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Open channel voltage jumps from + to - 10 Volts

Setup:

cDAQ NI-9189

NI AO 9264

NI AI 9209

NI DI/DO 9375

 

Project:

Design a VI for a Dynomometer that shows raw voltage and calibrated values live for RPM, Torque, Thrust, Cylinder Head Temps, and Fuel Flowrate of an Engine. Save this data to a .csv file for later analysis.

 

Problem:

Something has caused the voltages of the cDAQ to jump randomly between +10 and -10V. This isn't happening on the USB DAQ we are using and didn't occur before a few weeks ago. Reverting to an old version of the VI didn't fix it, but nothing has changed with the setup.

 

Explanation:

As shown in the attached image, in which the top image shows an unconnected RSE channel, the second image shows an unconnected Differential channel, and the third image shows what happens to a connected channel regardless of the setting used. I apologize for the messy state of the VI, due to the functionality we need and our relatively limited experience with LabView it isn't pretty, but this was the easier way to make it. If there is any advice that could be offered to fix this issue it would be greatly appreciated.

 

 

Edit: Since I use Labview 2020 I added a 2015 LabView Version as well.

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Message 1 of 2
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It sounds like you have a hardware problem not a software problem.

 

Don't read disconnected channels.

 

OR

 

Short the disconnected input channel to ground.

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