BNC-2120 cannot use built-in CJC in MAX for thermocouple measurements

[WaltF]

i have a PCI-6110 connected to BNC-2120 accesory. i am trying to use the thermocouple input on AI1 with a K-type thermocouple. i switched AIO to "temp reference" and AI1 to "thermocouple input". under my PCI-6110 device settings, i have BNC-2120 selected under accessories and the "CJC jumper set" box checked.

when i create a temperature virtual channel, i choose "built-in" as my CJC option, but when i run the test panel i get

"error -10010"

however, if i set up a separate virtual channel for CJC on AI0 and then choose "user select" as my CJC option and this CJC virtual channel, the test panel works. the CJC channel displays the correct room temperature, but my thermocouple reads ~3-4 degrees C too high.

i have two questions:

1. does anybody know why my "built in" CJC option does not work? do i have it configured wrong?

2. if i need to make a CJC virtual channel to use the built-in "temp ref", why is my thermocouple reading off by 3-4 degrees?

thanks in advance for any help. i just need to make a simple T measurement (with what i thought would be a simple setup), but i can't seem to get it working in MAX...

[e-Cash-Money]

Hello WaltF,

I am not sure why you receive an error when using "built-in" as your CJC option. It simply might be that the driver doesn't support that kind of configuration for the particular pieces of hardware you are using.

I did find a KnowledgeBase article linked below that gives a step-by-step process for setting up the CJC when using the BNC 2120. It sounds like it might be a scaling issue, but go ahead and take a look at it, hopefully it will help.

Take care,
E.Lee

http://digital.ni.com/public.nsf/websearch/E45ADD30F609AEC4862569CF00588DC9?OpenDocument

[JoeSavage]

Hi Walt, I just tried the same thing with a PCI-MIO-16E-1 device and NI-DAQ 7.4 and had no troubles, so this problem may be specific to the PCI-6110 driver. I don't have that type of device around, so I can't try it myself.

I recommend trying this with NI-DAQmx instead of traditional DAQ. NI-DAQmx 7.4 has a new channel calibration feature that allows you to compensate for any offset present in your measurement.

Good luck,
Joe