With an odometer, you do not have to guess how much a vehicle has been driven. You can look at the odometer and see exactly how far it has gone since it was first built.
There are ways to check and see if your odometer is working properly. The simplest way would be to use a measuring device to measure the distance of a mile. Then drive your vehicle slowly down the same path and see if the odometer changes by the time you reach the end of the mile. Your odometer can change a few feet before or after the mile marker. This may seem like a small deal, but if you drive 50, miles with the odometer inaccurately measuring, it will add up over time and show you a wrong number.
Digital odometers are now more common than ever. For one, they are cheaper to install than traditional, mechanical ones; this makes them ideal. By going digital, you can also implement plenty of new features into them, such as more trips.
With this technology also comes more advanced tracking systems. Each car manufacturer is different, and technology is always improving. Having a digital odometer opens up the possibility of more accurate tracking, more features, and a better visual experience through the display. Unfortunately, rolling back an odometer is a common practice for dishonest people. Mechanical odometers have historically been easier to roll back. They involve some work to learn how to bypass the security system, but people do roll them back.
People have even discovered how to roll back digital odometers, though it is usually a much harder process because of the more advanced security features. The sad reality is you need to be aware that any vehicle can fall victim to this sort of tampering, so you should always be on the lookout for it. Throughout the years, cars have evolved in terms of design, efficiency, and technology.
However, the odometer operation has not witnessed any significant changes. Cars still employ either of the two approaches to track mileage.
The operation of mechanical odometers starts at the transmission. Here, a small gear used for advancing the odometer is fitted into the transmission system. The speedometer drive cable is then connected to this small gear.
The other end of the cable connects to the instrument cluster. When the engine is turned on, and the car starts moving, the internal transmission gear turns. The connected drive cable conveys this internal transmission gear motion to a set of gears linked to changeable digits. Counting starts at the right side of the set of numbers.
The process [counting] goes on until the amount of distance travelled by the vehicle forces the adjacent digit on the left to roll over. The process repeats itself until all adjacent numbers reach their peak value.
At this point, they all reset to zero and start over again. It is not uncommon for the digits on a mechanical odometer to be slightly out of line. Electronic odometers came after the mechanical ones and are typically digital. As the name suggests, these rely on the vehicle's electronics to establish accurate mileage. Much like mechanical odometers, electronic ones still employ a special gear to change the count reflected on the dashboard. In place of the drive cable, however, a magnetic sensor is used to track the number of gear turns in the transmission.
The signal obtained is then conducted by wires to the on-board car computer which interprets and converts the information into a mileage count. Electronic odometers have the edge over mechanical ones due to their better accuracy. Since they aren't easily manipulated, they generally give an accurate count of the vehicle's mileage. Digital electronic odometers make car buying safe for potential car owners considering second-hand vehicles.
It is worth noting that odometers come with an additional trip meter known as a trip odometer. This trip meter helps car owners determine the mileage of any particular distance without checking the main odometer.
This odometer uses a series of three worm gears to achieve its gear reduction. The input shaft drives the first worm, which drives a gear. Each full revolution of the worm only turns the gear one tooth.
That gear turns another worm, which turns another gear, which turns the last worm and finally the last gear, which is hooked up to the tenth-of-a-mile indicator. Each indicator has a row of pegs sticking out of one side, and a single set of two pegs on the other side. When the set of two pegs comes around to the white plastic gears, one of the teeth falls in between the pegs and turns with the indicator until the pegs pass.
This gear also engages one of the pegs on the next bigger indicator, turning it a tenth of a revolution. You can now see why, when your odometer "rolls over" a large number of digits say from 19, to 20, miles , the "2" at the far left side of the display may not line up perfectly with the rest of the digits. A tiny amount of gear lash in the white helper gears prevents perfect alignment of all the digits. Usually, the display will have to get to 21, miles before the digits line up well again.
You can also see that mechanical odometers like this one are rewindable. When you run the car in reverse, the odometer actually can go backwards -- it's just a gear train. In the movie " Ferris Bueller's Day Off ," in the scene where they have the car up on blocks with the wheels spinning in reverse -- that should've worked! In real life, the odometer would've turned back. Another trick is to hook the odometer's cable up to a drill and run it backwards to rewind the miles. While that does work on older mechanical odometers, it does not work on the new electronic ones, as we will see in the next section If you make a trip to the bike shop, you most likely won't find any cable-driven odometers or speedometers.
Instead, you will find bicycle computers. Bicycles with computers like these have a magnet attached to one of the wheels and a pickup attached to the frame. Once per revolution of the wheel, the magnet passes by the pickup, generating a voltage in the pickup. The computer counts these voltage spikes, or pulses, and uses them to calculate the distance traveled. If you have ever installed one of these bike computers, you know that you have to program them with the circumference of the wheel.
The circumference is the distance traveled when the wheel makes one full revolution. Each time the computer senses a pulse, it adds another wheel circumference to the total distance and updates the digital display.
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