What is wheel speed sensor in vehicle?

The wheel speed sensor is used in ABS and Odometer. We can measure wheel speed by magnetic or optical method. Example for magnetic method is hall effect sensor. If we use hall effect sensor, it provides square wave output whose frequency is proportional to the wheel speed. The wheel speed sensor using hall technology incorporates the hall-sensing element, signal amplifier and signal processing all on a single chip. By changing magnetic field around the hall element induces alternating voltage. The alternating voltage is proportional to the changing magnetic field. The sinusoidal voltage is processed by the circuit into alternating digital output signal. The frequency of the current pulses are directly proportional to the wheel speed.