a variable reluctance sensor is disclosed as adapted for sensing the rate of revolution of a toothed wheel of magnetic material . the sensor has at least two magnets disposed side by side . one of the magnet has a first pole disposed opposite the toothed wheel , and the other magnet has a second pole disposed opposite the toothed wheel . the second pole of the first mentioned magnet and the first pole of the second magnet are both held against a magnetic core around which a coil is wound . as the teeth of the magnetic wheel successively travel past the magnets , they create magnetic fluxes oriented in opposite directions , which counteract each other in the core . consequently , the total magnetic flux in the magnetic member varies more greatly than heretofore depending upon whether each magnet is opposed to any one tooth , or to the space between any two neighboring teeth , of the magnetic wheel . such great variations in magnetic flux are translated into a correspondingly large amplitude signal as by the coil around the core .