How to select the temperature switch

A temperature switch is also called  Temperature controller, thermal relay. The Normal Open temperature switch is "on" at low temperature. When the temperature rises to the operating setpoint, the temperature switch turn off; when the temperature falls below the operating temperature, the temperature switch turn on again.

Bimetallic Temperature switch is a kind of temperature switch which uses bimetal as temperature sensing element. When the electrical appliance works normally, bimetal is in the free state and the contact is in the closed / open state. When the temperature rises to the action temperature value, the bimetal element will generate internal stress and act quickly when heated, open / close the contact, cut / close the circuit, thus playing the role of thermal protection. When the temperature drops to the reset temperature, the contact will automatically close / open and return to the normal working state. It is widely used in household electrical machinery and electrical equipment, such as washing machine motor, air conditioning fan motor, transformer, ballast, electric heater, etc.

Dual Metal Temperature Switch

This compact bimetallic temperature switch will could work with most i...

For different temperature measurement range, the user should choose different structure of temperature switch. In the temperature range of 0 ℃ ~ 100 ℃, the solid expansion type temperature switch is usually used. In the temperature range of 100 ℃ ~ 250 ℃, the gas expansion type temperature switch is mostly used. For the temperature range above 250 ℃, only thermocouple or thermal resistance thermometer can be used, which is converted by measurement transmitter, It is analog electric signal, and then the electric signal is converted into switch signal.

The working principle of solid expansion temperature switch is to use the difference of length change of different solid, after heating to produce displacement, so as to make the contact act and output the switch signal of temperature. For example, there is a temperature switch made of bimetallic sheet (brass sheet overlapped on indium steel sheet). Because the linear expansion coefficient of brass sheet is larger than that of indium steel sheet, the bimetallic sheet will bend when heated. When the specified temperature is reached, the free end of bimetal (the moving contact of temperature switch) will produce enough displacement, disconnect from the fixed static contact, and send the switch signal.

The gas expansion type temperature switch works according to the principle of gas pressure type thermometer. It has a temperature measuring package filled with nitrogen, which is connected to the measuring element of the pressure switch through a sealed capillary. When the measured temperature reaches the specified value, the inflation pressure in the temperature bag makes the pressure switch act.

Temperature Transmitter

GE-378 Temperature Transmitter is the high performance temperature tra...