Academic Hardware Products (myDAQ, myRIO)

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Can NI myDAQ ai0 and ai1 be connected directly with thermocouples to measure temperature???

Hi,

 

I am trying to use myDAQ to realize both temperature measurement and digital output.

 

By reading this page I have learned that how I can create a task for temperature measurement using thermocouple with a certain NI device.

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

 

What I found to be really interesting is that when I create a task for myDAQ temperature measurement using a thermocouple when my NI myDAQ is connected with my PC, two AI ports ai0 and ai1 both appears in the create task window!!

 

I never found any information from NI myDAQ manual that "AI0 and AI1" can be connected directly with a thermocouple to measure temperature without using additional conditioning system. But this window suggests that myDAQ can be used in this way, is it?

 

 

I am still trying to do it this way, and I'll post some results here again.

 

I would be really appreciate if anyone could confirm or disprove my guess. Thank  you.

 

PS:

Attached is the 

 

 

 

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Attached is the screenshots for "create new task" in NI MAX

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Message 2 of 5
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I would guess the myDAQ uses comparable hardware to the USB-6008 and USB-6009.  If this is true, you might want to take a look at this:

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

 

You generally want to look at hardware that is geared towards this particular measurement.

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Thank you for your reply.

 

I actually have a 9213 to do thermocouple measurments. I just want to know, if thermocouples can be connected directly to NI myDAQ it will be pretty convinient for me to make prototypes.

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myDAQ spec sheet: http://sukjaro.eu/ELFT-NI-palyazat/myDAQ_Manual.pdf  Look at page 36.  You'll see the ADC is a 16-bit ADC.  You'll also see there are only two input ranges for AI on the myDAQ:  +/- 10V and +/- 2V.  This means the +/- 2V range would offer the highest resolution for you.

 

4V/(2^16) = or 61uV  That's larger than the voltage response of a thermocouple.  If you look at the absolute accuracy, you're looking at +/- 4.9mV for the +/- 2V range of the myDAQ.  4.9mV is 4900uV.  If the accuracy is only useful within 4900uV and you need a voltage response 56uV or less, you're using a tool that isn't well fit for the job.

 

Can they be connected directly?  Sure.  But, I definitely wouldn't suggest it.  4900 is 87.5 times 56.  That's a pretty big jump and could lead to some inaccurate readings.

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