DMM Reading Returns NaN in Auto Range Mode

Updated Jul 24, 2018

Reported In

Hardware

  • PXI-4065

Driver

  • NI-DMM

Issue Details

I have a DMM measuring various things, such as DC voltages and resistance measurements, in Auto Range mode and intermittently get NaN.

Solution

Auto Range switches through ranges and finds the best one for the current measurement it is checking. NaN indicates over range. If the device Auto Ranges to a single range and is used for multiple measurements, but the signal rises outside of that range, the DMM will return NaN. 

Simplest solution:
  • Evaluate the values to be expected (if reading multiple voltages, know the values of those voltages)
  • Set range to the largest voltage expected
The caveat to this is less accuracy. The larger the voltage range, the lower the resolution of the measured signal.

Modular solution:

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