How Wheel Speed Sensors Work The difference between vehicle speed and wheel speed sensors

Passive wheel speed sensors are typically used to measure wheel rotation speed and operate on a basic principle: a set of electromagnets passing through a coil.

Compose. The magnetic flux when the protruding part of the tooth is close to the sensor conductor.

Increase; When the protruding part of the tooth leaves the conductor, the magnetic flux decreases. As a result of the movement of the teeth, the magnetic flux changes over time, and a proportional AC voltage is induced in the ring. This voltage is delivered to the CPU, where the post-processing circuitry converts the input signal into a digital pulse signal.

The CPU measures the wheel speed based on the frequency change of the pulse signal. Active Sensors Active sensors are based on the Hall effect.

The principle converts measurements, such as current, magnetic field, displacement, pressure, differential pressure, rotational speed, etc., into electromotive force.

An output of a sensor. The active wheel speed sensor also consists of a sensing head and a ring gear. The sensing head is composed of permanent magnets, Hall elements and electronic circuits, etc., and the magnetic field lines of the permanent magnet lead to the gear through the Hall element, and the magnetic field lines through the Hall element are concentrated, and the magnetic field is relatively strong.

When the gear rotates, the density of the magnetic field lines passing through the Hall element changes, causing a change in the Hall voltage, and the Hall element will output a quasi-sine wave voltage in the millivolt (mV) range. This signal also needs to be converted into a standard impulse voltage by the electronic circuit.

The role of the wheel speed sensor is to measure the speed of the wheels of the car. The wheel speed sensor detects the frequency signal of each wheel rotation **speed signal), and then transmits this signal to the ABS computer. When the speed reaches the set value, the emergency brake brakes and the ABS system starts to work.

When the ABS computer controls the wheel to brake and loosen, the wheel speed sensor will detect the distance signal of the tire from braking to rotation, so that the ABS controls the brake to achieve the best braking distance. Common wheel speed sensors mainly include magnetoelectric wheel speed sensors and Hall wheel speed sensors.

Magnetoelectric wheel speed sensors are designed using the principle of electromagnetic induction. It has simple structure, low cost, is not afraid of mud, does not need power supply, and is widely used in ABS anti-lock braking system. However, at the same time, there are also some disadvantages, such as low frequency response, when the speed is too high, the frequency response of the sensor can not keep up, and it is easy to produce false signals.

There is also poor anti-electromagnetic interference ability. The oscilloscope measures a sine wave, and the higher the wheel speed, the greater the output signal voltage amplitude.

Hall-style wheel speed sensorIt is made by using the principle of Hall effect, and its output signal voltage amplitude is not affected by speed, with high frequency response and strong anti-electromagnetic interference ability, but there must be power supply. Let's take this sensor as an example to measure:

First of all, connect a BNC to banana head wire to one channel of the oscilloscope, connect the red head to the stinger for the positive pole, connect the signal line of the sensor, and connect the black head to the crocodile clip or the stinger to the negative electrode ground.

Open the oscilloscope channel menu, set the channel attenuation ratio to 1x, adjust the vertical gear to 1V div, and hit the time base to about 10ms, and then adjust it according to the actual situation.

Since the Hall wheel speed sensor is powered by a power supply, the observed waveform should have a direct current of about 11-12V at this time.

The vehicle is erected with a jack, the wheels are turned, and the output waveform of the sensor signal is measured with the car oscilloscope.

The Hall effect sensor consists of an almost completely closed magnetic circuit of a permanent magnet or pole, a soft magnetic impeller turns through the gap between the magnet and the pole, when the window on the impeller allows the magnetic field to pass through and transmit unhindered to the Hall effect sensor, the magnetic field is interrupted (because the blade conducts the magnetic field to the sensor), the impeller allows the magnetic field to pass through and block the magnetic field when the window is open and closed, causing the Hall effect sensor to turn on and off like a switch, That's why some automakers refer to Hall-effect sensors and some other similar electronic devices as Hall switches, which are actually switchgears. Therefore, the signal waveform of the Hall effect sensor is actually one pulse after another, that is, a square wave.

The faster the wheel speed, the faster the frequency of the signal waveform, but the AC voltage value remains the same, from 0V to 1V. If you slow down the rotation of the wheels, you can see that the frequency of the signal waveform decreases.

If the digital ABS sensor has only a 0 volt output at all times, it should first be checked to see if it has a power supply**. Then confirm that the signal frequency of this sensor closely follows the wheel speed, otherwise it means a malfunction.

Hello, wheel speed sensors are generally divided into magnetoelectric and magnetoresistive, one is contact, has been non-contact, magnetoelectric is the use of the principle of magnetism, the signal disk rotates and cuts the magnetic inductance line to generate AC voltage, the reluctance is the signal disk to change the strength of the magnetic field, thereby changing its internal resistance to produce electrical signals, I hope it will help you.

After the signal of the speed mileage sensor is transmitted to the odometer, the odometer determines how much mileage has been traveled according to the signal, and the position is at the second axis of the output shaft of the gearbox.

The wheel speed sensor is the vehicle speed mileage sensor.

How the wheel speed sensor works; When the rotor mounted on the output shaft turns, an alternating voltage is generated in the wheel speed sensor coil and sent to the ECU, which controls the timing of gear shifts and locks based on the signals from this wheel speed sensor and the throttle position sensor

1.The functions of the wheel speed sensor are as follows:1A wheel speed sensor is a sensor used to measure the rotational speed of a car's wheels.

2.Generally speaking, all vehicle speed sensors can be used as wheel speed sensors; 2.However, considering the actual factors such as the working environment and space size of the wheel, the commonly used wheel speed sensors mainly include magnetoelectric wheel speed sensors and Hall wheel speed sensors; 3.

The magnetoelectric wheel speed sensor is designed based on the principle of electromagnetic induction.

3.It has the characteristics of simple structure, low cost and not afraid of mud, and is widely used in ABS anti-lock braking system of modern automobiles.

4,4.But magnetoelectric wheel speed sensors also have some drawbacks: low frequency response.

5.When the speed of the vehicle is too high, the frequency rate response of the sensor cannot keep up, and it is easy to produce false traces to eliminate the signal; Poor immunity to electromagnetic interference, especially when the output signal amplitude is small.