Cross talk 6531 normal?

[ToeCutter]

If I acquire a signal on a single channel using this card and leave all the other channels disconnected, they pick up a signal of similar magnitude to the connected channel. Is this expected behaviour for this card?

[John_P1 · Accepted solution]

Assuming you mean the 6351, yes.  NI documentation refers to this behavior as ghosting.  

In summary, the capacitance at the input of the ADC is charged up to whatever voltage you have wired in on your first channel.  When the MUX switches to the next channel, the charge has nowhere to go (the channel is open and the input impedance is >10 GOhms) so the card will measure approximately the same voltage on the new channel.

Best Regards,

[ToeCutter]

John,

Yes I do mean 6351. I appreciate the detailed reply; case of RTFM I guess!

Cheers

Lee