Since the invention of the automobi

Since the invention of the automobile in 1886, the automobile has more than 200 years of development history. The appearance and development of the automobile make the automobile instrument develop and develop continuously. With the rapid development of optical and electronic technology, especially the wide application of computer technology in automobile instrument, automobile instrument is developing towards digital and intelligent direction. The development trend of automobile instrument also shows that the overall development of automobile electronics is also continuous.The usual speedometer has two functions: one is to display the real-time speed of the car through the pointer, the other is to calculate the whole mileage of the car through the mechanical counter. Now cars are turning to the fast direction. Due to the increase of speed, there is a great threat to choose the speedometer driven by flexible shaft. The main reason is that under the condition of high-speed rotation, the flexible shaft is likely to break because of the influence of alternating stress of steel wire. In addition, if the flexible shaft is used too long, it will deform a lot or move with delay. Moreover, for different models, the installation position of the speedometer will also be limited by the length and curvature of the flexible shaft. All of these make the electronic speedometer based on non-contact speed sensor develop rapidly.