Operating principle of inductive sensors
The sensors take advantage of the physical effect of a change in the quality factor of a resonant circuit caused by eddy current losses in conductive materials. This is how it works: An LC tuned circuit generates a high frequency electromagnetic field. If a conductive material enters this field, eddy currents will be formed in accordance with the law of inductance which draw energy from the oscillator. This reduces the oscillation amplitude. The change is converted into a switching signal. This operating principle permits detection of all metals.