The traditional speed table is mechanical, typical mechanical odometer to connect a flexible shaft, soft shaft with a steel wire rope, flexible shaft on one at the other end is connected to the transmission gear,
gear rotating drive the steel wire rope, wire rope odometer cover circle a magnet rotates, shield ring with the pointer and through the balance spring put pointer at zero,
The speed at which the magnet rotates causes a change in the size of the magnetic field lines. The balance is thrown out and the needle is pulled.
This kind of speedometer is simple and practical, and is widely used in large and small cars. However, with the development of electronic technology, many car instruments have used electronic speedometer,
a common one is from the speed sensor on the transmission signal, through the pulse frequency changes to deflect the pointer or display a number.