Sheath material ranges from mild and stainless steel to refractory oxides (Ceramics) and a variety of exotic material including rare metals.
Sensor inserts are fabricated unit which is comprised by a sensor and a terminal base; the sensor is housed in a stainless steel insert tube, usually of 6 or 8mm diameter and, then it is inserted into the actual protection tube.
Good sheathing with physical contact between the insert tip and sheath end is essential to ensure good heat transfer. Spring contact is used in the terminal base to maintain this contact.
This arrangement facilitates easy replacement of the sensor whenever required.
In general, there are two types of protection tubes:
- Metallic protection tubes
- Non-metallic protection tubes