We are having random noise issues on PC controlled data acquisition where one is related to VFD drive which is controlling the AC motor.
The thing is that, sometimes we observe continous large noise around 0.3V and right now I cannot say the nature of the noise. But when the VFD is switched OFF the noise disappeared and when turned ON it appeared again for 5 seconds and disappeared in 10 seconds. This is strange becuase it is somehow VFD realted but also doesnt appear all the time.
About 12 meters far away we have a data-acquisition computer with various DC inputs and the daq board also controls the VFD through an isolation amplifier. All input signals are floating, so no ground loop. VFD ground is isolated from the daq side but my guess is somehow VFD's switching noise might be injecting noise to power lines.
If this noise is VFD related my question is:
If I daisy chain some electrical power outlets and power all the daq system(PC, transducers. power supplies) thhrough the same outlet. And if I also use a filter such as this one after the mains outlet, would that be worth to try? This filter says it can filter both common mode and differential mode signals. Or should I first find the FFT of the noise and then find a filter?