Refractory metal thermocouples are manufactured with wire that is made from the exotic metals tungstenand Rhenium.
These metals are expensive, difficult to manufacture and wire made with these metals arevery brittle. These thermocouples are intended to be used in vacuum furnaces at extremely hightemperatures and must never be used in the presence of oxygen at temperatures above 300ºC.
There are several differentcombinations of alloys that have been used in the past but only one generally used atthis time.
- Type C - The type C thermocouple is made with a tungsten/5% rhenium positive leg and tungsten 26% Rhenium negative leg and has a temperature range of 0 - 2320ºC (32 - 4208 ºF).
- Type G- Type G thermocouple technically also known as WM26Re. The type G thermocouple has alloycombination of tungsten (W) as positive lead and tungsten + 26% Rhenium (W-26% Re) as negative lead.Maximum useful temperature range of this thermocouple is 0 to 2320ºC.
- Type D- Type D thermocouple technically also known as W3ReM25Re. Type D thermocouple has alloycombination of tungsten + 3% rhenium (W-3%Re) as positive lead and tungsten + 25 % Rhenium (W-56% Re) as negative lead. Maximum useful temperature range of this thermocouple is 0 to 2320ºC.