using pci4351 for built in CJC

[Researcher Institute of Technology SA]

How can i measure temp. using pci4351 using the built in option for CJC.Im using the example for pci435xx, but when i select built-in CJC, the readings are NaN.  I tried to select Ch0 as in ohms in measurement mode, but still no reading. Im using type K-thermo.  Is there a fixed CJC for this type of thermocouple.If i use 25 deg, the readings are not actuarate.Help me.

MS

[Neal M]

Hello MS,

The first thing to do is make sure that the CJC is functioning.  Depending on your setup (specifically your terminal block), this knowledgebase should help you determine if your CJC is working correctly.  If you are using LabVIEW 6.1 to program, take a look at this knowledgebase which outlines a similar issue.  This should not be the problem if you are in a later version of LabVIEW.

The task calculates what the cold junction voltage is by what type of thermocouple you specify you are using and the temperature of the junction. By setting the CJC value to constant,  what you are telling the task to do is to use a constant temperature to calculate the CJC value instead of using the internal temperature sensor.  So, if your room temperature is actually 23 deg and you set your CJC constant to 25 deg, your reading will be off.

If this information does not resolve the behaivior you are seeing, I am going to need more information about your setup.  Specifically, what example you are using, what language you are programming in, and what terminal block you are using. I am also not sure what you mean when you say "I tried to select Ch0 as in ohms in measurement mode".  Do you mean you are using a test panel in resistance mode?