Thermo-temp’s own Keith Kieschnick discusses thermocouple types in this introduction to thermocouples video.
There are various types of thermocouples – Industrial Beaded, MGO, and for higher temps Noble Metals.
Depending on the atmosphere or environment of the process there are various protection tubes. Some types include; stainless or inconel, ceramic, or ceramic-lined stainless & Inconel. Selecting the correct combination will ensure that your process produces quality and reliability results.