How is the mileage calculated?
2 Answers
The principle is actually quite simple: it involves multiplying the tire's rotation count by its circumference. Since the tire's circumference is fixed, knowing the wheel's rotation count allows calculation of the vehicle's mileage and speed. For example, if a tire has a circumference of 1 meter and rotates 1000 times per minute, the car would travel 1000 meters per minute, or 36 kilometers per hour. The main difference between various types of odometers lies in how they obtain the wheel rotation signal. Most vehicles use electronic odometers. The dashboard essentially functions as a display screen, with parameters controlled by the vehicle's computer. The speed sensor transmits the wheel rotation signal to the computer, which calculates a value based on pre-stored programs and displays it on the dashboard, continuously updating as the car moves. There are two methods for the speed sensor to obtain signals: one is from the transmission output shaft, and the other utilizes the ABS wheel speed sensor's signal. Most vehicle dashboards display two types of mileage: one is the total mileage the car has traveled, and the other is a measurable mileage that can be manually reset by the car owner. Next to most digital displays, there's a small button (cylindrical in shape) that can be held down to reset the measurable mileage.
The calculation of a car's mileage is actually quite straightforward. There's a speed sensor on the wheel connected to the transmission. Each time the wheel rotates a certain number of times, it sends an electrical signal to the odometer to accumulate the count. For example, one rotation might correspond to about 0.5 meters, and the system converts this into kilometers using a fixed ratio, displaying it on the dashboard. Modern cars also use CAN bus technology to ensure data accuracy. If the sensor wears out or becomes loose, the readings may drift, requiring timely repairs. Mileage not only reflects the vehicle's usage but also serves as a benchmark for maintenance, such as changing the engine oil every 5,000 kilometers. It's recommended that car owners develop the habit of checking the actual mileage using the OBD interface or an app, as preventing tampering is especially important since accurate data ensures driving safety.
