Hello hello,
I am using the scb-68 board and reading a set of thermo couples in labview 7.0. The program is set up so that the cold junction is set read on channle 0 and the other thermo couples are on 1 to 3. In labview the cold junction temperature is added to the other voltage readings from the other thermocouples. For the last year or 2 this has worked fine and all the the temperatures are accurate.
Yesterday I gounded one of the thermo couples that is located on pins 31 and 64. I am working in RSE mode so to add another device it uses the same negative terminals as the adjacent input device. The transducer called for a ground on its negative end. I have since removed this and put the device on a seperate channel away from everything else (it works fine).
However now in LV instead of compensating for the ambient temperature it just adds the two voltages together. Eg. ambient/cold junction is reading 25C, thermo couple is reading 26C, output temperature is now 51c instead of 26. I dont think this is a software problem either, as even my old programs are doing the same.
Something I think is amiss on the board so that the cold junction temperature is not being compensated for when the values are passed to Labview.
Has anyone else seen this problem? What is the fix for this problem? Fuse is fine, Cold junction is reading correctly and switches s1-5 are in the correct position.
Thanks,
-Whil
