Advanced Braking
Wheel Speed Sensor
Active wheel speed sensors have been in use since 1999 on models using the Teves Mark 20e system.
The Teves Mark 25, Teves Mark 25e, TRW EBC-340, some EBC-125 and the late model Bosch systems use this style sensor as well. This style sensor helps increase performance, durability and low speed accuracy. In other words, these sensors do not seem to have the false cycle problem like the passive sensors do.
Most vehicles with active sensors still use a toothed tone wheel which acts as the trigger mechanism for the sensor.
These have north/south pole magnets imbedded into the ring. The ring is then pressed on the axle shaft just like a tone wheel. In either case the result is a digital square wave signal.
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