I'm making long term temperature measurements using a PCI6040E, SCXI1001, SCXI1102 32-channel thermocouple amp and a SCXI1303 isothermal block. These are making readings using J type t'couples. My customer's problem is that the measurements will be fine for a period of time (minutes, several hours) and then suddenly some channels will start giving really bogus temperatures, i.e.: -270 DegC vs the more realistic 35 DegC. I came in the last time it was doing this and when I went down into the code to my DAQ portion the DAQmx Read vi, set as analog, temperature, J type measurement was returning those numbers for the offending channels. Some were still giving valid numbers while others were giving the weird numbers and when a Fluke meter was used to measure the output of the "bad T'couple" it too was giving valid numbers. When I stop the LabVIEW program and go into DAQmx to try and troubleshoot it, there usually seems to be no problem. If I restart the LabVIEW program there also seems to be no problem, but when there is those numbers are coming out of the lowest level of code that I have programmed (the standard DAQmx read). I'm suspecting something "electromechanical" like connectors in/on the SCXI chassis, but the fact that it goes away when software is restarted is confusing me, as well as making troubleshooting difficult.
Thanks,
Putnam Monroe
PutnamCertified LabVIEW Developer
Senior Test Engineer North Shore Technology, Inc.
Currently using LV 2012-LabVIEW 2018, RT8.5
LabVIEW Champion