Passive Wheel Speed Sensors: Passive wheel speed sensors are commonly used to measure the rotational speed of the wheels. Its basic working principle: It consists of a set of electromagnets passing through a coil. When the protruding part of the gear tooth approaches the sensor magnet conductor, the magnetic flux increases; when the protruding part of the gear tooth leaves the magnet conductor, the magnetic flux decreases. The motion of the gear teeth results in a time-varying magnetic flux that induces a proportional AC voltage in the coil. This voltage is sent to the CPU, and its post-processing circuit converts the input signal into a digital pulse signal. The CPU measures the wheel speed according to the frequency change of the pulse signal.
Active sensor: An active sensor is a sensor that converts the measured current, magnetic field, displacement, pressure, differential pressure, speed, etc. into electromotive force output based on the Hall effect principle. The active wheel speed sensor is also composed of a sensing head and a ring gear. The sensor head is composed of permanent magnets, Hall elements and electronic circuits. The magnetic field lines of the permanent magnets pass through the Hall elements and lead to the gears. The magnetic field lines passing through the Hall elements are concentrated, and the magnetic field is relatively strong. When the gear rotates, the density of the magnetic lines of force passing through the Hall element changes, thus causing the Hall voltage to change, and the Hall element will output a quasi-sine wave voltage of millivolt (mV) level. This signal also needs to be converted into a standard pulse voltage by the electronic circuit.
Post time: Mar-15-2022