There are different ways in which you can do Thermistor measurements using C series modules:
Use case: For medium resistance thermistors (less than 10 kΩ)
The NI-9219 can be used for thermistor measurements, although this is not a recommended configuration. The module was not specifically designed for thermistor measurements so there may be limitations affecting measurements accuracy. This is because it was never tested with thermistors and the accuracy hasn't been characterized across the entire possible thermistor range. There are two configurations for measuring a thermistor with the NI-9219:
Setting the NI-9219 to 2-wire 10 kΩ resistance mode will return a resistance measurement that can be scaled to temperature using the thermistor's scaling coefficients.
If using this configuration, keep in mind the following limitations:
For more information on how to make thermistor measurements using the half-bridge configuration, please refer to the Measuring Thermistors in a Half-Bridge Configuration with the NI-9219 Example. The 2-wire resistance measurement configuration is easier to assemble than the half-bridge configuration, but it does not take into account measurement accuracy.
Use case: For small resistance thermistors (less than 4 kΩ)
Follow the guide Making an RTD or Thermistor Measurement in LabVIEW to use an RTD module to measure your Thermistor. Please check the Resistance Measurement Range to make sure the card is capable of measuring your sensor's resistance range.
Many thermistors have a sensitivity of 3-6% per °C which means that they may vary in resistance by more than ±500% of their nominal value over their full measurement range. This wide range presents a measurement challenge that can be addressed by making a half bridge measurement with a correctly chosen reference resistor and a Strain/Bridge Input Module. For more information on how to make thermistor measurements using the half-bridge configuration, please refer to the Measuring Thermistors in a Half-Bridge Configuration with the NI-9219 Example.
Use case: For large resistance thermistors (10 kΩ and higher)
A Voltage Input module can help you measure sensors that operate changing their resistance, such as Thermistors. There are some strategies you can take, depending on the characteristics of the circuit you are designing:
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