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Thermocouple fabrication

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Hello,

I need to fabricate a thermocouple of K type. I need to have the thermocouple in metal sheathing of such material which can have good life at 1000°C in fluoride environment (molten cryolite). There has to be insulation between wires and metallic sheath. The final outer diameter of the assembly do not have to exceed 2.5mm.

Can somebody help me in this regard.

Maneesh C. Srivastava
- Nagpur, India

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Best method is to go to a commercial thermocouple fabricator. Mineral-insulated (magnesium oxide) type K thermocouple stock is readily available in a wide range of gauges and sheath materials, but welding of the hot junction and repacking the insulation around the hot junction and closing the end of the sheath by welding, are aspects of thermocouple production best left to those with the equipment and experience to do it properly.

Bill Reynolds [deceased]
consultant metallurgist - Ballarat, Victoria, Australia
We sadly relate the news that Bill passed away on Jan. 29, 2010.

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In addition to what Bill says, you need proper equipment to calibrate thermocouples to correlate output voltage vs. temperature. Welding wires of appropriate composition is the easiest thing. For insulation, you may string tiny alumina tubes over lead wires.

Mandar Sunthankar
- Fort Collins, Colorado