The physical mode of action is based on the eddy current effect. A high frequency magnetic field generated by the measuring coil (sensor) induces eddy currents in the electrically conductive material to be detected. This equates to a power loss in the coil or an increased attenuation. An analysis is made of the resonance resistance of the resonant circuit which changes with the distance of the sensor to the measured object.
A special temperature compensation optimizes the temperature stability of the sensor. All electrically conductive materials are suitable as measuring media. Optimal measurements are achieved on ferromagnetic materials. The sensors are wear- and maintenance-free. Environmental influences from water, oils, emulsions and electromagnetic interference fields do not affect measurement accuracy.