What type of signal is most commonly used to communicate wheel speed information to the ABS control module?

A pulse signal, either from a magnetic reluctance sensor or a Hall effect sensor, is the type of signal most commonly used to communicate wheel speed information to the ABS control module. Wheel speed sensors are located at each wheel and generate a signal that corresponds to the wheel's rotational speed. Magnetic reluctance sensors generate an AC voltage signal whose frequency is proportional to wheel speed. As the wheel rotates, a toothed wheel (reluctor ring) passes by the sensor, inducing a voltage in the sensor coil. The faster the wheel rotates, the higher the frequency of the AC signal. Hall effect sensors use a magnetic field and a semiconductor to generate a digital pulse signal. As the wheel rotates, a rotating exciter ring with magnets passes by the sensor, causing the sensor to switch on and off, producing a series of pulses. The frequency of these pulses is proportional to the wheel speed. Both types of sensors provide the ABS control module with the necessary information to monitor wheel speed and detect impending wheel lockup. While the signal generation differs, the key is that the ABS module interprets the frequency of the pulse signal from either sensor to determine the speed of each wheel.