Thermocouples and Grounding on the NI 9214

Updated Apr 18, 2018

Reported In


  • NI-9214


  • NI-DAQmx

Issue Details

I have a thermocouple with a TC+ and TC- wire, but see that the NI 9214 has a COM ground pin. Do I need to wire anything into the COM pin?


For most applications, you do not need to connect COM. Connecting to COM is not necessary for the following configurations:
  • All thermocouples are floating.
  • All thermocouples are referenced to the same common-mode voltage.
  • One thermocouple is reference to a common-mode voltage and all other thermocouples are floating.

Additional Information

When COM is floating, the internal common-mode voltage of the input circuitry is the average of all the inputs.