what is it in the car? What does it show and how is it different from a speedometer?

The driver constantly while driving a car sees a dashboard in front of him, on which various measuring devices are placed. So, the speedometer displays the current speed, the tachometer shows how many revolutions per minute the crankshaft makes. There are also indicators of oil pressure, battery charge, antifreeze temperature. Trucks and passenger vehicles have gauges that show brake pressure, tire pressure, and transmission oil temperature gauges.

There is also another instrument, usually located between the tachometer and speedometer, which shows the mileage traveled by the car. This device is called an odometer - a very useful thing. In particular, if you buy a used car, you need to check if the mileage is twisted. How to do this - we told earlier on Vodi.su in one of the previous articles.

Principle of operation

Knowing the radius of the wheel and the speed of the car, you can use a simple formula to determine the angular velocity with which an arbitrarily chosen point on a circle moves around the center. Well, using all these data, you can easily determine which path the car, cart or chariot traveled.

Indeed, the idea of ​​creating this simple device came to the mind of the Greek mathematician Heron of Alexandria, who lived in the first century of our era. According to other sources, the first person who was enlightened by the idea of ​​​​the odometer was either the well-known Archimedes, or the Chinese philosopher and thinker Zhang Heng. In any case, it is reliably known that already in the III Art. n. e. the Chinese actively used this invention to measure the distance traveled. And they called it "the counter of the path that the cart passed."

Today, this device is installed on any car and motorcycle. It works on a simple principle: the counter is connected through a sensor to the wheel. The sensor determines the angular velocity of rotation, and the distance traveled is calculated in the CPU.

The odometer can be:

• mechanical - the simplest option;
• electromechanical;
• electronic.

If you have a more or less modern car, then most likely it is equipped with an electronic odometer, which measures the distance traveled due to the Hall effect. We also wrote earlier on Vodi.su about the Hall sensor, which directly measures the speed of rotation of the crankshaft. The data obtained is absolutely accurate, and the measurement error is minimal, not exceeding 2 percent (for electronic) and five percent (for mechanical and electromechanical devices).

What you need to know about odometers?

The advantages of electronic odometers over less advanced types is that the electronic odometer does not reset to zero. In a mechanical indicator, the wheels make a full circle and reset to zero. As a rule, the mileage is more than 999 thousand km. they are not displayed. In principle, few vehicles, other than trucks or passenger buses, are capable of covering such a distance throughout their entire operation.

You also need to pay attention that the odometer displays both the total mileage and the distance traveled in a certain period of time. This applies to both electronic and mechanical odometers. Usually the indicator is located directly on the dial of the speedometer. Therefore, it is probably often thought that the speedometer and odometer are one and the same instrument. The upper window shows the total mileage, the lower window shows the distance traveled per day. These readings can be easily reset.

When buying used cars, drivers first check the mileage that the odometer shows. There are a number of signs by which you can guess that the mileage was twisted on a mechanical odometer. In principle, would-be masters have learned how to twist electronic devices. But you need to understand that in modern cars, all data on the state of the vehicle is stored in the computer's memory, which is almost impossible to clear. That is why, if any suspicions arise, you must either refuse to buy, or drive the car for a full diagnosis and find out its real mileage.

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