Wheel Speed Sensors

Basic Description

Wheel Speed Sensors measure the road-wheel speed and direction of rotation. These sensors provide input to a number of different automotive systems including the anti-lock brake system and electronic stability control. Wheel speed sensors typically include a toothed (or optically encoded) shaft and a magnetic (or optical) sensor. The sensor counts the rate at which the teeth or marks pass by. Wheel speed sensors may monitor the crankshaft or driveshaft rotation in vehicles that do not need to know the rate at which individual wheels are turning. Otherwise, they monitor the rotation of the axle driving each wheel.

There are two types of magnetic sensors: variable reluctance and Hall effect. Both types detect the teeth of a steel gear as it rotates beneath the sensor. Variable reluctance sensors detect the change in the inductance of a wire coil as a steel tooth comes into close proximity. Hall effect sensors measure the change in the resistance of a semiconducting slab due to the strength of an applied magnetic field.

Manufacturers

ATE, Beru, Bosch, Continental, Gill, Honeywell

For More Information

[1] Hall Effect Sensor, Wikipedia.

[2] Wheel Speed Sensor, Wikipedia.