Magnetic speed sensors use a magnet as the sensing element or sensed target in order to capture rotational or linear speed. Typically, they are used as gear-tooth speed sensors or incorporated into stroboscopes or tachometers. Technology choices magnetic speed sensors include magnetoresistive, inductive, variable reluctance, and Hall Effect. With magnetoresistive sensors, the resistance of the sensing element is a function of the direction and magnitude (proximity) of an applied magnetic field. With inductive sensors, an oscillator circuit generates a radio frequency (RF) electromagnetic field that radiates from a ferrite core and coil assembly. The field is directed at the sensor face. When a metal target enters the field, eddy currents are induced into the surfaces of the target. This causes a reduction in the amplitude of the oscillator circuit (change in inductance).

