ILX Lightwave LDC-3700 Series User Manual

Thermsitor Voltape vs. Resolution for Various Temperatures
Temperature Voltage at 10
rrA Resolution
-20°C 56 mVI0C
0.018"C/mV
25OC
4.4 rn~k 0.23°C/mV
50°C
1.4 mVI0C 0.70°C/mV
Table
B.3 10K Thermsitor Voltage vs Resolution
For this thermistor, a temperature change from -20 to -lg°C will
be represented by 737 AID steps (if supplied with
10
PA). The same thermistor will only change about 18 .AD steps from 49 to 50°C!
The resolution you choose will impact the temperature displayed on the LDC-3700 Series Laser Diode Controller.
If you want to read a certain temperature with 0.2OC accuracy, you must set the LDC-3700 Series Laser Diode
Controller SENSOR SELECT switch for
that resolution. Since the thermistor is non-linear the resolution will also
decrease as the temperature increases. The high temperature limit occurs when the temperature resolution drops
below an acceptable level.
Selecting the Sensing Current
To select the current setting for a typical 10K thermistor, determine the lowest temperature you will need to sample
and set the SENSOR SELECT switch according to
the range limits in Table B.2. If the temperature you want to
sample is below 10 "C you will probably need to set the switch to the
10 pA setting.
W~th the SENSOR SELECT switch set to 10
pA, the best resolution you will see will be a O.l°C temperature
change
If, for example, the lower limit is 10°C you can choose either SENSOR SELECT setting, but there is a
tradeoff ~n terms of resolution.
If you need better than O.l°C measurement resolution you will have to change the
settmg of the SENSOR SELECT switch to 100
pA. If the lowei limit of the desired temperature range is less than
I0 "C. 2nd ! ou requlre resolution bener than 0.1 "C, try a lOOK thermistor on the 10 @ setting.
If you require temperatures of 10 "C to 30 OC, either SENSOR SELECT setting (100 pA or 10 FA) will work with
a
10K themlistor. However, the 100 pA setting provides greater measurement resolution, and therefore better
control
NOTE - Generally, it is best to use the 100 pA SENSOR SELECT setting for all
measurements of
10 "C or greater with a typical 10 K thermistor.
Selecting
and Using Thermistors
The hpe of thermistor you choose will depend primarily on the operatirig temperature range. These guidelines for
selecting the range and resolution will apply
to any thermistor. From Figure B. 1 you can see that 10 K thermistors
are generally a good choice for most laser diode applications where high stability is required near room
temperatures. Similarly, 10
K thermistors are often a good choice for detector cooling applications where you want
to operate at temperatures from -40°C to room temperature.
If you require a different temperature range or the accuracy you need can't be achieved with either switch setting,
select another thermistor. Thermistor temperature curves, supplied by the manufacture, show the resistance verses
temperature range for many other thermistors.
ILX Lightwave Corporation will also offer help for your specific
application.
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ILX Lightwave LDC-3700 Series Specifications

General

Brand	ILX Lightwave
Model	LDC-3700 Series
Category	Controller
Language	English