FAQ00302 of Proximity Sensors FAQ

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

1. Circuit composition

2. Principle of operation

That is called the high frequency oscillation type, the eddy current is generated on the metal surface by the metal's approaching the oscillation coil built into sensing surface, and the impedance of the detector coil changes by the electromagnetic induction action.

As a result, the oscillation circuit that oscillates in the high frequency cannot oscillate and the oscillation level decreases.

The approach of the sensing object is detected depending on the decrease degree at this oscillation level.

The eddy current is generated the higher the permeability of the sensing object like iron is, it is easy to for the sensor to detect it.