ITPEC FE Morning April 2019 Question 21

Turns an electrical control signal into mechanical motion — an actuator is the output side of a control system, acting on the physical world.

A computer control loop has two ends. A sensor measures a physical quantity such as temperature or position and turns it into an electrical signal. The computer processes that signal and sends a control signal to an actuator, such as a motor, solenoid or valve, which turns it into physical movement.

Answer (b)

Why not others:

• •(a) — converting an analog electrical signal to digital is an A/D converter
• •(c) — detecting a physical quantity and turning it into an electrical signal is a sensor, the opposite of an actuator
• •(d) — keyboards and touch panels are input devices that let a person enter data

Key rule: Sensors turn the physical world into signals for the computer; actuators turn the computer's signals back into physical action.

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