FAQ00397 of Proximity Sensors FAQ

The circuit composition and the principle of operation are as follows.

1. Circuit composition

2. Principle of operation

When the metal or the dielectric approaches the electrode, the capacitance between a main electrode and ground potential increases by the effect of the electrostatic induction.

The CR oscillation circuit that starts oscillation depending on the capacitance change of this electrode is composed, and the approach of the sensing object is detected by increase of the oscillation amplitude.

When the sensing object is the dielectric, the change in the capacitance between a main electrode and ground potential grows by the relative permittivity large and it is easy for the sensor to detect it.