In glass smelters, flue gas applications and in the brick and ceramics industries temperatures up to 1700°C (3092°F) can occur. This requires special thermometers with ceramic thermowells and thermocouples made from special metals, such as platinum and rhodium.
The ceramic thermowell external and sandwich coatings act as diffusion barriers. They serve as protection of the measurement point from mechanical and chemical damages in the process, e.g. from abrasive gases. The ceramic thermowell inner sheath is the ceramic capillary. It has the purpose of feeding and insulating the thermo wires. A higher number of ceramic protection coatings increases the life time of the measurement point.
Important influences are:
