Problem with Non Reference Single ended and Differential measurements

[Geneva L.]

The following was misposted at the Real-Time DAQ category and should appear in this Multifunction DAQ category:

I am doing a differential measurement and then a non referenced single ended AI measurement using the same PCI 6025E card. Most of the time I get good measurements however a small percentage of the time I get very strange measurements.

[Geneva L.]

Make sure that you have set up each of your channels for the appropriate mode of measurement. By default, Measurement & Automation Explorer (MAX) has a property set for your card, either differential, nonreferenced singled ended, or referenced single ended. If all your channels are in one mode, then you can just left those defaults stay. Otherwise, as in your case, you would need to programmatically set each channel for the right mode.

For instance, in LabVIEW, the AI Configure.vi has an input parameter for "coupling and input config". This is an array of data that includes the measurement mode. Each element of the array corresponds to the element in the channels array, so you can configure each channel appropriately. Make sure that you have this set up in yo
ur program, and you should get the correct measurements.

Finally, double-check your physical connections to see that they match the measurement mode you chose. You can find this in the 6023E/6024E/6025E User Manual or the PCI E Series User Manual at the http://www.ni.com/manuals website.

Regards,

Geneva L.
Applications Engineer
National Instruments
http://www.ni.com/ask