How to measure air temperature with USB 6351

[ncm]

I am trying to measure air temperature with my USB 6351.  I have a T thermocouple attached to AI.6 (red wire to pin 24 and the blue wire to pin 23).  When I use the MAX I am getting a reading between 16 and 19 for a few seconds and then it drops quickly.  I have attached the screen shot of the MAX that I am using.  I am not sure if I have this set up incorrectly or where I am going wrong...  (I expect my temperature to be in the low 20's because similar setups in the building are recorded to being on average 22C)

[chris88 · Accepted solution]

Hi ncm

The USB 6351 does not have built in cold junction compensation, this means that you’ll need to set a constant CJC Value, which you are doing, but you need to measure the proper value your thermocouple.

CJC Value is the temperature of the cold junction of the thermocouple; when CJC Source is set to constant, the temperature value uses the same units as Input Range, in your case deg C.

You have to realize that the USB 6351 isn’t the best hardware to measure temperature.

Here are some articles that can help you:

http://digital.ni.com/public.nsf/allkb/E332E1D829059FB5862570AE005066B3

http://digital.ni.com/public.nsf/allkb/9B99C4C98952F38486256298005A236D

http://www.ni.com/white-paper/14338/en#toc2

[ncm]

Thank you, I was hoping that I could just use the 6351 so simplify my design but I can use my USB-TC for the conditioning (I was trying to downsize the test set-up while upgrading, I am having to use USB instead of the current PCI which is going to take up more table space)  I appreciate the help!