I have an SCXI-1000 chassis with an 1102C module and 1303 terminal block. This chassis also has an 1127 mux module with 1331 terminal block. I'm controlling the chassis with an SCXI-1349 plugged in to the 1102C module and a USB6361. I'm trying to read 2x K type thermocouples and 2x T type thermocouples in the 1303. The TCs are wired directly in to the 1303 with colors correctly oriented.
The problem I'm having is that I can start my VI and everything will read fine, the 4x TCs being about 25C ambient as expected. If I unplug them (male/female connector just outside the terminal block), only one or two will read an open TC voltage (an equivalent temperature of -124C or something like that) while the others will continue to read about 25C despite the fact that they're no longer connected. If I leave the TCs unplugged, stop the program, restart the chassis, and start the program again, they will all read the correct open TC temperature. This is a problem, since I need to be able to detect if the TCs are open (unplugged). Also, sometimes the TCs don't respond correctly to being heated up and will continue to read 25C even when placed in a 50C environment. Jiggling the connectors can sometimes fix this but only temporarily. I've verified that there's nothing wrong my connectors so I'm not sure why moving them can change the results.
I'm not sure what's going on, since this module/terminal block can read conventional voltages (on the order of ~0.7V) just fine with no issues whatsoever. I've tried a different 1102C module with the same results. I'm fairly confident that my VI is fine & I've attached the TC read portion. Is it possible that I just need to place a resistor between the TC- side and GND in the 1303? The wiring is hard to get to so I wanted to see if it was an easier fix before attempting this.
