Which device is defined as a sensor able to detect objects without physical touch?

• A. A sensor that measures temperature
• B. A camera-based detection system
• C. A proximity sensor
• D. A pressure transducer

Answer: (C)

Detecting objects without touching them is the hallmark of non-contact presence sensing. A proximity sensor is designed to sense the presence or absence of nearby objects without physical contact, using methods such as inductive, capacitive, infrared, or ultrasonic sensing. It triggers when a target enters its sensing range, making it ideal for counting parts, detecting end stops, or safety interlocks without wear from contact.

Temperature sensors measure a physical property (temperature) at a point, and pressure transducers measure pressure, not object presence. A camera-based detection system can also identify objects without touching them, but it’s primarily an imaging device and relies on visual processing rather than a dedicated non-contact proximity-detection function.