Thermocouples reading errors with SCXI and LabVIEW 7.1

[fronk66]

Hello everyone,

This may be a terribly simple answer but I am a newbie so please put up with me. I am currently using a SCXI 1102 module with SCXI 1303 thermocouple terminal block for the signal conditioning end of things. I have a M series NI PCI-6280 DAQ card and am running LabVIEW 7.1 in Windows XP. Being a newbie, I have been using the DAQ assistant to set up my channels in a simple VI. I have setup channels for all my thermcouples (T type Omega brand). However when I display the data on my front panel, the temperatures are much higher than they should be reading (about 10-15 degree C). The thermocouples work fine I have tested them in other systems. It should be noted that the temperature also drifts up as the NI unit and Cold junction sensor heat up.

Any ideas for trouble shooting this? Is it possible to get the cold junction temperature from the 1303 terminal block through the 1102 module to verifiy that it is operating correctly. I have tried the same thermocouples with two different terminal block / module combinations so I don't think it is a hardware issue. Is there something really simple I am missing in the software?

Thanks for any help!

[devchander]

For starters, this "Acq CJC Temperature.vi" will help you get the temperture that is read by the cjc sensor.

Also, run the temp acq VI attached and see if you still have the kind of drift you have posted about.

Note: In the attached "Cont Acq Thermistor Samples-Int Clk.vi" select cjc source as 'internal', and do not specify any cjc channel.Read it documentation File>> VI properties>> documentation before executing the VI

Hope this helps

Regards

Dev