Why Does My NI-9237 with 9944/9945 return a constant data value?

Updated Mar 1, 2018

Reported In

Hardware

  • NI-9237
  • NI-9945
  • NI-9944
  • cDAQ-9171

Driver

  • NI-DAQmx

Operating System

  • Windows

Issue Details

When I have my NI-9237 hooked up to a quarter bridge completion accessory, the signal is a straight line. I would expect it to be noisy, but it's a solid horizontal line at the max amplitude. I followed the directions from the Configuring the NI 9944 or NI 9945 with the NI 9237 document, but I'm still having issues. What could be wrong?

Solution

This is likely due to a mismatch in the resistance of your strain gauge and the resistance of the completion accessory. The NI 9944 and 9945 have 120ohm and 350ohm resistances respectively. You must use the accessory that has the same resistance as your strain guage. 

To measure the resistance of your strain gauge, disconnect the gauge from the circuit and measure with your DMM.

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