If we are working with high temperatures, or require very fast responses, we use thermocouples, which are still the union of two threads, therefore, the best response speed.
There are different types of thermocouples according to regulations and work range.
The most usual, the thermocouple K, J, T, B and S
for high temperatures.
In thermal treatments, thermocouples are usually used with special protection covers (sialon, pyrocermet, ceramic K710, K610, silicon carbide, etc.)