Measurement of high temperatures, higher than 1000 C, using ceramic based thermocouples is a well known process. To do this successfully the resistance wires throughout the thermocouple must be insulated and protected.
Using Ceramic materials to guard the platinum based wire is a method that has been used for many years, due to exceptional heat resistant properties of the materials. The thermocouple sensors is considered the most widely used heat measurement implement which is utilized for measuring the temperature inside of a furnace, typically used for your melting or heat therapy for metal or indeed for manufacturing ceramic products.
The ceramic components in the typical thermocouple device will be the outer protection tube which is in contact with the furnace. Sometimes multiple tubes are being used inside each other to deliver the level of insulation and protection required.
Ceramic insulators (Tubes with 2 or higher core holes through them) may also be used to isolate the 2 or more wires that proceed to the bi-metallic joint on the head the point from where sens0rs temperature is measured.
The typical materials for your tube is really a 99.7% alumina material, impervious tube, that is attached typically to some metal thermacouple head, containing a terminal block which is used in order to connect to some standard wire towards the instrumentation. In a less demanding heat atmosphere a mullite tube can be utilized like a cheaper alternative, that can work sufficiently as much as 1600 ‘oc. The mullite tube is likewise an impervious tube and possesses 60% alumina content.