PXI-6071e drifting offset on analog inputs

[pwb2103]

Hi, I have three PXI-6071E cards sitting in a PXI-1042 Chassis controlled by a computer with windows XP.  The 6071Es are connected to SCB-100 break out boxes which are wired to a pannel of BNC female panel mounts via twisted pairs.

I've noticed that all of my analog inputs will drift around from -10 V to +10 V if they are not connected to anything forcing them to a certain voltage.  This has always happened.  We also see quite a bit of cross talk between channels.  For example if I open a test pannel in the measurement and automation explorer I can watch the voltage read on the inputs drift through their full range, and altering signals on nearby channels will show up on the channel I'm measuring. 

Is this just standard behavior and to be expected?  Is there something more I could be doing to minimize this drift and cross talk?  I'm trying to reduce noise in my system so I figure optimizing my DAQ couldn't hurt.

Thanks

[AnalogKid2DigitalMan · Accepted solution]

With nothing connected to the high impedance inputs, the drift you see is perfectly normal. The front end to the circuitry is building up a charge, the cross-talk is proabably due to the input multiplexer (did not verifiy but I think the 6071 has one) transferring the charge to the other channels when they are scanned.

Search the forum for ghosting, you'll find related discussions.

-AK2DM

[pwb2103]

Thank you. I didn't realize ghosting was the name I was looking for.  Glad to know this is all standard.

After the search you recommended I was able to dig up this article:

http://digital.ni.com/public.nsf/allkb/73CB0FB296814E2286256FFD00028DDF