Abstract: In a metal body discriminating apparatus of a simple structure and a high detecting accuracy for discriminating a material, a shape, a size, or the like of a metal body by the magnetical principle, an oscillator which performs the oscillating operation by the resonant operation together with the coil wound like a ring is provided to thereby generate magnetic lines of force in the coil. Changes in frequency and amplitude of an oscillation signal in response to changes in impedance and inductance of the coil by the operation of the eddy current which is generated in the metal body by the magnetic lines of force by relatively moving the metal body into the hollow space of the coil are detected as feature parameters of the metal body. Two or more coils constructing a similar oscillator are arranged at regular intervals and a size of metal body is discriminated from each of the oscillation signals having a phase difference which are obtained when the metal body passes in the coils with a time deviation.

Abstract: In a metal body discriminating apparatus for discriminating the material, shape, size, or the like of a metal body, an oscillator performs a self-oscillating operation together with a coil wound like a ring provided to generate magnetic lines of force. Changes in frequency and amplitude of an oscillation signal in response to changes in impedance and inductance of the coil caused by an eddy current, which is generated in the metal body when the metal body moves through the coil, are detected as indicators of features of the metal body. Two or more of such coils may be arranged at regular intervals and the size of metal body will be discriminated based on signals having a phase difference which are obvious when the metal body passes sequentially through the coils.