Strain readings jump suddenly

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Hello,

I am using a NI9237 with the cRIO to read 2 full bridge type II strain gage configurations (channel 0 and 1). The system is now deployed for over a week and I went out to pull data from the cRIO. The readings looked as I would expect (0 - 50ue) until yesterday when a large spike of ~200microstrain was recorded by both channels and stayed there. However, channel 0 went up 200 and channel 1 went down 200. This happened instantly and simultaneously on the two channels and instead of fluxuating around 0 they now fluxuate around 200 and -200 respectively. I rebooted the system today and it went back to normal levels of strain. Has anyone ever experienced this problem?

Thanks,

Andrew

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After looking at the values, I suspect the channels are flipping signals. The plus or minus 200 ue was due to the offsets I had set. originally in an unstrained state channel 0 would read 114ue and channel 1 would read -93. These were taken out so that zero strain would be in the unstrained state. When the channels flip, channel 0 would read -93 minus 114 for -200ue, and channel 1 would now read 114 minus -93 or +200ue.

Therefore I'm confident the channels are flipping signals for some reason. I observed channel flipping while creating my program... when the VI was stopped using the abort button and then restarted the 9237 channels were flipped. Only when I used the "stop" button used to stop the program while loop did the channels not mix up.

I guess I'm not sure if this is a programming or hardware issue... any thoughts?

Thanks,

Andrew