What is a temperature switch?

A temperature switch or thermal switch is used to open and close switch contacts. The switching status of the temperature switch changes depending on the input temperature. This function is used as protection against overheating or overcooling. Basically, the thermal switches are responsible for monitoring the temperature of machinery and equipment and are used for temperature limitation.

What types of temperature switches are there?

Generally, a distinction is made between mechanical and electronic switches. The mechanical temperature switches differ in the various switch models, such as bimetal temperature switches and gas-actuated temperature switches. When a high accuracy is required, an electronic temperature switch should be used. Here, the user can change the limit value themselves and set several switch points. Bimetal temperature switches, on the other hand, operate with low accuracy, but are very compact and inexpensive. Another switch model is the gas-actuated temperature switch, which is used especially in safety-critical applications.

What is the difference between a temperature switch and a temperature controller?

A temperature controller can, using a temperature probe, determine the actual temperature and then compare it with the set point. The desired set point is adjusted via an actuator. The temperature controller is thus responsible for the display, control and monitoring of temperatures. Temperature switches, on the other hand, trigger a switching operation depending on the temperature and are used to open and close circuits.

What is a bimetal temperature switch?

Bimetal temperature switches determine the temperature using a bimetal disc. These consist of two metals, which are used as strips or platelets and have different thermal coefficients. The metals are usually from zinc and steel or brass and steel. When, due to a rising ambient temperature, the nominal switching temperature is reached, the bimetal disc changes into its reverse position. After cooling back down to the reset switching temperature, the temperature switch returns to its previous state. For temperature switches with electrical latching, the power supply is interrupted before switching back. In order to achieve the maximum clearance from each other, the discs are concave-shaped when open. Due to the effect of heat, the bimetal deforms in the convex direction and the contact surfaces can securely touch each other. Bimetal temperature switches can additionally be used as overtemperature protection or as a thermal fuse.

How does a bimetal switch work?

Bimetallic switches consist of two strips of different metals. The bimetal strips are joined together inseparably. A strip consists of a fixed contact and another contact on the bimetal strip. By bending the strips, a snap-action switch is actuated, which enables the circuit to be opened and closed and a process is started or ended. In some cases, the bimetal temperature switches do not require snap-action switches, as the platelets are already curved accordingly and thus already have a snap action. Bimetal switches are used as thermostats in automatic circuit breakers, irons, coffee machines or fan heaters.