An inductive proximity sensor detects metallic objects by which principle?

An inductive proximity sensor detects metallic objects by which principle?

• A. Optical reflection
• B. Ultrasonic echo
• C. Electromagnetic induction
• D. Capacitive coupling

Answer: (C)

Inductive proximity sensing relies on electromagnetic induction. The sensor drives a coil to generate a changing magnetic field. When a metallic object enters that field, eddy currents are induced in the metal. These currents create a magnetic field that opposes the original field, changing the coil’s impedance (or the oscillator frequency). The sensor detects this change and signals the presence of metal. Other methods rely on light (optical reflection), sound waves (ultrasonic echo), or changes in capacitance with dielectrics, which don’t respond to metallic objects in the same way.

Inductive proximity sensing relies on electromagnetic induction. The sensor drives a coil to generate a changing magnetic field. When a metallic object enters that field, eddy currents are induced in the metal. These currents create a magnetic field that opposes the original field, changing the coil’s impedance (or the oscillator frequency). The sensor detects this change and signals the presence of metal. Other methods rely on light (optical reflection), sound waves (ultrasonic echo), or changes in capacitance with dielectrics, which don’t respond to metallic objects in the same way.