When COM is floating, the internal common-mode voltage of the
input circuitry is the average of all the inputs.
Note
When two or more thermocouples are referenced
to different common-mode voltages, connect COM to a
common-mode voltage reference that is within ±1.2 V
of the common-mode voltages of all thermocouple
inputs.
NI 9214 Connection Guidelines
• Make sure that devices you connect to the NI 9214 are
compatible with the module specifications.
• The shield grounding methodology can vary depending on
the application.
• Refer to your thermocouple documentation or the
thermocouple wire spool to determine which wire is the
positive lead and which wire is the negative lead.
Minimizing Thermal Gradients
Changes in the ambient air temperature near the front connector
or a thermocouple wire conducting heat directly to terminal
junctions can cause thermal gradients. Observe the following
NI 9214 Getting Started Guide
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© National Instruments
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