The thermocouple types can be categorized into two groups i.e. Base metal and Rate or Noble metal.
Type K, J, E, N and T fall into the Base metal category whereas Type R, S and B come into the Noble metal category.
In general, there are four classes of thermocouples which are mentioned below:
Home body class which is also referred to as Base metal Type. The temperature range for these types of thermocouples varies from -200°C to 1200°C.
Upper crust class, also known as Rare metal or Precious metal or Noble metal Type. The temperature range for these types of thermocouples varies from 0°C to 1600°C.
Rarified class, also known as Refractory metal Type
Exotic class which consists of various tungsten alloy thermocouples and many other standard and developmental devices. It is typically designated by Type W.
Each thermocouple type or calibration has a specific range of temperature and environment. However, the maximum temperature possible depends upon the thermocouple wire diameter.
The most preferred types of thermocouples are found to be K and N types since they perform well at high temperatures, whereas another industry preferred thermocouple is T type as it offers high sensitivity, low cost and simple operation.