What is a bimetal sensor?

What is a bimetal sensor?

A bimetal sensor is a device that is made up of two metal sheets, each one of a different material with different characteristics. These sheets monitor changes in temperature and depending on the heat that passes through them, they can contract or expand.


How does a bimetal work?

The operation is quite simple, two metal sheets are placed, usually one is bronze and the other is steel. When these are subjected to a heat source, the bronze sheet tends to expand and the steel sheet contracts, causing a curvature to form that depends directly on the degree of temperature to which they are exposed.

Bimetal function

Where are these sensors used?

These sensors can be used for temperature applications, for protection against overcurrents or in some other more specific applications.



For temperature applications we can find two different ones as thermostats or as thermometers.


We can find two different types: fixed and variable temperature, these sensors are placed together with a heat source and are used to regulate the temperature in the selected degrees through a mechanism.

For example, for those of variable temperature we have a heating system and we select 22º, this appliance generates the necessary heat until reaching the selected limit and when it exceeds that limit, the circuit is interrupted, once the temperature is below the level it returns to activate and so on to maintain the selected temperature.

Bimetal thermostat


The sheets are placed next to a mechanism that translates the curvature on a temperature scale either in degrees Celsius, Kelvin or Fahrenheit.

Bimetallic thermometer

Over current

Bimetals are mainly used to monitor the amount of electrical current that passes through a conductor, when it exceeds the nominal values ​​it generates a heat source that makes the sheets react and they form a curvature that causes the circuit to be interrupted, indicating that there is an overcurrent at that point.

Bimetal relay

Specific applications

Bimetallic was previously used in the flashing lights of automobiles, even though these have already been replaced by electronic components.