Thermocouple Operating temperature
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Thermocouple Operating temperature

by natec on Wed Jan 30, 2013 7:36 pm

Hello,

I recently purchased a 1m K type thermocouple and am waiting for the amplifier to become available. My question is that the thermocouple is listed as being good to 900F/500C ( I need to go to 800 regularly for short burst) but the heat shrink on the thermocouple is clearly marked 125C. Is this going to be an issue?
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Re: Thermocouple Operating temperature

by adafruit_support_bill on Thu Jan 31, 2013 5:55 am

The heat-shrink will burn off, but that will not affect thermocouple operation.
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Re: Thermocouple Operating temperature

by retrolefty on Sat Feb 02, 2013 11:43 am

Thermocouple insulation operating temperature is always an issue. If the insulation used 'melts off' then the two couple wires will short anywhere along their length where the insulation is gone, causing the measurement point to 'move' to the point where insulation is still functional and they may not be at the same temperature as the end of the TC.

There are two maximum temperature ratings for a typical thermocouple, one is the basic limit of the metal wires used which is fixed in value as defined by being a type J or K or R, etc. The second limit which is lower is the insulation used to separate the two wires from each other except at the very end where they are shorted together that being the 'measurement point'. One can buy couples with special mineral insulation or physical separating the wires with ceramic beads with two holes to keep the wires separated. But yes if the insulation is exposed to temperature higher then their rating then if will effect the reading.

Omega Engineering is a very good source of technical information for TC and other temperature sensors

http://www.omega.com/thermocouples.html
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Re: Thermocouple Operating temperature

by adafruit_support_bill on Sat Feb 02, 2013 11:51 am

If the insulation used 'melts off'

It is not the insulation that is melting off in this case. The wires are individually insulated and the pair is encased in a fiberglass sheath.
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Re: Thermocouple Operating temperature

by retrolefty on Sun Feb 03, 2013 1:35 am

adafruit_support wrote:
If the insulation used 'melts off'

It is not the insulation that is melting off in this case. The wires are individually insulated and the pair is encased in a fiberglass sheath.


Ah, and rated for?
( I need to go to 800 regularly for short burst)
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Re: Thermocouple Operating temperature

by adafruit_support_bill on Sun Feb 03, 2013 6:49 am

900F/500C The OP knows this. His question was about the heat-shrink.
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