Abstract: A method and device is disclosed whereby the number of revolutions of an axle or the angle of rotation of an axle are represented by a particular value. The value is preferably in the form of an electric analog signal. A pickoff element having a linearly-shaped primary coil and a linearly-shaped secondary coil is disposed so that the primary and secondary coils are in parallel with an air gap therebetween. The air gap is for the formation of a homogeneous stray field. A metallic disc which has a rim in the form of an Archimedes' spiral, is affixed to an axle. The disc is disposed in the air gap between the primary and secondary coils. A high frequency signal is supplied to the primary coil. Accordingly, when the axis is rotated, an amplitude modulated signal is developed at the secondary coil. The amplitude modulated signal is then demodulated and subsequently differentiated to provide an analog signal proportional to the angular rotation of the axle or the number of revolutions of the axle.