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I am trying to measure the strain on a part using a strain gauge. The gauge is a 120 $\Omega$ strain gauge from HBM. I am using National Instruments (NI) hardware and LabVIEW software to capture the strain measurements. The gauge is connected to a cDAQ 9237 using a NI 9944 bridge. The software has been tested previously and it worked, but I think there is some problem with the hardware. Once the gauge is connected to the bridge and a current runs through it,I can only read a flat curve at 0.025 V, which translates to aproximately 5% strain.

But if I instead unplug the strain gauge from the bridge, there is a measured noise, which suggests that a current runs through the bridge and in turn is measurable. I think there is a problem in either the calibration or the gauge itself. No matter how much I compress the material, there is no change in the measured current, it remains flat. Ideally the current would change once the material is exposed to a strain. My question is if anyone has encountered anything similar and or know how to make it work?

Edit: When I try to calibrate the strain gauge, I recieve the following error code: enter image description here

Regarding the configuration, I use the following quarter bridge setup: enter image description here

The strain is measured over R4.

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  • $\begingroup$ So what was your gauge calibration? Or bridge calibration? Are you sure you have it all connected correctly? You should show the diagram. $\endgroup$
    – Solar Mike
    Oct 18 '21 at 13:36
  • $\begingroup$ I made an edit where I added the bridge schematic and error code which I recieve when I try to calibrate the strain gauge using the NI MAX software. $\endgroup$ Oct 19 '21 at 10:53

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