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Key Components of Building Automation Systems

Modern control systems have three necessary elements: sensors, controllers, and the controlled devices.

Component	Description
Sensors	There is an increasing variety and level of sophistication of sensors available for use with modern control systems. Some of the more common include: temperature, humidity, pressure, flow rate, and power. Sensors that track indoor air quality, lighting level, and fire or smoke are becoming more common.
Controllers	The function of the controller is to compare a signal received from the sensor to a desired setpoint, and then send out a corresponding signal to the controlled device for action. Controllers may be very simple, such as a thermostat where the sensor and controller are usually co-located, to very sophisticated microprocessor based systems capable of powerful analysis routines.
Controlled Devices	The controlled device is the terminal device receiving the signal from the controller. Amongst others, typical controlled devices include: air dampers, mixing boxes, control valves, and in some cases, fans, pumps, and motors.