A thermostat is a component of a control system which senses the temperature of a system so that the temperature is maintained near a desired set point. The thermostat does this by switching heating or cooling devices on or off, or regulating the flow of a heat transfer fluid as needed, to maintain the correct temperature.
The most common of these technologies in thermostats is the bimetallic strip. This technology uses two thin strips of different metals — such as copper and iron, copper and steel and brass and steel — bonded together and rolled into a coil. As the temperature changes, the different metals expand or contact at different rates, causing the strip to bend. When the strip bends enough to touch an electrical contact and complete an electrical circuit, it turns on the heating or cooling system. If the temperature changes enough to unbend the strip, contact is lost, and the system turns off. Thermostats are applied in automotive air-conditioner, heat exchanger as well as in household appliances such as refrigerator, air-conditioner, water heater, electric cooker and electric kettle.
1. Terminal: Ag/BZn, Ag/Cu/Fe, AgNi(10)
2. Button contact: AgNi(10)/Cu/Fe430, AgCdO/Cu/Fe430