Actuator is a functional element, which connects the information processing part of an electronic control system with a technical or non-technical process. Actuator can be used to control the flow of energy, mass or volume. The actuator control is always achieved using very low electrical power, ideally without any power consumption, with currents and voltages which are, if possible, microelectronically compatible. As an actuator is supposed to control flows of matter and energy, an actuator must contain at least one energy controller. An actuator contains series connection of an energy controller and an energy converter. The term actuator refers often only to the energy converter, whereas the energy controller is called a power amplifier or power circuit.

The electric actuator has a motor drive that provides torque to operate a valve. Electric actuators are frequently used on multi-turn valves such as gate or globe valves. With the addition of a quarter-turn gearbox, they can be utilized on ball, plug, or other quarter-turn valves. A single or three-phased electric motor drives a combination of spurs and/or level gears, which in turn drive a stem nut. The stem nut engages the stem of the valve to open or close it, frequently via an Acme threaded shaft. To protect the valve, the limit switch turns off the motor when it stops. The torque sensing mechanism of the actuator switches off the electric motor when a safe torque level is exceeded. Position indicating switches are utilized to indicate the open and closed position of the valve.

Actuator is a mechanical device used for moving or controlling a mechanism or system. Remote mounted actuator is available for most damper control applications. It can be used to control the flow of energy, mass or volume.