All cars have an odometer. Every car enthusiast knows what it is. However, not everyone knows the structure of this device, the principle of operation, malfunctions and repair methods. In addition, modern cars are equipped with electronic equipment that is difficult to understand. Let's look at everything related to odometers.
Purpose and device
What is this device? This is a special mechanism that is designed to measure the number of revolutions of a car's wheels while driving. In other words, this element allows you to measure the distance traveled by the machine. The odometer readings are displayed on the vehicle's dashboard. The device shows the driver the daily and total mileage. Both of these scales are located directly on the speedometer block.
So, the purpose of the odometer is clear. Now we need to move on to the design of the mechanism. This device consists of a counter, which is designed to count the number of revolutions of a car wheel. The device also has a special controller. It is directly connected to the counter and is necessary to record revolutions. Finally, there is an indicator. The element is located on the speedometer and directly shows the driver the kilometers traveled.
Operating principle
Now we should move on to how the odometer works. What it is is already more or less clear. The operating principle of this measuring device greatly depends on the type of device. This can be an electronic odometer or a mechanical one. So, a car wheel makes a certain number of revolutions during each kilometer. Moreover, this indicator is always the same regardless of the speed of the vehicle. If you know exactly how many revolutions the wheel has made, then you can easily calculate the distance traveled in kilometers (or miles for American cars), which is shown on the meter. The oldest mechanical measuring instruments operate using a flexible cable. The latter rotates at the same speed as the wheel. This rotation is transmitted from the gearbox output shaft. The cable transfers force to a drum counter installed in the dashboard of the car. The device has five reels with numbers.
They are connected to each other by a worm gear. The cable itself is connected to the first drum through a gearbox. Mechanical devices are good because repairing an odometer of this type is simple and will require replacing worn parts.
How is it useful?
It would seem how this small device that counts kilometers can be useful for a car owner. But in fact, the role of the odometer in the life of a motorist is quite large. This is an important tool, using the readings of which they determine the time of car maintenance, oil change, valve adjustment, timing belt replacement, wheel alignment check and other operations.
The device best indicates the condition of the car. It’s not just that experienced car enthusiasts, when purchasing a car second-hand, are interested in the mileage. Based on this, some unscrupulous sellers have learned to reduce the number of kilometers traveled. Therefore, when buying a car on the secondary market, it would be useful to conduct a short test drive. It is necessary to watch the speedometer needle while driving. If the odometer moves jerkily, with jams, or the speedometer needle does not move smoothly, then the mileage has been changed. Before the sale, the seller twisted the odometer. Sellers know very well what it is, so it’s almost impossible to find honest mileages on the secondary market.
How to use the daily counter?
Using this device, the driver can accurately determine the vehicle's fuel consumption. Sometimes it may seem that the engine is consuming too much. In this case, you should not immediately go to a service station and do diagnostics. First you need to accurately determine fuel consumption. They put a canister of gasoline in the trunk, wait until all the fuel in the tank is empty, then reset the daily counter to zero, pour gasoline from the canister and drive the car as usual until the tank is empty again. Then all that remains is to divide the number of liters by the total mileage of the daily meter, and multiply the resulting result by 100.
In this simple way you can get an accurate figure for fuel consumption. Knowing information about how much fuel the car “eats”, you can accurately calculate how long the gasoline poured into the tank will last. Experienced motorists recommend resetting the daily counter after each refueling. You can also determine mileage over a certain time or distance between different places on the route.
Designs of different types of odometers
This element is a dial. But this is only part of the device. There is a gear on the secondary shaft of the gearbox, which meshes with the meter drive gear. This part is connected by a flexible cable to the block, which is responsible for the speedometer-odometer. Mechanical devices are among the oldest. You can check the mileage on these using any devices that can rotate. The counter counts revolutions, which means that with the help of any electric motor you can both twist and turn the numbers on the counter. Electromechanical counters are systems based on the same gear on the secondary shaft of a gearbox (it doesn’t matter whether it’s an automatic or manual transmission).
But it already activates an electromechanical sensor. The sensor generates electrical impulses that, through wires, enter the speedometer unit, where, according to the frequency of their arrival, a small electric motor spins - the odometer drive. Most cars, including modern ones, are equipped with this device. The odometer is adjusted here using CAN devices. Electronic odometers differ from electromechanical ones in that they are completely electronic sensors and LCD indicators. They are widely used on cars and trucks. Their distribution is due to the fact that adjusting the odometer of such a plan will be difficult. However, now this is not a particular problem. Correction is carried out using special devices.
Types of odometer sensors
Pulse sensors based on the Hall effect are used.
Induction-type devices that operate on the principle of electromagnetic induction are also used. In mechanical elements, combined systems are used. This is a gear sensor, which is connected to the secondary shaft of the gearbox, and a pulse sensor.
Odometer and errors
Almost all measuring instruments have errors. Odometers are no exception. Now there is a certain standard for errors. For mechanical equipment it is no more than five percent. If the car is used in harsh conditions, then the error level increases to 15 percent. Severe conditions include slipping. The car seems to be moving, because the wheels are rotating, but it itself remains in place. In addition, the level of error is greatly influenced by gaps, weakened springs in the structure, weak cable, and poor grip. The VAZ electromechanical odometer readings are read from the speed controller. In this case, the error will be very low. It is worth noting the high reliability of the devices. Such devices rarely produce a figure whose error is higher than 5%. The electronic odometer is one of the most accurate.
The design does not provide for any mechanical connections between the components. However, there is an error here too. It is often associated with wheel wear or replacement.
Summary
So, we found out how the odometer works, what it is and what types it is. This is a necessary thing in a car. You can do a lot with it. The odometer allows you to accurately determine when to change the oil and will also help you determine your fuel consumption.
Probably many people like to keep track of the mileage of their iron horse - how many kilometers there, how many there. Also, after a certain mileage, we need to carry out the necessary maintenance - for example, changing the oil, timing belt, etc. All this is monitored by a simple, but very “smart” device - an odometer. The name is unfamiliar, many have probably heard it, but don’t know what it is. I’ll try to explain, as usual, simply and in layman’s terms...
First, as usual, let's start with a definition.
Odometer - This is a device that records the mileage (kilometers) of a car. The principle is simple, it counts the number of wheel revolutions and thus displays the distance traveled, which is displayed in kilometers for Russian and many European cars, and in miles for many American cars.
As you can see, this is simply a display of mileage on the speedometers. Previously, the device was mechanical, now it is increasingly electronic or hybrid (electronics + mechanics).
How does it work?
It is important to understand how this unit works and what parts it consists of. If you don’t go into the wilds, the device can be roughly broken down into three components:
1) This is a sensor that is installed next to the wheel (there are options almost in the wheel itself), there are also options that are installed in the transmission (gearbox) - they take into account the speed in a certain way.
2) A counter or drive that counts these revolutions, then transmits them to the head unit
3) Display is a speedometer (for simple mechanical types), or an ECU that receives data and then displays it on a digital display.
I would like to note that now there are practically no mechanical odometers left, everything is moving to digital.
Device types
I propose to dwell in more detail on the types of odometer devices, so to speak, to go through history.
1) Mechanical odometers - the simplest and most easily corrected.
Typically, a sensor was hung on the gearbox, which mechanically, through a cable, transmitted information to a special unit, which in turn displayed the information on the speedometer monitor. To be honest, the reliability and reliability of the data was at a low level. Craftsmen could crawl under the car, unscrew the cable from the gearbox, and the mileage was simply not taken into account. It was also easy to remove the speedometer itself, in which the odometer was located at the bottom, and twist it by hand. So the mileage was easily adjusted in the right direction.
2) Hybrid odometers — The first electronic control units and electronic displays are already appearing here.
The design remains mechanical at the level of the drive and transmission, that is, information is obtained mechanically, after which it is converted into electronic impulses that are converted into kilometers on the odometer.
3) Electronic or digital odometers - This is a completely electronic system, starting from collecting data from drives or wheels, ending with processing (often it) to displaying it.
Such systems are the most resistant to mileage twisting; they are not so easy to adjust, because electronics are everywhere. But folk craftsmen have learned to correct them too. Usually this is the ECU firmware.
The electronic version records not only the total mileage of the car, but also the daily mileage, which is very convenient. Let’s say with a daily mileage, you can measure the distance to a particular point, and then calculate the gasoline consumption. The odometer in a car is one of the indicators of condition. Yes, yes, you heard right exactly the state. This is because the greater the mileage (kilometers) of the car that this device recorded, the more worn out the car is and must be serviced. You need to go to the station to change parts of the mechanisms, because according to the regulations, many parts of the car are changed precisely for this indication. For example, transmission oils, timing belts or chains, etc.
Reading accuracy
The odometer cannot be called an ultra-precise device; its error is significant, even with digital ones it can be 2 - 10% of the total mileage. There is nothing wrong with this - after all, the odometer does not count in millimeters and centimeters, but in tens or even hundreds of meters and kilometers. I would also like to note that the error may increase depending on the wear and tear of the car.
If we decompose the error into groups of odometers, it becomes clear:
Mechanical have the highest degree, because they have mechanical parts in each of the drive links. Even new ones have an error of 3 - 5%, but already worn ones have an indicator of about 10%.
Hybrid Due to their digital component, they cut off a large number of errors; they count pulses, and therefore the error, even with high wear, rarely goes beyond 5%.
Digital They are practically devoid of any shortcomings, they have no mechanical parts, and therefore they always take into account relatively even readings, the error even with long runs is no more than 2%.
But it’s worth noting that when a car slips, say on ice or snow, the wheel spins, a record is kept, but the car essentially stands still! So much for the error, even for electronic versions.
Twisting - odometer adjustment
First, I’ll answer why it is being corrected! Everything is very simple, the higher the mileage, the higher the wear and tear of the car as a whole, as well as important components, engine, transmission, suspension - a lot of “sores” come out. For example, many German cars will require serious financial investments after 90 - 100,000 kilometers, at least to replace the turbine and repair the robotic transmission (if we say).
Therefore, many dishonest sellers, especially resellers (persons who buy and sell cars), correct odometer readings. If it is mechanical, then everything is simple, it is simply reeled back using mechanical action. But if the odometer is electronic, then it is much more difficult to correct it, because there are no mechanical parts in it. We need special devices that can connect to the car's microcircuits. Therefore, cars with electronic odometers are more protected from adjustments. Although folk craftsmen reel them in too. Sometimes it is very difficult to understand the actual mileage, especially if the tires are new, the body is polished, the interior has been dry cleaned, etc. They may tell you that the mileage is only 20,000 km, but in fact it may already be over 120,000 km. So you need to be careful when buying a used car. Turn to professionals, even if you give him a couple of thousand rubles, but he will save you a lot of money on subsequent repairs.
This word comes from the Greek: ὁδός - road and μέτρον - measure. In a car, this is a meter that records the distance traveled by it. Each car usually has a full mileage odometer - without the ability to reset the readings - and a daily recorder, the readings of which can be reset to zero. The odometer is structurally combined with the speedometer and has one drive with it.
Role in the life of a car
The odometer is a very important tool, since its readings determine the time for vehicle maintenance (changing engine oil, adjusting valves, replacing the timing belt, checking wheel alignment, etc.). And therefore, it indirectly indicates the technical condition of your car. It is not without reason that experienced car enthusiasts are interested in the mileage of a car when buying a used car, and even more experienced sellers of such cars have long learned to reduce readings in various ways. But not everyone wields them equally masterfully. Therefore, when buying a used car, it would be a good idea to ask the seller to take you for a short drive in it and observe the behavior of the speedometer needle and the smoothness of changes in the odometer reading. If you notice jams or jerks in their operation, rest assured that the odometer shows the value that the car owner considered appropriate for this case.
Using a daily plan
I hope we found out what an odometer is and how it is used. Now, a few examples of how you can use the daily mileage counter:
This is the first use that comes to mind for the daily odometer.
The dashboard of a modern car, of course, cannot be compared with the dashboard of an airplane, however, it can confuse an inexperienced driver. The speedometer, tachometer, odometer and other instruments and indicators, while certainly necessary and important, still require an explanation of their functions and their purpose. In this article we will talk about what a car odometer is, what they are, and also say a few words about how and why the readings of these devices are distorted.
Electronic odometer on the dashboard. Below is the total mileage, at the top is the daily mileage, on the right is a button to reset the daily mileage.
If the speedometer measures the speed at which the car is currently moving, then the odometer shows the number of kilometers the car has traveled. Translated from Greek, odo means road, and meter means to measure. So in the end we get a kind of “road meter”.
The odometer counts the kilometers traveled by counting the number of wheel rotations. Typically this device has two types of readings. The total mileage of the car, here we count every kilometer traveled by the car from the moment it left the assembly line, as well as the so-called daily mileage. It is called a daily allowance rather arbitrarily. In essence, you press a button, reset the readings of this scale, after which you can see the mileage of any segment of the route that you have covered over a period of time. Well, this figure is usually called the daily rate by taxi drivers, which is where the name comes from.
How does an odometer work on a car?
What does a mechanical odometer look like on the dashboard?
There are only three types of odometers:
- mechanical;
- electronic-mechanical;
- electronic;
Mechanical odometers are more than simple. There is a cable that connects to the output shaft of the gearbox, there is a mechanical counter with several, usually five, drums, to which the rotation of the cable is transmitted through a special mechanism. The reels are marked with numbers from which the odometer readings are compiled.
In electronic-mechanical odometers, the rotation of the cable is recorded using an electronic counter. Well, in purely electronic odometers there is no cable at all. Instead, Hall sensors or other electronic components are used to calculate the distance. Moreover, in the case of an electronic odometer, the readings are recorded by the on-board computer of the car. Such systems are considered the most accurate and reliable, but even they allow a measurement error of as much as five percent.
What does an electronic odometer look like on the dashboard?
The reasons for the distortion of odometer readings may be different. For example, this is wheels slipping when they rotate, but the car stands still. And although such moments make up a tiny part of the overall performance of the car, with high mileage values, they can contribute to distortion of the odometer readings.
Another reason for inaccuracies in the readings of such devices is tires with a radius different from that for which the odometer is designed.
Well, perhaps the most important reason for distortions in car mileage indicators may be, we’ll talk about them.
Video on checking odometer readings
Why and how to rewind odometers
The reasons for conscious corrections of the odometer readings may be:
- desire to reduce the actual mileage of the car;
- attempts to hide improper use of the machine;
- elimination of some difficulties with documenting the official vehicle fleet;
As we can see, the reasons are mostly not very correct and decent. If you reduce the actual mileage figure, the car can be sold at a higher price. If you roll back the odometer to certain values, you can hide the fact that the car has been driven, and sometimes driven a lot, when it should be sitting quietly in the garage.
However, today equipment is officially being produced that allows you to adjust the indicators even for electronic odometers, which without special skills and knowledge is a very difficult task. Moreover, in a number of European countries, such manipulations are punishable by a prison sentence, which is quite significant for such tricks.
The easiest way, from a technical point of view, is to rewind the mechanical odometer. The cable is removed from the shaft, attached to a drill or other similar power tool, after which it rotates for some time in the desired direction. But not all even mechanical odometers allow you to rewind yourself so easily. Then you have to remove the counter itself and perform more complex manipulations with it.
As for electronic odometers, of which the majority are today, they are rewound using special devices and software that enter the changed data into the memory of the car’s on-board computer. In some cases, it is necessary to reprogram one or more on-board controllers, because the readings of the magnetic wheel speed sensors are transmitted not only to the odometer.
It should be noted that altered odometer readings not only mislead either the potential buyer or the person monitoring the use of the car, they can be an obstacle to the timely completion of the car, maintenance, or even the correct diagnosis of certain problems. Therefore, in the vast majority of cases, such corrections are essentially fraud.
Speedometer... Every motorist certainly knows about this device. However, not everyone can answer what an odometer is in a car, and this is quite natural, because this device is far from being as simple and primitive as it seems at first glance.
At the same time, not everyone sees the difference between an odometer and a speedometer - a completely different device combined with it. Well, we will try to clearly explain the differences, as well as what it is - a car odometer.
Operating principle of the odometer
In scientific terms, an odometer is a mechanical or electronic device that determines the number of revolutions made by a wheel, that is, a counter. Thanks to this information, the car owner can determine the path traveled by the car during its entire service life or over a certain period of time. That is, the information received by the device is communicated to the driver in numerical form, and specifically, the kilometers traveled.
The principle of operation of the device is as follows: for one kilometer traveled by a car, the wheel makes the same number of revolutions. Knowing how many revolutions it has made in total during a particular path, it is easy to calculate the kilometers traveled, and this is what is displayed on the odometer.
In addition, by resetting the odometer data before driving, you can easily set the distance from point A to point B or calculate how much the car traveled on one fuel fill. Probably any driver knows about all these functions of the odometer.
Their types
Despite the fact that the car is an invention of the relatively recent past, such a device as the odometer has been known for a very long time - its inventor was Heron of Alexandria. It is quite logical that the first mechanism of this kind was mechanical.
Actually, in the automotive industry, all odometers originally used were of a purely mechanical design, and the counter itself, located on the dashboard, was a set of drums with printed numbers that changed as the car traveled a certain distance (one kilometer or mile).
Such odometers were distinguished by their simplicity of design and reliability, but they also had several significant drawbacks. The main one was the limitation of the mechanical counter - when a certain mileage was reached, it was reset to zero.
In addition, the accuracy of such an odometer was achieved only when using wheels of a strictly defined size on a vehicle, and deviation from it caused a serious error in measurements.
In the mid-twentieth century, automakers began using electromechanical meters, which, receiving information from a mechanical sensor, displayed information not using archaic drums with numbers, but on a liquid crystal display.
Later, fully electronic odometers were created that received information about wheel speed from the so-called Hall sensor. At the same time, the information received from it was processed by the car’s on-board computer and stored in its memory, which made it possible to save information not only about the total mileage, but also about individual trips.
This was very convenient, for example, for measuring fuel consumption or distance traveled on several trips.
Odometer and speedometer: what's the difference?
As we have already said, not everyone knows about the difference between two completely different devices - the odometer and the speedometer. Many are misled by the fact that the odometer scale on almost all cars is integrated into the speedometer scale.
It is logical that some quite reasonably assume that this is the same device. In fact, the difference between the devices is very significant.
The speedometer is used to measure the speed of the vehicle and is in no way connected with the functions of the odometer - a counter for the mileage traveled by the vehicle.
The combination of the scales of these instruments is due only to the convenience of human perception of information, as well as tradition. However, today the odometer readings are displayed on the on-board computer display among the main information, and this display is again located in the area of the speedometer scale. However, these devices cannot be confused in any way.
Using the odometer to determine the mileage of a used car
It is well known that the odometer is the main means by which the mileage of a vehicle can be determined. This criterion is one of the most important, since the mileage traveled allows us to assess the general technical condition of the car, the degree of wear of components and assemblies, as well as the remaining engine life.
It goes without saying that many car enthusiasts who part with their own vehicle often have a desire to change the odometer readings in order to increase the initial cost of the car being sold.
We will leave aside the moral and ethical side of this issue and look at how technically realistic it is to “twist” the odometer counter.
Here we should once again delve into the history of this device. The first, mechanical, odometers had a serious drawback - it was very easy to change their readings. In fact, this reason forced automakers to look for various ways to protect data, which ultimately led to the creation of electronic devices.
In them, as we have already written, information about the total mileage is “hardwired” into the car’s on-board computer, and it is much more difficult to correct it. In practice, it is still possible to set the electronic odometer to negative, but this is done not by interfering with the operation of mechanical components, but by rewriting the information stored in it in the memory of the on-board computer.
Video about twisted runs on cars:
Today on the Internet there are many offers in this area, which is worth at least the well-known website odometr.rf, reviews of which speak about the relative simplicity of this procedure.
But do not forget that in most modern cars, information about mileage is stored in several electronic units independent of each other, and is quite capable of revealing the fact that the odometer readings are “twisted” on the part of the car enthusiast.
conclusions
As we can see, getting an answer to the question of what an odometer is is not so difficult. Knowing the operating principles of this motorist assistant, you can easily receive information about the distance traveled, find out the total mileage of the car, and control fuel consumption. Of course, this is one of the most significant devices in any vehicle.
Video - is it possible to find out if the mileage is incorrect (odometer readings) - tips for repurchasing.
