CJC--where is it happening?

[chimchim]

Hi. I'm using a TBX-1328 terminal and scxi 1120. I have noticed when the room temperature increases, my data temps are going down.

So what I'm wondering is if the CJC is done in the hardware and is transparent to the DAQ software (I'm using vb.net), or if I need to write an application in vb.net to look at the thermistor channel and compensate the other channels accordingly. Thanks.

[JoeSavage]

This depends on what driver software & features you are using. With DAQmx, you when you create a thermocouple channel, you specify the CJC source (which you would set to built-in in your case). Or if you are using traditional DAQ and you create a thermocouple virtual channel, you also can specify the CJC source to built-in. In both of these ways, the software handles the CJC automatically. If you read your TCs any other way (such as by reading voltages and doing the scaling yourself) you'll need to do the cold-junction compensation yourself.

Joe

[Stocklone]

I am running in parallel mode so I don't have access to the built-in CJC.  So now what do I do?

[Ed W]

Hi,

Thank you for posting to the NI forums.  There is a Knowledge Base article that address this issue.  Are you using the same device configuration as the previous posts – if not, which devices are you using? 

How Can I Address and Use Cold Junction Compensation (CJC)

I hope this helps.  Post back if you have further questions.

Ed W.

Applications Engineer

National Instruments