Measurement of high temperatures, higher than 1000 C, using ceramic based thermocouples is a well established process. To carry out this successfully the resistance wires throughout the thermocouple have to be insulated and protected.
The usage of Ceramic materials to safeguard the platinum based wire is a method which has been used for many years, because of the exceptional heat resistant properties of the materials. The temperature sensor thermocouple is regarded as the widely used heat measurement implement and is also used for measuring the temperature within a furnace, typically being used for the melting or heat treatments for metal or indeed for manufacturing ceramic products.
The ceramic components within a typical thermocouple device will be the outer protection tube that is open to the furnace. Occasionally multiple tubes are employed inside one another to deliver the level of insulation and protection required.
Ceramic insulators (Tubes with 2 or more core holes through them) are also used to isolate the two or more wires that check out the bi-metallic joint on the head which is the point from which sens0rs temperature is measured.
The common materials for the tube is a 99.7% alumina material, impervious tube, which is attached typically to a metal thermacouple head, containing a terminal block which is often used to get in touch to some standard wire on the instrumentation. In a less demanding heat atmosphere a mullite tube can be utilized as a cheaper alternative, which can work sufficiently up to 1600 ‘oc. The mullite tube is likewise an impervious tube and possesses 60% alumina content.