Signal Conditioning Requirements for Thermistors and RTDs

Thermistors and RTDs require the following signal conditioning:

Current Excitation—Because RTDs and thermistors are resistive devices, your DAQ system must provide a current excitation source to measure a voltage across the device. This current source must be constant and precise.

2-, 3-, and 4-Wire Configurations (RTDs only)—RTDs come in 2-, 3-, and 4-wire configurations. Therefore, your system must support the type of RTD you choose. Thermistors are typically 2-wire devices because they have higher resistance characteristics, thus eliminating lead resistance considerations.

Linearization—Neither RTD nor thermistor output voltage is linear with temperature. Therefore, your system must perform linearization either in hardware or software.