A cooker thermostat is a heat-controlled switch that is built into conventional ovens and other types of cooking units that rely on natural gas or electricity for power. The purpose of a cooker thermostat is to turn the oven on or off when a preset temperature has been reached. Other types of cooking devices that use such thermostats include toaster ovens, electric griddles, grilling machines, gas fired outdoor barbecues and more.
The primary method for designing the on/off switching mechanism for a cooker thermostat is through the use of a thermocouple. Thermocouples are switches with two types of coiled spring or straight wire metal ends that expand at different rates, depending on the ambient temperature. This results in closing a circuit to heat the unit when a temperature dial is set to a chosen point and opening it to shut off the device when that temperature is exceeded. One of the metals in a cooker thermostat thermocouple rotates with the temperature dial, and the other is fixed, resulting in efficient and accurate control of an oven based on expansion properties of the conducting metals.
Thermocouples are commonly used in heating systems in general. The most widespread use for them is in the design of a cooker thermostat, but they also are found in most furnace system controls and other devices that are designed to respond to temperature changes. A cooker thermostat relies on the established physical properties of the two metals that it uses, so it can function in the absence of a power source.
Conventional ovens primarily use cooker thermostats for the interior oven space. The burners on top of an oven, whether electric or gas-powered, typically are controlled by variable power setting on/off switches that are less accurate than a thermostat itself. This is why Fahrenheit and Celsius scale readings are printed on the interior oven control gauge, whereas the burner controls usually just list high, medium and low settings.
A cooker thermostat is integral to the functioning of a conventional gas or electric oven, so it is designed to be extremely reliable and built into the unit in such a way that it can be serviced only by qualified appliance personnel. In fact, an oven cannot function without a properly calibrated and working thermostat in place. It is the default on/off switch that gives the user complete control over the interior temperature of the oven, regardless of the outside temperature of the kitchen or cooking area itself.