I am using LW/CVI 4.0 and am performing DAQ with an SCXI 2000 chassis
containing SCXI 1200, 1102, 1161, 1303. We are taking Thermocouple readings
each
second or so and send an output signal based upon these readings. The program
runs a timer loop while in operation. It works fine most of the time, but
every
so often the temperature readings, which usually measure between 200 and
500 F, will start to drop, they become negative and march quickly off towards
negative infinity, decreasing greatly each time through the loop. Other
times they
will march upwards, becoming large positive numbers quickly. However we
know the
actual temperature has not deviated from between 200 and 500 degrees.
I was
told perhaps there was a voltage building up and it was corrupting
one
channel and feeding back through a common ground, however the thermocouples
are
hooked up differentially, and so I don't think that is it. I have tried
introducing a small (1.5 V)
voltage to a channel and it only corrupts one channel, not all of them at
once like the current problem. Is it possible we have a setting wrong in
the 1102 signal conditioner? Or something else? Any help would be gratefully
appreciated.
Jeff Blackburn
