Thermocoupling question

[earlburnermann]

I use a fieldpiece LT17A meter and have calibrated the ATB1 thermocouple that came with it. I also have a ATWB1 thermocoupling for finding wet bulb temperature and a ATC1 clamp for checking the liquid and suction line. My question is can I add or subtract the difference in temperature when using the clamp and wetbulb thermocouplers? There is about a four degree difference between the thermocoupling I calibrated and the other two.

[Rcb2875]

Are you saying that in ice water some of the clamps are showing different temps? Note that the ATC1 take about 20/30 seconds to stabalize due to the clamp plate.

[earlburnermann]

I find that all the thermocouplers have a slightly different reading. I calibrated the ATB1 thermocouple in pure ice water. Set it to 32 degrees and then switched to the ATC1 clamp thermocoupler. Found a 3 of 4 degree difference. The same with the ATWB1 thermocoupling. They don't match the ATB1 that was calibrated when they are tested in the ice water. Just off by a few degrees. I was wondering if the ATB1 measures 90 degrees and one of the others comes up with a temperature a few degrees higher or lower in the same location, can I just add or subtract the difference. Let's say I want to check the liquid line temp. My ATB1, which was calibrated to the meter reads 85 degrees while the ATC1 reads 87 degrees in the same exact location. Could I just subtract 2 degrees when using the ATC1 on the liquid or suction line to get the right temp?

[Rcb2875]

Sure. Just note what the temp difference is in comparrison to the control temp and add or subtract to make it right per thermocouple when measuring unknowns. Not sure why you are getting so many results though.

[knave]

When you calibrate a k-type thermocouple, it is specific to that thermocouple.

like RCB said,

calibrate the one you use the most and just subtract the difference on the others.

[earlburnermann]

Thanks for the help guys!