The eddy current principle finds applications in the measurement of electrically conductive materials that may have ferromagnetic or non-ferromagnetic characteristics. A coil is integrated in a sensor housing and energised by a high-frequency alternating current. The coil’s electromagnetic field induces eddy currents in the conductive Measurement object , causing the resulting alternating current resistance of the coil to change. This change of impedance causes an electrical signal which is proportional to the distance of the Measurement object to the sensor coil. Eddy current sensors enable non-contact and wear-free distance measurements against metallic objects. Eddy current technology provides measurements in the nanometre range. The high-frequency field lines emanating from the sensor coil easily penetrate non-metallic materials, which allows for measurements even at high levels of contamination, pressure and oil. This special characteristic enables furthermore to measure on metallic objects covered with plastics which is why e.g. layer thicknesses can be detected.