Many car owners will encounter the following situations more or less in their daily driving: First, they are caught speeding during a certain speed limit period, and no illegal information is found after that; But the cars on both sides were driving faster than me. So there is a question, is there an error between the instrument panel speed and the radar speed measurement?

Before answering this question, someone did an experiment: let two different cars test the speed of the cruising speed of 60 km/h and 80 km/h under the same road conditions through the radar speed measurement. It was found that no matter driving at 60 km/h or 80 km/h at medium and high speed, the actual speed is higher than the radar speed measurement, and there is a clear gap. So, where does this error come from? Which speed is the most accurate?

First, let's understand the principle of vehicle speed measurement. Normally, each wheel has a corresponding sensor to detect the number of turns of the wheel, and then calculate the actual speed. But this speed is not faithfully reflected on the instrument panel. There are two reasons. First, the state clearly stipulates that the speed indicated by the speedometer must not be lower than the actual speed, which means that the error is actual and allowed by the state.

According to the specified relationship between the indicated speed and the actual speed (0≤indicated speed-actual speed≤actual speed/10+4km/h), assuming the actual speed of the vehicle is 80km/h, the indicated speed should be 80km/h Between ~ 94 km / h are in line with the standard.

Secondly, in addition to the above-mentioned reasons for setting the vehicle itself, the circumference of the tire will be affected by many factors, and the effective radius of the tire is precisely the effective parameter for the vehicle to calculate the real-time speed.

So, some people will ask, is the speed measured by GPS accurate?

The test is also carried out with two vehicles. The two vehicles are driven at a cruising speed of 60 km/h and 80 km/h respectively, and the actual vehicle speed and the navigation display speed are recorded. The results show that the navigation speed measurement is the closest to the actual speed of the vehicle.

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