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how speedometer works
The speedometer sensor is installed in the combination instrument and driven by the transmission through the flexible shaft. When the car is driving, it generates a signal proportional to the driving speed of the car. The utility model is composed of a tongue spring switch and a rotor with one or several pairs of contacts. Signal processing signal processing circuit consists of monostable trigger circuit, constant current circuit, 64 frequency division circuit, power amplification circuit, power supply voltage stabilization and other electronic circuits. When the vehicle is running, it transforms the pulse signal input by the speed sensor into a current signal and amplifies it to drive the speedometer to indicate the speed; At the same time, it also converts the pulse signal into a pulse signal of a certain frequency through frequency division and power amplification to drive the shaft of the odometer stepper motor.
The traditional speedometer is mechanical. A typical mechanical odometer is connected to a flexible shaft. There is a steel cable in the flexible shaft. The other end of the flexible shaft is connected to a gear of the transmission. The rotation of the gear drives the steel cable to rotate. The steel cable drives a magnet in the odometer cover ring to rotate. The cover ring is connected with the pointer and sets the pointer to zero through the hairspring.The speed of magnet rotation causes the change of magnetic line of force. The balance is broken and the pointer is driven. The speedometer is simple and practical, and is widely used in large and small cars. However, with the development of electronic technology. Now many car instruments have used electronic speedometer. The common one is to obtain the signal from the speed sensor on the transmission and deflect the pointer or display the number through the change of pulse frequency.Odometer is a digital instrument, which makes the counter drum rotate by meshing the transmission gear of the counter drum with the worm on the transmission shaft of the speedometer. The utility model is characterized in that the upper drum rotates a whole circle
Now cars are generally electronic tachometers, including pointer type and LCD digital display type. There is a digital integrated circuit in the meter, which drives the pointer to move or digital display after calculating the voltage pulse transmitted from the ignition coil. The principle of liquid crystal display speed is similar to the above, indicating that the output is replaced by liquid crystal display.
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