Wheel Speed Sensor: Description and Operation

GF42.45-P-4550-02SK Wheel speed sensor, function

Function of the active wheel speed sensor
The strength and direction of an external magnetic field causes a change in the internal resistance inside the sensor. Via an electronic analysis system accommodated in the sensor a square-wave signal is produced, the frequency of which depends on the rotational speed but the amplitude of which is constant. Due to a different signal pattern when the wheel is moving to the left or right the direction of travel is detected. This signal is read in by the ESP and BAS control unit (N47-5) and placed on the Controller Area Network bus class B (interior) (CAN-B).

The external magnetic field is produced by a multipole ring. This consists of an elastomer plastic in which metal particles are incorporated. Via a special magnetization process they are aligned so that various magnets arise, the polarity of which changes from North to South.