2-Wire RTD Support For NI 9216, NI 9217, NI 9226, and NI 9219

Updated Oct 8, 2018

Reported In

Hardware

  • NI-9216
  • NI-9217
  • NI-9226
  • NI-9219

Issue Details

The Operating Instructions for the NI 9216, NI 9217, NI 9226, and NI 9219 explain how to connect and measure from a 4-Wire RTD and 3-Wire RTD. Do these modules also support 2-Wire RTDs?

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.

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