Noisy Channel on PCI-6031E

[Greg AA]

Hello All,

I'm using a PCI-6031E for an application with multiple analog inputs that are typically in the +/-10VDC range.  On one particular channel, when I apply approx -9VDC to the channel, a lot of "noise" will appear (what seems like as much as +/-0.5V).  The noise is visible within my LabVIEW application, and can be verified with a scope.  The interesting thing is that the noise disappears if I stop scanning all DAQ channels and read only the channel of interest.  Likewise, if I move the signal to a different channel the noise disappears, even when scanning.  Finally, I can typically make the noise disappear by merely disconnecting and reconnecting the source.  Any thoughts as to what to explore?  Has anyone encountered anything similar?

[Josh_B1]

Hi Greg,

Could you do a FFT and see what frequency the noise is at.

Regards,

Josh Brown

[Josh_B1]

Hi Greg,

I have some more questions/suggestions. Do you have your channel connected single-ended or differentially. Refer to table 1 in this knowledge based article if you need to.

https://www.ni.com/en/shop/data-acquisition/measurement-fundamentals/field-wiring-and-noise-consider...

Also, have you tried connecting a battery to the bad channel? If not could you do so and report back what you see. If the battery gives you a bad signal then this may suggest a bad channel. 

Regards,

Josh Brown

[Greg AA]

Sorry that I forgot these important details...

-FFT shows the frequency to be in the MHz range

-Configuration is NRSE

I have two seperate identical systems that both exhibit the same issue on the same channel- thus I think a bad channel is not likely.

Thanks!

Greg

[Josh_B1]

Hi Greg,

Could you try configuring the system in the differential format and see if the noise still exist?

Regards,

Josh Brown