The following information is for the EMANT300

Measure Multiple Thermistors

In the application note on thermistor, we have used the current source in order to measure the resistance of the thermistor. Fortunately it is possible to use the EMANT300 USB DAQ to measure up to 6 thermistors just by using one current source. We do that by connecting the thermistors in series. (The method applies to resistance measurements and other resistive sensors like RTDs).

The schematic shows 5 thermistors and one reference resistance with 1% accuracy. By using the reference resistor, the thermistor resistance is given by

which eliminates any errors introduced by the current source.

We are able to measure up to 6 thermistors because the differential inputs of the EMANT300 USB DAQ, unlike most other DAQ modules, do not have fixed differential input pairs.

Note that you must ensure that the voltage at the IDAC does not exceed the compliance voltage which is 3.5V. In our example circuit, we set the current source to 12uA.