English 
how does a mechanical speedometer work
A purely mechanical speedometer odometer consists of a worm gear mechanism and a digital wheel. When the car is running, the driving gear (worm gear) of the odometer installed on the main shaft of the gearbox drives the driven gear (worm) of the odometer to rotate, and the worm drives the flexible steel wire shaft, and the flexible steel wire passes through the worm gear on the instrument panel to rotate the counter to display the odometer number.
Mechanical-electronic speedometer: Mechanical-electronic odometer (installed on the worm of the gearbox worm gear assembly on the wheel, there are photoelectric and magnetoelectric). When the car is running, the odometer passive gear drives the magnetic steel in the electronic odometer sensor to make a circular motion, and the electronic odometer sensor outputs N (generally 8 or 10) pulse signals every time the magnetic steel rotates. The wiring harness goes to the speedometer.The transmitted photoelectric pulse or magnetoelectric pulse signal can display the vehicle speed on the display screen after being processed by the microcomputer inside the instrument. The odometer is calculated and displayed by the microcomputer according to the speed of the vehicle and the accumulated running time.
Pure electronic speedometer: The pure electronic odometer sensor is not in direct contact with the mechanical parts, and there is a certain gap between the sensor probe and the target wheel, which is generally controlled at 1.4+0.6mm. When the car is running, the odometer rotor rotates together with the output shaft of the transmission. When a certain tooth of the odometer rotor rotates to the position corresponding to the sensor probe, the sensitive device in the probe outputs a low level under the action of the odometer rotor magnetic field. The tooth of the odometer rotor is not aligned with the sensor probe, and the sensitive device in the probe is not affected by the magnetic field and outputs a high level. In this way, the odometer sensor will output a square wave pulse signal every time the output shaft of the transmission rotates. For the speedometer, the magnetoelectric pulse signal sent by the sensor can display the vehicle speed on the display after being processed by the microcomputer inside the instrument. The odometer is calculated and displayed by the microcomputer according to the speed of the vehicle and the accumulated running time.
Get a Quote / Info