Connecting A Thermistor - THORLABS ITC502 Operation Manual

1.9 Connecting components
The TEC element and the temperature sensor are to be connected according to the
shown pin assignment with shielded cables to the output jack at the rear of the
ITC5xx.
The shielding of the cable has to be put on ground potential (pin 13,14,15).

1.9.3 Connecting a thermistor

The thermistor is set up between pin 3 and pin 4. The polarity is unimportant if the
thermistor is floating. If one pin of the thermistor is grounded (for example in a laser
module), this pin has to be connected to pin 3.
Using a thermistor, all temperatures are shown in ohms, therefore you have to look
for the corresponding temperature in the datasheet of the thermistor.
Figure 5 Connecting a thermistor
When the actual temperature "T " is chosen for display the thermistor resistance is
ACT
shown. The DIP switches (SW7, SW8, Figure 2) select the resistance range of the
thermistor, see 1.8.4 "DIP switch for "wake up" preset". In position "TH < 20 kΩ" the
maximum thermistor range is 20 kΩ and the measurement current 100 µA. In
position "TH < 200 kΩ" the maximum thermistor resistance is 200 kΩ and the
measurement current 10 µA.
The dependency of resistance on temperature and vice versa of an NTC-thermistor
is described by the formula:
ITC500 / page 23