Which device is typically used as a digital input (on/off)?

Which device is typically used as a digital input (on/off)?

• A. Limit switch
• B. Potentiometer
• C. Bumper switch
• D. Ultrasonic sensor

Answer: (A)

Digital inputs provide a binary signal—either on or off. A limit switch is a rugged mechanical switch designed to change contact states when a moving part reaches a specific position, giving a clear, definite on/off signal that controllers can read reliably. This makes it a classic choice for detecting end stops, home positions, or safety interlocks in automation. Potentiometers are fundamentally analog; their resistance varies continuously with position, which requires analog-to-digital conversion to become a digital input. Ultrasonic sensors measure distance and typically output a distance value (or a pulse echo), not a simple binary state, so they’re used for measurement rather than a straightforward on/off input. A bumper switch is also a binary switch and can serve as a digital input, but limit switches are the standard for fixed-limit detection because of their robustness, defined actuation points, and suitability for harsh environments.

Digital inputs provide a binary signal—either on or off. A limit switch is a rugged mechanical switch designed to change contact states when a moving part reaches a specific position, giving a clear, definite on/off signal that controllers can read reliably. This makes it a classic choice for detecting end stops, home positions, or safety interlocks in automation.

Potentiometers are fundamentally analog; their resistance varies continuously with position, which requires analog-to-digital conversion to become a digital input. Ultrasonic sensors measure distance and typically output a distance value (or a pulse echo), not a simple binary state, so they’re used for measurement rather than a straightforward on/off input. A bumper switch is also a binary switch and can serve as a digital input, but limit switches are the standard for fixed-limit detection because of their robustness, defined actuation points, and suitability for harsh environments.