Bimetallic thermometer casing need to join in medium?

Bimetallic thermometer is made up of two layers of strong linear expansion coefficient difference is relatively large pieces of metal welded together, one end of the element as the fixed end, on the other side of the free end. When the temperature changes, because the bimetallic strip of material is different, linear expansion coefficient of relatively large differences, and produce different expansion and contraction, leading to the curving deformation of bimetallic strip, equipped with actuator (at the free end Dial pointer and temperature) So that it can directly show the temperature value. In the process of use, and sometimes we will match on a root bimetallic thermometer casing, then the bimetallic thermometer casing need to join in medium? We can know that, according to the principle of the bimetallic thermometer is through the heat element after thermal displacement to drive the pointer indicating temperature, so the bimetallic thermometer casing is not need to join any medium. With double metal thermometer casing mainly consider two aspects factors. It is easy to install and remove; But when using the environment pressure is greater than 40 kg, can protect the heat pipe.