With > 1 grounded source, are there ground loops in NRSE?

[Mike Saginaw]

I understand that when one grounded source is connected to LabView in NRSE configuration, there are no ground loops;
and that this is consistent with the recommendation in:  
       Field Wiring and Noise Considerations for Analog Signals
     http://zone.ni.com/devzone/cda/tut/p/id/3344

My question is:   if more than one grounded source is connected in NRSE configuration,
                         does this cause ground loops, since the input commons are all connected
                         to AI-Sense, no matter what the state of the multiplexer?

Thanks and Regards,
Mike Saginaw

[Erik_J]

Hi Mike,

Yes, if more than one grounded source is connected in a NRSE connection, you will get a grounding loop.  And yes, the input commons are all connected to AI-Sense, no matter what the state of the multiplexer.  Here is a link to a National Instruments webpage on grounding:
Ground Loops: Measuring Grounded Signal Sources

If you absolutely must use NRSE, I would suggest plugging in your measurement device and signal source into the same wall outlet to increase the chance that they will have the same ground.

I hope this helps!
- Erik

Message Edited by Erik J on 12-14-2006 09:51 AM