How to configure CJC on USB-9211 in DAQ Assistant?

[Ed Henrie]

Note:  Reposted from LabView forum...

I have a new USB-9211 (cRIO-9211 with carrier) and am using LabView 7.1 to create a DAQ application.  When using the DAQ assistant I configure 4 K-type thermocople channels and set the options therein.  On the option for CJC Source, the options are: "Built in", "Constant", & "Channel".  In MAX it shows the CJC as a seperate channel, presumably a semiconductor type temperature device built into the 9211, but in DAQ Assistant it doesn't show this channel.  So, should I choose the "Built in" option for CJC compensation, or is there another way to apply the CJC compensation?

Thanks,

Ed

[Ryan_V[DE]]

Ed,

When using the test panels in MAX, one of your options is the _cjtemp. This channel will read the voltage of the built-in IC temperature sensor. When using the DAQ Assistant to specify thermocouple channels, the _cjtemp will not show up as the driver knows that you cannot plug a thermocouple into it. By selecting "Built-In" for CJC, this tells the driver to automatically read the value of _cjtemp and apply the appropriate conversion. You could read the _cjtemp as a voltage channel (but not in the DAQ Assistant) and apply CJC on your own, but what would be the fun in that?!? Let DAQmx do the work for you.

Hope this helps,

[JAMR]

Hi, what should the CJC voltage value read at around 22 deg. C?

I'm not sure if the temperature being output is offset do to a bad cjc sensor or device

needs to be calibrated or configuration. I created a task within Measurement and Automation Explorer

and the temperature is around 5 degrees C warmer, when selected Built in  under source

if constant and a value of 25 is used the temperature output makes more sense.

I used test panels and read the _cjtemp channel and it read 0.7

any suggestions?