What types of surfaces are CAPACITIVE prox sensors able to detect?

• A. Metallic only
• B. Non-metallic only
• C. Metallic and non-metallic
• D. Wood

Answer: (C)

Capacitive proximity sensing relies on changes in capacitance caused by the presence of a nearby object in the sensor’s electric field. Any material with a dielectric constant different from air will perturb that field and alter the sensed capacitance. Metals cause a strong change because of their conductivity and high polarizability, while non-metallic materials like plastics, wood, glass, or liquids also affect the field through their dielectric properties. Since detection depends on these dielectric changes rather than just conductivity, capacitive sensors can detect both metallic and non-metallic surfaces. The strength of the response and the practical detectability depend on material properties, size, and distance from the sensor.