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A good example of this is a central heating boiler controlled only by a timer, so that heat is applied for a constant time, regardless of the temperature of the building. The control action is the switching on/off of the boiler, but the controlled variable should be the building temperature, but is not because this is open-loop control of the ...
Honeywell electronic thermostat in a store. Heating and cooling losses from a building (or any other container) become greater as the difference in temperature increases. A programmable thermostat allows reduction of these losses by allowing the temperature difference to be reduced at times when the reduced amount of heating or cooling would not be objectionable.
A time switch (also called a timer switch, or simply timer) is a device that operates an electric switch controlled by a timer. Intermatic introduced its first time switch in 1945, which was used for "electric signs, store window lighting, apartment hall lights, stokers, and oil and gas burners." A consumer version was added in 1952.
A typical kitchen timer. A timer or countdown timer is a type of clock that starts from a specified time duration and stops upon reaching 00:00. An example of a simple timer is an hourglass. Commonly, a timer triggers an alarm when it ends. A timer can be implemented through hardware or software.
A good example of this is a central heating boiler controlled only by a timer, so that heat is applied for a constant time, regardless of the temperature of the building. The control action is the switching on/off of the boiler, but the controlled variable should be the building temperature, but is not because this is open-loop control of the ...
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A Piping and Instrumentation Diagram (P&ID) is a detailed diagram in the process industry which shows process equipment together with the instrumentation and control devices.
Another consideration is the time delay of the controlled system. To improve the control performance of the system, thermostats can include an "anticipator", which stops heating/cooling slightly earlier than reaching the setpoint, as the system will continue to produce heat for a short while. [4]