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does a speedometer measure speed or velocity speed
What the speedometer measures is the instantaneous speed of the vehicle in the detection area, which has nothing to do with the speed value on your speedometer. Moreover, the speed value on the speedometer is higher than the actual speed of the vehicle. According to the regulations, the value measured by the radar must not be higher than the actual speed of the vehicle. Therefore, what the speedometer measures is the actual speed of the vehicle, and it is the instantaneous speed value, not the average speed.
I believe that most driving friends will understand the inconsistency between the displayed speed of the instrument panel speedometer and the actual speed, but even old drivers do not know the secret. Therefore, the following situations are often encountered: when driving past the speed measuring point, the speedometer shows that the vehicle speed has exceeded the limit speed, but there is no overspeed record after query. To judge the accurate vehicle speed, you can: Method 1: with the help of GPS equipment, the on-board GPS uses location mobile speed measurement, and transmits and displays it every minute as a node. The vehicle speed measured by GPS is close to the actual vehicle speed. If you drive at a constant speed for a period of time on a flat road, you can roughly judge the actual vehicle speed by the speed recorded by GPS. Method 2: with the help of average vehicle speed calculation, the instrument panel in the vehicle displays the average vehicle speed, which is the actual vehicle speed, because the fuel consumption of the vehicle needs to be calculated through the average vehicle speed. Keep driving at a constant speed for a while, and you can know the difference between the dial data and the real speed through the average speed displayed on the driving computer.
The vehicle speed is calculated by calculating the number of rotations of the drive shaft, and the calculation result will be sent to the CAN bus and finally reflected on the vehicle instrument; However, there will be some errors in the data captured by the sensor, so it is impossible to accurately calculate the actual speed! Secondly, at the level of rules, there are also requirements for apparent speed, so it will inevitably lead to inaccurate apparent speed of cars.
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