Thermocouple junction introducing measurement error

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Southern Girl
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Joined: Wed Aug 15, 2007 12:35 pm
Location: North Carolina

Thermocouple junction introducing measurement error

Post by Southern Girl » Wed Aug 15, 2007 1:47 pm

I found this information and forum from a Googel search and man am I glad!

"Many measurement errors are caused by unintentional thermocouple junctions. Remember that any junction of two different metals will cause a junction. If you need to increase the length of the leads from your thermocouple, you must use the correct type of thermocouple extension wire (eg type K for type K thermocouples). Using any other type of wire will introduce a thermocouple junction. Any connectors used must be made of the correct thermocouple material and correct polarity must be observed."

The reason for my search was the result of a recent visit by a co-worker to a test lab (which will remain un-named) and he took this photo of their connectors for thermocouples. The connectors resemble those used for stereo speaker wire! (I tried to attach the photo, but it was too big) Not knowing exactly the type of material that is used for the connectors, how do you calculate the measurement error introduced by this setup or is there really some type of TC connectors made like that?

I would appreciate any information anyone has on this matter.

Thanks bunches!

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Post by PeterF » Thu Aug 16, 2007 2:43 pm

Yes, you are absolutely right! There is no way to compensate for random junctions like that. The correct metals must be used or as soon as there is a temperature differential between the junctions, error voltages are generated.

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