N9229 measurement error

[bill jackson]

We are using the Ni 9229 to measure a 13V, 30msec pulse and the measurement jumped to 4V came back down to 1.5V and rose exponentially to 7V any ideas on how to troubleshoot this? thanks Bill

[snowpunter]

Floating or grounded signal source?

Take a look at the attachment, the 9229 is differential so if you're using a floating signal source you should add a bias resistor.

[bill jackson]

Thanks for the connection diagram thats very informative! Why are the chassis ground symbols different for the source vs the Diff Amp? 

I'll go check for sure but the signal source is grounded to chassis but at a different location.

[WillPwr]

Hello, Bill!

In response to you most recent question, the second symbol is earth ground as opposed to chassis ground. The main point is that the source is grounded in such a way that will not introduce ground loops, but is stable enough to not cause the behavior you saw earlier. Please let us know if you're still seeing issues after following the diagrams posted by snowpunter.

Thanks!