SCXI is only accurate for the first 5 minutes it is on

[Batsch]

We are trying to log a simple voltage and current with an SCXI 1001 and voltage card 1125. The data is good for 5 minutes and then sometimes it doubles the value or cuts it in half. The problems is somewhere in the SCXI (we think) due to monitoring a channel and watching it go out of whack. Any suggestions?

[RIO-Todd]

Greetings,

It sounds as if you are running into a grounding issue. Are your signals grounded or floating?

In cases where both signal lines at the transducer end are floating, you'll want to establish an earth connection at the SCXI-1125 by connecting the negative input line to chassis ground in the terminal block. You can directly connect the negative terminal (CH-) to the chassis ground or connect thru a bias resistor. This eliminates noise that may be riding on the floating signal and provides a path to ground for the floating signal.

This information can be found in the SCXI-1125 User Manual on page 2-2. I've linked the manual below.

SCXI-1125
http://digital.ni.com/manuals.nsf/webAdvsearch/85C7726245BE7391862567BE0056BAFD?OpenDocument&vid=niwc&node=13
2100_US

I hope this helps. Have a great day.

Regards,

Todd D.
NI Applications Engineer