Which device is typically actuated by a mechanical plunger or lever in industrial automation?

• A. Limit switch
• B. Proximity sensor
• C. Temperature switch
• D. Photoelectric sensor

Answer: (A)

A limit switch is designed to be activated by a physical actuator like a plunger or lever. When a moving part presses the plunger or pushes the lever, the internal contacts change state, signaling end-of-travel, position, or an interlock. This direct mechanical actuation makes limit switches ideal for robust position sensing in machines and safety interlocks.

Proximity sensors detect or respond to nearby objects without contact, using magnetic, capacitive, or inductive fields, so they’re not typically driven by a mechanical plunger. Temperature switches respond to heat, changing state when a set temperature is reached. Photoelectric sensors use a light beam and detect interruptions or reflections, not mechanical depression.