Egner, H.H.EgnerRus, R.R.RusAnthonio, P.P.Anthonio2022-03-082022-03-081994https://publica.fraunhofer.de/handle/publica/303115The description relates to an eddy current sensor comprising a measuring coil in whose magnetic field the object to be sensed is arranged, a reference coil and a sine-wave generator, whose output signal is applied to the coils, whose output signal is subtracted by means of a subtractor, whose output signal is directly applied to a first demodulator and to a second demodulator via a 90 degree phase shifter, whereby an additional signal is applied to the demodulators in the form of the sine-wave generator output signal shifted by an adjustable phase angle via phase shifter, said phase angle being selected so that interference signals have a specific direction in the complex impedance plane. The sensor according to the invention is characterized by the output signal of the first demodulator being applied via an amplifier having an adjustable gain factor (a) and the output signal of the second demodulator being applied via an amplifier having an adjustable gain factor (b) to a further subt ractor, whose output signal (U<t<r<i<g) e.g. is added via a trigger threshold and acts as a standard for the object to be sensed.de608670patent1988-3817574