Faulty NI Module or Improper Grounding?

[KurtzC1]

Hello Everyone!

So I am using a NI-9189 ethernet chassis with a NI 9205, and I have been having serious trouble reducing noise and getting a good analog signal. The noise is so extreme that literally clapping your hands next to the NI9205 is enough cause disturbance. I am working in a conex box test facility and I am running data through a 200ft ethernet chord. Initially I thought it was broken pressure transducers, so wired a 9V DC battery into channel 0 as a constant analog signal. This did not solve the problem. Not only did channel 0 not read 9V, but it also changed the voltage of adjacent channels.

Things I have tried.

• Powering the NI 9189 from an AC wall outlet and not a switching power supply
• Grounding the chassis with the grounding screw to the power supply
• Grounding the chassis with the grounding screw to the AC outlet
• Tying the chassis ground and the NI 9205 ground together and grounding them both to the AC outlet.
• Switching the NI 9205 into different slots of the chassis

Potential Solutions

1. I don’t have an earth grounding rod next to my facility, but I could maybe make one. I know the manufactures guide of the NI 9189 recommends an Earth ground. Although I have used other NI chassis before, and I didn’t need an earth ground. Why would I need one now?
2. Maybe there are grounding loops in the system? I don’t even know how to tell if there are ground loops.
3. Maybe the NI 9205 is damaged?

Any help would be appreciated.

Thanks

[LennartM]

Are you measuring differential or single ended? Probably single ended? How did you connect the battery? Can you check of the ground of the module is connected to the ground of the power supply? Maybe the connector isn't making fully contact with the card. And what kind of power supply do you use? 

Do you have any filters placed before the NI-9205? 

[KurtzC1 · Accepted solution]

Hi Everyone!

So it turned out to be two issues. The first issue was that the harness which was connected to the NI9205 was wired wrong. The second issue was that RSE was not defined in the task. It was set to Default in the polymorphic VI. One thing I learned was that you can use NIMax to directly measure the voltage going into the card. This worked wonders trying to troubleshoot the issue.