Resistive NI SWITCH Module Measures Different Values Across Polarity

Updated Jun 20, 2023

Reported In

Hardware

  • PXI-2722
  • PXIe-4081

Issue Details

I am measuring a simple resistor using NI PXI-2722 and NI PXIe-4081. I realized that the value measured is different when the resistor is measured across two different polarity. What causes this behavior?

Solution

Generally, this behavior is expected across resistive switches/ relay. This behavior is caused by the thermal emf and offset voltage. 

When measuring across polarity, the configuration is lead to typical channel accuracy and the accuracy is ~1% across channels in either polarity.

Additional Information

Do take account for thermal emf while measuring with resistive NI SWITCH module and NI DMM or replace the resistive NI SWITCH module into a non-resistive NI SWITCH module.

Related Links

Thermal EMF and Offset Voltage

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