Bias Resistors For Floating Source Measurement

Updated May 24, 2018

Reported In

Hardware

  • NI-9238
  • NI-9239
  • C Series Universal Analog Input Module

Issue Details

I am taking a floating source measurement using an NI data acquisition device. However the obtained signal is incorrect/unexpected. Do I require bias resistors for this kind of measurement to measure my signal correctly?

Solution

Yes it is recommended that you use bias resistors to ensure your measurement is taken correctly. Depending on your wiring configuration, the correct bias resistor wiring is shown in the diagram below:

Additional Information

For more information on wiring for floating source measurements and bias resistor specifications see Field Wiring and Noise Considerations for Analog Signals under section  3. Measuring Floating (Nonreferenced) Sources.

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