Movement sensor for magnetic object

摘要

The sensor has two measurement transducers (2a.2b) located opposite to a projection of magnetic material (1a) on a moving magnetic object, and a magnet (4), generating a polarising flux in the direction of the transducers. An imbalance in magnetic field sensitivity between transducers is generated by an asymmetrical polarising flux. A differential amplifier is used to amplify the difference between the transducer output signals. This is converted, in a signal shaping circuit, into a pulse signal which corresponds to the shape of the magnetic projection. The transducers are located at a specific distance apart in the direction (A) of the movement of the moving magnetic object (1), so that they detect a change in the magnetic flux created by the movement of the projection. The asymmetrical polarising flux subjects each transducer to a different flux level. The difference in their signal levels corresponds to the difference in amplitude of the magnetic flux, which is greater than the hysteresis of the shaping circuit.