PURPOSE: To obtain a measuring apparatus which can operate conveniently over a wide frequency band while facilitating manufacture of a coil by arranging second members on the opposite end faces of a first member where corresponding cores are arranged with winding coils.

CONSTITUTION: Cores 12, 13 constituting a coil body 11 have D-shaped cross-section and arranged on a holder 14. The cores 12, 13 are applied with winding coils 15, 16 and the measuring apparatus can be applied to a wide range of holder frequency range from 5kHz to 5MHz, for example, by simply varying the diameter and the number of turns of the winding. Semicircular discs 19, 20 movable relatively to the coil body 11 are arranged on the opposite end faces of the coil body 11 while being fixed to a shaft 18 and an AC field induced in the coils 15, 16 by an AC current induces eddy currents on the metal surface of the discs 19, 20. The discs 19, 20 are turned in parallel with the end face of the coil body 11 and the eddy current increases as the field surface penetrating the discs 19, 20 increases. The eddy current varies the AC resistance of the coil and the variation is utilized for obtaining a measurement signal. Variation in the inductance of the coil is also utilized.