English 
why you need to recalibrate a speedometer
The driving speed of a car has a great impact on traffic safety. If the error of the speedometer indication is too large, it will be difficult for the driver to control the vehicle normally, and it is easy to cause traffic accidents due to misjudgment. In order to ensure safe driving, the speedometer itself should be accurate and reliable, so that the driver can control the speed of the vehicle according to its instructions. Therefore, it is of great significance for safe driving to detect and calibrate the speedometer and ensure the indication accuracy of the speedometer. Only by correctly understanding the formation of the speedometer error, the measurement principle and the basic structure of the speedometer test bench, can the vehicle speedometer be tested correctly and effectively.
Speedometer error formation and measuring principle: causes of speedometer error.
the speedometer of a car generally transmits the speed of the car to the speedometer through a speed sensor and displays it. Usually, the manufacturing and assembly errors of sensors and speedometers, as well as the decline in performance of the speedometer or tire wear and tire pressure that do not meet the regulations, etc., may cause errors between the speed indicated by the speedometer and the actual speed.
The mechanical speedometer uses magnetoelectric mutual induction to display the speed of the car through the swing of the pointer. In the speedometer, there is a turntable with a pointer shaft, a rotating shaft with a permanent magnet, bearings, hairsprings and other parts. The rotating shaft is driven by a flexible shaft. connect. Due to the natural wear and tear of these parts during use, as well as the magnetic changes of the magnetic components, the indication error of the speedometer will be caused. In addition, the actual driving speed of the car is related to the rolling radius of the wheel. As the mileage of the car increases, the tire wear will gradually increase, making the rolling radius gradually decrease. When the speed of the output shaft of the transmission remains unchanged, the actual driving speed of the car will decrease due to the reduction of the wheel rolling radius. However, since the flexible shaft of the speedometer is connected to the output shaft of the transmission or transfer case, the indicated value of the speedometer will not change with the rolling radius of the wheel, thus causing an error between the indicated value of the speedometer and the actual vehicle speed. In order to eliminate the speedometer indication error caused by the above-mentioned various reasons, it is necessary to regularly detect and calibrate the speedometer.
Get a Quote / Info