Thermocouples are the temperature sensors that tell the controller the information it needs to run the program. In our Glass kilns we use 3 types of thermocouples depending on the model.
On our smaller 120 V kilns we use exposed Type K thermocouples and on our larger kilns we use a thermocouple that is protected by a metal sheath. Both are extremely accurate and should last a very long time when fired to only Glass fusing temperatures.
If you ever need to replace one (which is doubtful unless it gets banged with a shelf), the instructions are very easy to follow.