Wheel Speed Sensor: Description and Operation

GF42.45-P-5134RC Wheel rpm sensor, component description





Location
The front rpm sensors are mounted on the left and right front axle steering knuckles. The rear rpm sensors are mounted on the left and right wheel carriers of the rear axle.

Task
Standstill, direction of rotation and rpm of the wheels are recorded via the rpm sensors.

The signals of the rpm sensors are read in discretely by the ESP and BAS control unit (N47-5).

Function
The rpm sensor is a magneto resistive sensor element (active wheel rpm sensor) and changes its resistance depending on the magnetic field applied to it externally (multipole ring on wheel).

The ESP and BAS control unit measures the current it supplies to the rpm sensor. Depending on the position of the multipole ring (negative pole or positive pole), a current strength of I = 7 mA or I = 14 mA is measured, producing a square wave signal. The ESP and BAS control unit derives the wheel speed from this square wave signal.