What is an actuator?

• A. Measures temperature changes.
• B. Converts electrical energy to light.
• C. Records process data.
• D. Provides power and motion to manipulate moving parts of a valve or damper used to control fluid flow through a final element.

Answer: (D)

An actuator is the component that provides the actual motion in a control loop by turning energy into movement. It takes the control signal from the controller and uses electrical, pneumatic, or hydraulic energy to move a valve stem or damper blade, which then adjusts the fluid flow through the final control element. This is why it’s described as providing power and motion to manipulate moving parts that control flow.

The other ideas describe sensors or devices that do not move the control element: measuring temperature, producing light, or recording data.