Solution
These modules do not officially support 2-Wire RTD measurements, since no accuracy for two wire RTD measurements are provided. It is important to remember that 2-Wire RTD measurements will be significantly less accurate than 4-Wire or 3-Wire RTD measurements because the module does not internally compensate for lead resistance.
The following diagram shows how to connect a 2-Wire RTD to a NI 9216, NI 9217, and NI 9226. Connect the sensor to
RTD+ and
RTD- and then place a jumper between
RTD- and
COM. The module has the ability to internally connect
RTD+ to
4-Wire EX.
Note: Since you are using three terminals on the front of the NI 9217, you must configure your DAQmx Task for a 3-Wire RTD configuration.
The following diagram shows how to connect a 2-Wire RTD to an NI 9219. Connect the sensor to HI and LO and then place a jumper between EX+ to HI and LO to EX-.
Note: Since you are using four terminals on the front of the NI 9219, you must configure your DAQmx Task for a 4-Wire RTD configuration.
The NI 9219 channels can be configured for 2-Wire resistance mode and the scaling from resistance to temperature can be performed in software.