Capacitor proximity sensors are actuated by which materials?

• A. Conductive materials only
• B. Non-conductive materials only
• C. Both conductive and non-conductive materials
• D. Magnetic materials

Answer: (C)

Capacitive proximity sensors actuate by detecting changes in capacitance as the target enters the sensor’s electric field. Any material that alters the dielectric environment around the sensing electrode will change the field and thus the measured capacitance. This includes non-conductive materials like plastics, glass, wood, or liquids, which have different dielectric constants than air. Conductive materials also influence the field because their presence can couple charges and significantly perturb the capacitance. Since both types of materials can cause a noticeable change in capacitance, capacitive sensors can sense both conductive and non-conductive targets. Magnetic materials aren’t the primary factor here, as that relates more to inductive sensing.