Regular rotational speed measurement methods include magnetic field method, vibration method and the optical method. As a type of non-contact measurement, magnetic field method detects the magnetic field strength change via magnetic sensor. Thus confirm rotational speed according to the time between the signal pulses. Magnetic sensor for rotational speed measurement contains the Hall Effect sensor, induction coil sensor and magnetoresistance sensor. Magnetoresistance speed sensor has many advantages compared with induction coil sensor and Hall Effect sensor, include:
- Zero-speed measurement.
- Wideworking
- Relatively wide working frequency which between 0 and 25 kHz.
- Wide working temperature ranges.
- Powerful capability of electromagnetic interference resistance.
Working Principle of Magnetoresistance Speed Sensor
The most representative application of Magnetoeresistance speed sensor is the rotational speed of the gear wheel. Magnetoresistance speed sensor can be classified into active-type and passive-type. Ferromagnetic material gear wheel need to use passive-type speed sensor which collected disturbance signal around sensitive chip caused by rotation of convex teeth and concave teeth, and then got the gear wheel rotational speed. Active-type application is mainly for non-magnetic material rotor, and periodic magnetized magnet should surround the rotor. Magnetic field of the multi-pole magnet will rotate when rotor rotating, therefore, the output signal will be changed due to the periodic change in the magnetic field which acted on magnetoresitance sensor.
About Speed Sensor Magnet
The output signal amplitude of the sensor is depended on the magnetic field strength provided by the speed sensor magnet, air gap and gear wheel shape. Obviously, increase magnetic field strength of speed sensor magnet or decrease distance between sensor and gear wheel is conductive to the enhancement of output signal amplitude. SDM professional technical team will provide enough technical support during the project development, and we also collected much experience in the quality control via ABS wheel speed sensor magnet.
