Hello;
At this point, the problem can be anywhere, at your thermocouple, at the terminal block, SCXI module, or even at the DAQ board.
I advise you to try narrowing down the possibilities, by hooking up a well behaved DC signal to your set up, and use Measurement and Automation Explorer Test Panel to do the readings.
Hope this helps.
Filipe A.
Applications Engineer
National Instruments