measuring temperature Via Thermocouple and USB-6009?

[bilbeigg]

Hi,

I am trying to perform temperature measurements using a k type thermocouple and the USB-6009 DAQ. I tried to use the Cont Acq Thermocouple Sample.vi from LabVIEW's example list, but unfortunately I don't know how to fit my DAQ and thermocouple in the vi code. I don't know how to create a thermocouple temperature measurement channel or how to get all the channels in the task, etc.

Any help is appreciated.

Thanks.

[jon_mcbee]

You should be able to use DaqMx to configure a task that will do this.  It should be pretty straight forward.

[bilbeigg]

I used daqmx to configure. I have my thermocouple attached to the right port, but the readings seem a bit off. the temperature goes from 0 to 100 C in like 2 seconds. Do you think my thermocouple is broken? Also, I dont know what to put for "error in".

I'm attaching a picture of my front pannel to show you the graph ...

Thanks again

[Joseph_Loo]

It sounds like you have a noisy input. Remember thermocouple values are in the 10s of milli volt range.

[CMal]

bilbeigg,

It should be noted that the USB-6009 is not well suited for thermocouple measurements.  It has 14 bits of precision with a minimum input range of +/-1V, which means it can only detect a voltage change as small as about 122 microvolts.  This is much too large a change to get a good temperature reading with most types of thermocouples.  Here is a discussion thread on the same topic (Note that the USB-6008 and 6009 are very similar):

http://forums.ni.com/ni/board/message?board.id=170&message.id=294080#M294080

Here is a knowledgebase that explains what you are seeing:

http://digital.ni.com/public.nsf/allkb/8166630BD6965EEA86256FDD0052E89C?OpenDocument

Chris M

Message Edited by CMal on 03-12-2008 12:17 PM