PCI-6229 60Hz noise and drifting voltage

[drevniok]

I am having some issues with a PCI-6229 DAQ connected via a CB-68LP.  I am running Labview8.6.1. 

The problem is with all of the analog inputs. There appears to be some kind of noice in the signal, and I cannot determine a reason for it. As it stands, I don't have anything connected to the computer other than the CB-68LP.  This connector block and DAQ have been know (in the past month) to function properly.  

The problem is that any signal appears to have a large (1V_pp @ 60Hz) noise on top of it.  So if I check the reading on an analog input channel with no connection there will simply be a sine wave a 60Hz going 1Vpp.  Additionally, the sine wave drifts alot (a DC offset), usually settling at about -6V.   I just can't come up with a good reason for this.  The input will read in another signal (from the same DAQ board, or even from an external function generator) and that reading will simply look like (InputSignal + 60Hz noise + DC offset).  

I have run the diagnostic tool (version 2.0) and everything seemed to have passed that test, but I am not sure if that means anything.  Essentially, the board seems to work, but there is a large noise signal along the way.   I have a hard time thinking it could be a result of a connection between the DAQ and the Connector block. 

I have everything set up in differential mode, and I am quite confident in the wiring between the block and the BNCs to which the block is attached.

I have included what labview reads from AI0 when 1. nothing is attached 2.  5.75V_pp @ 360Hz square wave is input.  I have also included the output from the diagnostic test.

Cheers,

-ben

[Scott-M]

Hi Ben,

It sounds like you have been going through the right trouble shooting steps, there are a few more things I would try to help you isolate your issue. First instead of reading the data in LabVIEW I would use the test panels in Measurement & Automation Explorer, this will help remove programming from the equation. Second, I would try using a different PCI slot as well as a different computer, this should help us remove any possible computer problems. At this point if the sine wave is still present, you might have to look into having the card sent to us to be fixed. You can reach us at 1-866-ASK-MYNI.

Let us know what you find.

Thanks

Scott M.

[drevniok]

Hello Scott,

Thanks for the reply.  I think I have fixed the issue.  After I posted the message I went ahead and switched PCI slots, that seems to have helped.  I also rewired the connector block, just in case.

Thanks for the suggestions. The card (fingers crosses) seems to be working well now.

Cheers,

-Ben

[Scott-M · Accepted solution]

That's awesome Ben,

If you have any noise issues in the future the following Developer Zone article has some really good information, just FYI.

Field Wiring and Noise Considerations for Analog Signals

Good luck with your application.

Scott M.