How Temperature Sensors Work

Sensors designed on the principle of metal expansion
Metals undergo a corresponding extension when the ambient temperature changes, so the sensor can signal this response in different ways.
Bimetal Sensor
A bimetal sheet is composed of two pieces of metal with different expansion coefficients attached together. As the temperature changes, material A expands more than the other metal, causing the metal sheet to bend. The curvature of the bend can be converted into an output signal.
Bimetal Rod and Tube Sensors
As the temperature increases, the length of the metal tube (material A) increases, while the length of the non-expanding steel rod (metal B) does not increase, so that the linear expansion of the metal tube can be transmitted due to the change of position. In turn, this linear expansion can be translated into an output signal.
Deformation Curve Design Sensors for Liquids and Gases
When the temperature changes, liquids and gases will also produce corresponding changes in volume.
Various types of structures can convert this change in expansion into a change in position, thus producing a position change output (potentiometer, sense bias, baffle, etc.).