Which statement correctly identifies the problematic behavior of shielded capacitive proximity sensors in certain environments?

• A. They can trigger falsely due to dirt or moisture on the sensor face
• B. They never misread any target
• C. They are unaffected by surface contamination
• D. They only detect metal objects

Answer: (A)

Capacitive proximity sensing detects changes in capacitance caused by nearby materials, not just the presence of metal. A shielded version uses a guarded sensing field to focus on objects close to the face, but the dielectric properties of whatever sits on that face still matter. Dirt, dust, or moisture on the sensor surface forms a dielectric layer that alters the field and can imitate a target or push the reading over the threshold. That’s why environmental contamination on the sensor face can cause false triggers or unstable behavior. The shield helps against metal objects, but surface contamination remains a vulnerability, and capacitive sensors can respond to many non-metal materials, not only metals.