reading combined SCXI and daq board readings

[benegin]

I have a system that has a PCI-6251 data acquisition board A SCXI-1000 with 4 SCXI-1125 and 4 SCXI-1313. I am reading 32 channels of data It is being multiplexed onto channel 0 of the PCI-6251 daq board. I want to read another voltage on another channel of the PCI-6251 daq board. I am coming off the back of the SCXI-1000 chassis with a cable and going to a terminal module. I have all 33 channels configured as global channels in Measurement and Explorer. I am using the daqMX read vi.  Whenever I apply a voltage on channel one of the PCI-6251 board most of the SCXI channels will shift in voltage. Should this technique work?  I have done this using traditional daq with a different daq board and was able to get good results. The reason I am trying to get another channels is I need to read 33 inputs. Thanks for any suggestions.

[TheWoost]

Hi benegin,

That is odd behavior that you are seeing, and there should be no problem in setting this up as you have described.  You indicated that "most" of the SCXI channels shift in voltage.  Are they the same channels every time, and are the channels isolated to certain SCXI-1125 modules in the chassis?  What is the magnitude of the voltage offset that you see on the channels in question (is it the same offset on all of them)?  Please provide any additional information that may be of help.

Regards,
Andrew W
National Instruments