For anyone who's paying attention, i am having problems with the TBX-1303 CJC sensor. i'm running LV 7.1 on a Windows 2000 machine. my card is a PCI-6052E connected to an SCXI-1000 chassis with an SCXI-1102 module and a TBX-1303 front end. using MAX i can read the CJC and get ~26 deg C. when i use a built-in LV example ("Acq CJC Temperature.vi" using DaqMX) to read the CJC, i get ~28 deg C. i started down this search because during a checkout of a data acquisition vi that i built, i discovered that while using a "calibrated" thermocouple simulator to verify my readings my vi always indicated a temperature that was ~2 deg C higher than what the simulator was set to. to get the correct measurement in the short time i had, i used an LM35CZ temperature sensor on an unused channel as my CJC. this device reliably puts out 10mV per deg C. this solution works but shouldn't be necessary. My scan times are as follows: i'm scanning 12 channels at once per second, that works out to be 1S/0.083 seconds
i've tried another TBX-1303 and get the same results. i started to think that the problem was with the DAQMX functions but then I borrowed and SCXI-1303 terminal block as a front end. to my surprise the readings were now correct!
does anyone have any information on this phenomena or suggestions for further trouble-shooting to find the cause of the error?
joe
