TC-08 K type thermocoupple length.

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TC-08 K type thermocoupple length.

Post by proe » Tue Aug 16, 2011 11:46 am

I'm a new TC-08 data logger user. I would like to ask these guestions:
1) is there any way to use an extension cable for the K type thermocouples. Because, I need to measure, hot water temperature lost in different points in a closed industrial cleaning system. Therefore, cable length of the sensor should be at least 30 meter.
2) is it possible to repair a K type broken thermocouple?

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Re: TC-08 K type thermocoupple length.

Post by olepagh » Tue Aug 16, 2011 6:50 pm

Yes thermocouples can be extended, but you have to use a 'compensating' cable, i.e. typically multicore cable made from the same metal alloy as the thermocouple itself, but normally not so pure and therefore cheaper.
You also have to connect via "compensation" plugs and sockets, again made from the same material.

If you need 30 meters extension, you will probably have to check that the resistance of the extension cable does not exceeds the maximum resistance that the converter can operate with.
Also a shielded cable may be needed to reduce noise from other electronics and the main line.

If the thermocouple sensor is made of 'simple' K wire, it can just be cut and shorted anywhere to form a new thermo junction at the short.
May be it's a good idea to isolate the junction with epoxy if the temperature to be measured do not exceed 100 deg.C.
Normally a thermo junction is 'spot' welded, but it often works with just tighten the wires hard together or soldering them together.
If the broken thermocouple is inside a thin metal tube, it can usually not be repaired.

Here is an introduction to thermocouple and theory:
And some more:

The word "thermocouple" gives over 9 million hits on Google, so it's not hard to find theory and practical hints.
/ Best regards


Re: TC-08 K type thermocoupple length.

Post by proe » Wed Aug 17, 2011 8:17 am

Hi Ole,
Thanks for the answer.
I will instruct the extension cable according to your advices.
About reparing the K type wire thermocoupple, I did already twisting the wire together and solder them but
soldering is not really working well. Anyway, I did somehow and test the thermocoupple but it was falling and giving out strange data during the test. Maybe this time, I try epoxy or make a spot weld.
Best regards.

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