thermocouple measurement directly into USB DAQ

[jon_mcbee]

The 6211 will be better than the 6008, the 6211 is 16 bit with voltage range of 400mV and the 6008 is 12 bit with voltage range of 2V.  The 6211 will have be able to measure changes of about 1.5 °C using the type of K type thermocouple.  I got this number by doing the following.  16 bit means that there will be 2^16 distinct values = 65536 distinct values.  There is a 0.4V range so => 0.4V / 65536 = 0.006mV is the minimum change in voltage the 6211 can measure.  We know that the K type thermocouple is 0.0041mV/°C so we see that 0.006mv / 0.0041mV/°C = ~1.5°C.  As long as you dont need to measure a change in temperature smaller than 1.5°C the 6211 should do the job for you.  Always remember that noise can cause issues.

Good Luck!

[StevenA]

jmcbee is correct, this would be  a much better device.  It still does not have a built in CJC (at least I didn't see it in the docs) so you will want to make another non-thermocouple temperature measurement for your CJC compensation.  See this link for more info about CJC.

[vijaya]

Hi,

Can Iread the thermocouple directly or do I need to implement any calibration to read the temperature.

Thanks,

Vijay

[SynME]

Just noting, I spend a couple hours trying to find a better solution, and realized this post was wrong:

   "We know that the K type thermocouple is 0.0041mV/°C so we see that 0.006mv / 0.0041mV/°C = ~1.5°C."

The Sebeck effect is .041 mV/°C, and change from 0 to 1°C goes from 0.000 mV to 0.039mV.

This results in a 0.006mV / 0.039 mV/°C = ~ 0.154°C increments, which should be acceptable for most applications.