6221 and grounding issues (eventually).

[Kentmey]

Hi,

I am using the attached vi (modified from sound and vibration toolkit), on the 6221 DAQ.

I am using the output channels and input channels as suggested.

I am using an RC circuit (1kohm, 1mF) in serie to test it.

Yet, I have quite a few issues in choosing the best mode (RSE, NRSE, differential, pseudodifferential...).

Currently, in RSE, I have an issue in AI1 : even when the wire is not connected, I am still recording a signal quite similar to AI0. I am actually reading it from any channel not connected. It is not noise because It has the same sine wave oscillations, and offset.

I assume this could be due to grounding issue, which I don't know much about. Any clue/suggestion on that matter?

Regards,

Kentmey

[ceties]

This might give you a few answers:

http://digital.ni.com/public.nsf/websearch/73CB0FB296814E2286256FFD00028DDF?OpenDocument

http://digital.ni.com/public.nsf/websearch/4E9B8B3F8FD3A31B862562B5004EA1D9?OpenDocument

http://digital.ni.com/public.nsf/websearch/B9BCDFD960C06B9186256A37007490CD?OpenDocument

http://zone.ni.com/devzone/cda/tut/p/id/4836 

[Ben]

try tconnecting the un-used channels to ground.

Cross-talk between channels is often the result of the residual charge on the input capacitance not being bed-off when switch channels in the sampling process. This alos occurs when the sources of signals have a very high output impeadence.

Ben

[Kentmey]

What unused channels ? all other AI (make 14 channels...)???

Could differential for both channels and putting - to ground make the trick?