEC page 1 menu, press the F4 softkey: it is attached to the "down-
arrow" box on the page 1 menu. Now you will see the TEC page 2 menu.
Figure 2.5 TEC p2 Menu
In the TEC page 2 menu, you can set the constant resistance setpoint, the
constant current setpoint, and the current limit. Press the Lhardkey until the ILim
parameter is highlighted. Enter 3.0 using the numeric keypad. The RSet
parameter is for constant resistance control mode, and the ISet parameter is for
constant current mode.

OPERATIONS
Operating the Temperature Controllers from the Front Panel
10 LDC-3916558
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Figure 2.6 TEC p3 Menu
In the TEC page 3 menu, press the hardkey until the Gain parameter is
highlighted. If you're not sure what the best gain setting should be, a safe first
choice is 30. If you want the controller to drive to the setpoint faster, enter a
higher value. For this example, enter the number 35. Now press the Lhardkey
until the Sensor parameter is highlighted. For now, press the INC hardkey in the
ADJUST area until 100 µA is displayed. The other parameters you can enter from
this page are the Steinhart-Hart coefficients for the particular thermistor that you
are using to measure temperature. If it's installed in a laser package, the
coefficients may be available in the package documentation. You can restore the
default values by pressing the F2 softkey. The defaults are approximate values for
the typical 10 kΩthermistor.
Figure 2.7 TEC p4 Menu
From the TEC page 3 menu, press the F4 softkey: it is attached to the "down-
arrow" box on the page 3 menu. Now you will see the TEC page 4 menu. In the
TEC page 4 menu, you can configure the TEC to turn off a laser current source in
a different channel that has any of the modules shown in Table 2.1. The TEC will
then turn off an external laser if the temperature limit is exceeded or if the TEC
fails in anyway. Highlight the Channel parameter and turn the knob (or press the
INC hardkey) to select the desired channel number, All to choose all channels, or
None so that the TEC will not turn off any laser current sources.

OPERATIONS
Operating the Temperature Controllers from the Front Panel
08_05 LDC-3916558 11
CHAPTER 2
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Note: The only channel numbers that will appear are channels in which a controllable laser
source resides. Next, highlight the Output parameter and turn the knob (or press the INC
hardkey) to select laser source output 1 or 2 (refer to Table 2.1), Both to choose both
outputs, or None so that the TEC will not turn off either laser current source output. In
modules with 2 laser sources, output 1 is the top source and output 2 is the bottom source.
Table 2.1 TEC Controllable Laser Sources
You are now finished setting up the TEC to control temperature to 15.5 C.
Connect the load and turn on the temperature controller. From any of the three
TEC pages p1, p2, p3 or p4, you can turn on the output by pressing the F1
softkey, associated with the "OFF" box in each page. Notice that the text inside
the box changes to "ON." The text box reports the controller's on/off status.
Note: To check the firmware version in any module, select the correct channel number in
the CHAN menu, then press the following keys in this order:
For information regarding firmware upgrades, contact ILX Customer Support.
3916 Module Firmware Version Number of
Laser Source
Outputs
3916371 v2.03 or greater 1
3916372 v2.03 or greater 1
3916374 v2.03 or greater 1
3916376 v2.03 or greater 1
3916332 v1.03 or greater 2
3916334 v1.03 or greater 2
3916336 v1.03 or greater 2
3916338 v1.06 or greater 1
+/ . Enter

OPERATIONS
Guidelines
12 LDC-3916558
CHAPTER 2
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Guidelines
This section presents some guidelines intended to assist you in selecting the
optimal settings for your application.
Choosing Control Mode
In the preceding example, you configured a controller to maintain a load at a
constant temperature. The 3916558 controller uses a thermistor to measure
temperature. A negative temperature coefficient (NTC) thermistor is a device
whose resistance decreases as its temperature increases. The sense-current that
the controller provides through the thermistor results in a voltage across the
thermistor. This voltage is used as a feedback signal by the 3916558's control
loop to maintain a constant temperature.
In both constant-temperature and constant-resistance modes, the quantity that is
maintained constant by the controller is the thermistor resistance. In constant
temperature mode, the 3916558 converts the temperature setpoint to a thermistor
resistance setpoint.
The 3916558 uses the Steinhart-Hart equation to convert a temperature to a
resistance. The equation describes the nonlinear resistance vs. temperature
characteristics of typical thermistors. Calibrating a thermistor consists of
measuring its resistance at various temperatures, and fitting these measured data
to the Steinhart-Hart equation. The resulting coefficients C1, C2, and C3
effectively describe the thermistor.
If you need to know the precise temperature of your load, you must use a
calibrated thermistor, and enter its Steinhart-Hart coefficients C1, C2, and C3 in
the page 3 menu. If the exact temperature is not crucial, you can use the default
constants provided by the 3916558. However, the 3916558's temperature
accuracy specifications apply only to a calibrated thermistor with C1, C2, and C3
entered.
In effect, constant temperature control mode is the same as constant resistance
mode, but the temperature setpoint TSet is converted to a resistance setpoint.
(RSet, the constant-resistance setpoint, is not affected by TSet.) If you prefer to
avoid that conversion, or if you do not know your thermistor's coefficients, but you
know the thermistor resistance at your desired operating point, then constant-
resistance mode is an option for you.
Another control mode that is available in the 3916558 is constant-current mode.
In general, the amount of heat a TEC module pumps depends on its drive current.
If you have a situation where a constant heat load must be removed or added,
then you might consider using constant current mode.