Thermostat
A thermostat regulates temperature by switching a heating or cooling system on and off in response to measured conditions or a setpoint.
Feedback control: A control method that measures a system’s output and adjusts its input to reduce deviation from a target. A thermostat uses temperature feedback to decide when its controlled system should run.
Thermistor: A resistor whose electrical resistance changes substantially with temperature. Electronic thermostats often use thermistors as compact temperature sensors.
Central heating: A system that produces heat at a central source and distributes it through a building. A room thermostat commonly calls the central heating system to maintain indoor temperature.
Proportional control: A control method whose output varies in proportion to the difference between measured and target values. Unlike simple on-off switching, proportional control can vary heating or cooling output with temperature error.
Heating, ventilation, and air conditioning: Building systems that provide heating, cooling, ventilation, and often humidity control. Thermostats coordinate demand within HVAC systems and influence how those systems operate.
Hysteresis: A system’s state depends partly on its history, producing different switching thresholds when conditions rise or fall. Separate turn-on and turn-off temperatures prevent rapid cycling around the setpoint.
Bimetallic strip: Two bonded metals that bend as temperature changes because they expand at different rates. Mechanical thermostats can use its bending to open or close electrical contacts.
Air conditioning: The treatment of indoor air to control properties such as temperature, humidity, and cleanliness. Thermostats switch cooling equipment when indoor temperature exceeds its target.
PID controller: A controller that combines proportional, integral, and derivative responses to control a process. PID control can regulate temperature more continuously than a basic thermostat’s switching.
Energy efficiency: The ability to provide a service while using less energy. Temperature targets and schedules can change how much energy thermostat-controlled equipment consumes.