Patent ID: 8179124

Claim:
An inductive proximity sensor for embedding in a metal mounting plate, comprising an enclosure with a front wall of synthetic material forming a sensing face at a front end of the enclosure, an oscillator comprising a sensor coil with a core consisting of a material with a relative magnetic permeability larger than 1, typically a ferrite, which is arranged within the enclosure behind the front wall so that an open side of the core is directed towards the sensing face in order to direct the magnetic field of the coil towards a target in front of the sensing face, a hollow cylindrical metal member arranged perpendicular to the sensing face and surrounding the core, and a measuring circuit for measuring an attenuation of the oscillator due to eddy currents, wherein the core is radially surrounded by a metal layer with an electrical resistivity of less than 15 μ□cm and with a thickness of less than 40 μm, wherein the measuring circuit is arranged to change an output signal of the sensor circuit as soon as the attenuation exceeds a predetermined reference threshold corresponding to an attenuation of 0.1 (10 percent) or less.