Which statement best describes a limit switch?

• A. A sensor used to measure distance to a target.
• B. A fixed-position sensor used to stop a mechanism or determine home position.
• C. A device that stores energy for movement.
• D. A sensor used to detect ambient light.

Answer: (B)

A limit switch is a fixed-position sensor that is triggered when a moving part reaches a defined point, signaling the controller to stop the mechanism or to establish a home/reference position. It usually has a small actuator, like a plunger or lever, that the moving part presses, changing the electrical state to indicate the limit has been reached. This makes it ideal for defining end-of-travel points and ensuring the robot returns to a known starting position for repeatable motion and safety. It’s not used to measure distance to a target, store energy, or detect ambient light, which are functions of distance/position sensors, energy storage devices, and light sensors, respectively.