R type thermocouples

[OConnoj8]

Hi I Hope this is the correct thread.


I am trying to calibrate an oven its very old and has an R type thermocouple the range is 450 to 600 deg C.

I am gettinjg a loan of a milliamp source and think i can get my hands on a millivolt source.

How do i proceed.

Thanks for any help in advance

 

[btrueblood]

The millivolt source will allow you to calibrate the electronics that the thermocouple attach to. You need a table of type "R" thermocouple emf vs. temperature, such as might be found in

http://srdata.nist.gov/its90/main/

But, that does not "calibrate an oven". The next link in the chain is the thermocouple itself. You can calibrate new thermocouples using the techniques described in

http://www.astm.org/Standards/E220.htm

But that doesn't help if you are re-using the existing thermocouple. Thermocouples can change in properties over time (see section 1.2 of the referenced standard). At the very least you should compare the oven thermocouple reading versus a seperate, calibrated temperature measurement. Suggest you visit

http://www.nanmac.com

and read up on some of their literature regarding thermocouples and calibrations, measurement accuracy, etc.

 

[arunmrao]

good advice from btrueblood. It is more tricky to calibrate R type thermocouples as the relationship between emf and temperature is nonlinear. Also remember to add cold junction compensation if you have not already considered that. Hope your emf source is quite accurate.

Learn the rules,so you know how to break them properly.
Dalai Lama

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