PXIe-4331 Gain Factor 2.5?

[Amy4082001]

Hi, I'm trying to use the PXIe-4331 to measure a wheatstone bridge.  I noticed that when my bridge has resistors in the 10kOhm's range, the differential output voltage measured with the PXIe-4331 is always 2.5x higher than the output voltage measured using an external multimeter. 

I also used a wheatstone bridge that has resistors in the 1MOhm's range, and I'm still seeing this 2.5x gain.  So, the issue isn't loading.

Am I doing something wrong? Is the PXIe-4331 not calibrated correctly (if so, how to do that)? Thanks.

[BrinkHombre]

Hello Amy4082001,

1. What strain gauge configuration is your device setup in, quarter, half or full?
2. Where are you taking your measurements from, NI MAX, LabVIEW, or another SW?
   • Also, can you confirm the DAQ reading is incorrect with an oscilloscope or DMM?
3. Have you taken a look at the PXIe-4331 User Manual to confirm your connections are correct?

Best regards,

[Amy4082001]

Hi Ryan,

1)  Full Bridge

2)  I've taken my measurements using the NI test panel (see pxie4331_test_panel.jpg). I also have my own Labview code (see pxie4331_labview_block_diagram.jpg; if you want the VI I could send that).  Both are reporting the same value.  

I've confirmed the readings with two different DMMs.  Both DMMs are reporting the same value, which is usually 2.5x more than what the Test Panel or my VI is reporting. 

3) I connected wires out of the PXIe a lot time ago so I'll have to take a look.  

[Niki.B]

Hello,

As Ryan mentioned, I would double check that the device is connected correctly for the type of Full Bridge configuration you are using for your measurement.

Also, here is the calibration procedure for the PXI-4331 if the device ends up needing to be calibrated.