Two categories of thermocouples are base metal and noble metal. Base metal thermocouples are types E, J, K, T, and N and use inexpensive metals such as nickel, copper, and iron. Noble metal thermocouples B, R, and S are platinum-based, tolerate higher temperatures, and provide greater accuracy than base metal thermocouples.
A typical application for noble metal thermocouples would include jet engines, rocket engines, turbines, exhaust gas sensing, glass manufacturing, heat treating, laboratory research, nuclear environments, power stations, and vacuum furnaces.
Noble metal thermocouples have widespread applications involving high temperatures in oxidizing or inert environments but require a ceramic protective tube. These sensors are often brittle, and their use in reducing atmospheres or metallic vapor-containing environments is inadvisable.
Insulators and protective tubes come in a variety of materials and forms. Typically, Alumina and Mullite. Mullite has excellent thermal shock immunity but low mechanical shock resistance. Alumina has good thermal and mechanical shock resistance and is resistant to gases up to 3,200°F.
In the harshest and most demanding conditions, noble metal thermocouples selection criteria include the temperature operating range, ambient atmospheric or media, the size and form, precision, and response time. For more information, or for assistance selecting the right noble metal thermocouple, contact:
