Refractory Metal Thermocouples are manufactured with wire that is made from the exotic metals tungsten and Rhenium. These metals are expensive, difficult to manufacture and wires made with these metals are very brittle.
These thermocouples are intended to be used in vacuum furnaces at extremely high temperatures and must never be used in the presence of oxygen at temperatures above 300°C. There are several different combinations of alloys that have been used in the past but only one generally used at this time.
Type C- The type C thermocouple is made with a tungsten/5% rhenium positive leg and tungsten 26