What type of surfaces are INDUCTIVE prox sensors able to detect?

• A. Non-metallic
• B. Ferrous (metallic)
• C. Wood
• D. Plastic

Answer: (B)

Inductive proximity sensors sense metal by using a magnetic field. The coil inside the sensor creates an alternating magnetic field; when a metal surface comes near, the field induces currents in the object and the material’s magnetic properties alter the field. This causes a change in the coil’s impedance, which the sensor detects and uses to indicate presence. Ferrous metals have high magnetic permeability, so they interact with the field more strongly and produce a larger, more reliable change. Non-metallic surfaces like wood or plastic don’t interact with the magnetic field in this way, so they aren’t detected by standard inductive sensors. Some specialized designs can sense non-ferrous metals, but the typical, robust detection is ferrous (metallic) surfaces.