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Old 02-17-2014, 04:14 AM   #1
farmskis
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Default Thermocouple question

I have one long thermocouple. Can I cut it into two shorter lengths and on one create an exposed junction by twisting and soldering and have two thermocouples? Anything special I would need to do? In theory it seems it should work. I believe it is a type t or k and I don't plan on using it above temps above the melting point of the solder.

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Old 02-17-2014, 04:27 AM   #2
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Yes you can.

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Old 02-17-2014, 12:06 PM   #3
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Doesnt the length of the wire on a thermocouple directly effect its readings / range?

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Old 02-17-2014, 12:13 PM   #4
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Quote:
Originally Posted by augiedoggy View Post
Doesnt the length of the wire on a thermocouple directly effect its readings / range?
That is my understanding.
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Old 02-17-2014, 12:47 PM   #5
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After reading a little more I believe the junction of the two different metals is the key in the thermocouple. I do not believe length (at least in the distances I am dealing with) will affect the reading. It looks like shortening is a fairly straight forward process... Lengthing might be a different story because it could potentially add junctions.

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Old 02-17-2014, 02:27 PM   #6
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My guess is that the junction of two metals is typically only at the very end and then it's spliced onto typical wire for the long run cable. If that's true, you can't chop up the wire and solder a bunch of junctions. I'd be happy to be told I'm wrong.

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Old 02-17-2014, 02:46 PM   #7
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Quote:
Originally Posted by augiedoggy View Post
Doesnt the length of the wire on a thermocouple directly effect its readings / range?
No, length does not matter - what matters is the junction between the two alloys. A K thermocouple has one wire made of Chromel alloy and the other made of Alumel alloy. Soldering the ends together will just hold the two wires tight together but the join & voltage will still be the same.
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Old 02-17-2014, 03:15 PM   #8
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No need to solder the ends together. Just twist them.

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Old 02-17-2014, 05:44 PM   #9
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Quote:
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No need to solder the ends together. Just twist them.
I agree but soldering will make sure they don't loosen up.

The lab I worked at when I was in school used to make their own thermocouples all the time. The tech who worked in the lab would pull some thermocouple wire off a spool then he would twist the ends together and dip the end into a solder pot. Most of the thermocouples were only a few feet long but he made some over 20 feet and they measured fine.

He said back then that the only thing you can't do is splice the wire in the middle. If you needed a longer one you had to start over.
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Old 02-18-2014, 10:11 PM   #10
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I have cut the length to two shorter pieces. Twisted the new ends together to form two seperate thermocouples. Both read accurately so it seems cutting had no effect on accuracy.

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