Which term describes a device that detects objects without physical contact and is commonly used in automation?

• A. Ultrasonic sensor
• B. Proximity sensor
• C. Photoelectric sensor
• D. Capacitive sensor

Answer: (B)

Detecting objects without physical contact in automation is described by the term proximity sensor. This category covers devices that sense presence or distance without touching the item, making them ideal for fast, wear-free detection on conveyors, robots, and assembly lines. Proximity sensors use various sensing principles—inductive (metal targets), capacitive (non-metal targets), photoelectric (light beam), and ultrasonic (sound waves)—yet share the common feature of non-contact detection, which is why this broad term fits the question best. The other options refer to specific non-contact sensing technologies, but the overarching label that describes the device type is proximity sensor.