Linear ABS wheel speed sensor: the linear wheel speed sensor is mainly composed of permanent magnet, pole axis, induction coil and gear ring. When the ring rotates, the crown and backlash alternately face the polar axis. During the rotation of the gear ring, the magnetic flux inside the induction coil alternates to generate the induced electromotive force, which is input to the ECU of ABS through a cable at the end of the induction coil. When the speed of the gear ring changes, the frequency of the induced electromotive force changes.