We all know how important the odometer is for any car or vehicle because it basically allows you to tell you your car’s total mileage, which is vital for whenever you want to keep your car well-maintained or whenever you want to sell it.
However, if you are wondering how an odometer works, you might be thinking about how it actually measures the mileage of any vehicle.
Does an odometer measure distance or displacement?
An odometer measures distance and not displacement. That’s because an odometer does not have a sense of direction that would allow it to measure the car’s displacement, which is a vector quantity. As such, it is actually measuring the total distance traveled by car and not the car’s total displacement.
For you to understand why an odometer measures distance and not displacement, you have to understand what those terms mean in science or in physics.
Being able to understand some basic terms can make it easier for you to know how an odometer actually works and how accurate it is at measuring your car’s total mileage.
What does a car’s odometer measure?
We all know how important all of those instruments on an instrument cluster are because of how they are able to help you know what the status of the car is.
And when it comes to knowing how banged up or how old your car is, the odometer is the true measure of its age.
In many ways, the odometer is the first thing that plenty of used car buyers tend to look at when they want to know how well the used car is doing.
The reason why the odometer is so important is that it is responsible for tracking your car’s mileage or kilometrage (if you live somewhere that uses the metric system instead of the imperial system).
A car’s mileage is the measure of how many miles the car has been driven, which is the best indicator of how old the car really is.
So, if the car has been driven 50,000 miles even though it is only about three years old, it is older than a five-year-old car that has only been driven 20,000 miles.
That said, if you were to wonder in the scientific sense what the odometer is measuring when it comes to counting the car’s total miles driven, you may be wondering whether it is measuring distance or displacement.
So, for us to understand these different concepts, it is important for us to go back to our basic science or physics to know whether or not odometer’s measure distance or displacement.
When we talk about distance, we are referring to a scalar quantity in the sense that we are measuring how much ground is covered when something is moving. In a sense, what we are looking at here is the distance that a moving object covers from point A to point B.
So, when Little Jimmy walks from his home to his school, which is about three miles away, he is basically covering a three-mile distance.
Meanwhile, when we are talking about displacement, we are referring to a vector quantity, which measures how out of place the object is after it moved. You are basically measuring how much the object changed in terms of its position after moving.
This makes displacement a bit more difficult to explain compared to distance.
Going back to Little Jimmy, let’s say that, from his home, he walked 20 feet east, 10 feet south, 20 feet west, and 10 feet north.
So, if we were to measure the total distance he covered, Little Jimmy walked a distance of 60 feet from point A, which is his home, and point B, which still is basically his home because he only walked in circles to get back to his original position.
However, when we are now looking at Little Jimmy’s displacement, the answer would be zero. That’s because his position never changed during the time that he moved.
By walking 20 feet west and 10 feet north, he basically canceled out the 20 feet east and 10 feet south that he moved as he went back to his original position.
Therefore, considering that displacement is a vector quantity, Little Jimmy was never displaced.
But if we were to say that Little Jimmy moved 10 feet north and stopped right there, then we would say that his total distance covered is 10 feet and his displacement is 10 feet north.
That is basically how distance and displacement are measured.
Going back to what an odometer is measuring, you should know that odometers don’t have the means to measure direction. As such, when you are driving your car, your odometer doesn’t have the capacity to measure a vector quantity such as displacement.
Instead, it is actually measuring the distance driven by your car because of how the odometer is designed to measure a scalar quantity.
As such, if you are one of the few people wondering what an odometer measures, you should know that it measures distance and not displacement because of how it does not have the capacity to measure a vector quantity since odometers do not have a sense of direction.
How does an odometer measure distance?
So, if an odometer measures distance, how does it do so? Well, for you to understand that, you need to learn more about how an odometer works so that you can see how this instrument is smart and crafty enough to know the total distance driven by your car.
Basically, an odometer uses your car’s tires as the basis for how it measures the total distance driven by the car.
What happens is that, in mechanical odometers, there is a cable that connects the input shaft in the instrument panel to an output shaft in the transmission located in your front tires.
So, when the front tires are moving, the cable moves to prompt the gears in the odometer to move as well.
Meanwhile, an electric odometer makes use of a toothed wheel that is connected to the transmission.
As the front tires move, the toothed wheel also moves, and its movements are captured by a magnetic or optical device that records how many rotations the toothed wheel is making.
From there, a signal is sent to the car’s engine control unit, which will now send the value to the odometer so that the distance traveled by the car can be counted.
Of course, the odometer calculates the distance covered by the front tires based on how many rotations they have made and on the diameter of your tires.
As such, stock odometers are usually calibrated depending on the size of your stock tires because that is how they calculate the distance covered by your car based on the rotations that these tires are making.
How would you measure displacement in your car?
As you already know, odometers are made and designed to measure the distance that the car has traveled. So, what about displacement? How can you measure your car’s displacement if the odometer can’t do that?
Well, because displacement is a vector quantity that is based on direction instead of the ground covered when you are moving from one point to another, the only way for you to measure displacement is by using a GPS device that can map out your car’s location and measure its total displacement after moving it.
Some of the more modern cars have GPS devices that are already built-in and have the capacity to calculate the car’s total displacement. However, if you are using an older car, you can probably use a separate GPS device that shows you your displacement after driving.
However, there is also what we call engine displacement, which is totally different from the type of displacement we are talking about because it is a totally different kind of measure altogether.
But engine displacement is also one of the important measures of how well a car performs as most companies tend to show engine displacement when they are marketing their cars.
Engine displacement, according to yourmechanic.com, is the swept volume of pistons inside the cylinders.
This is calculated from the number of cylinders, stroke, and the diameter of the cylinders themselves. And the reason why engine displacement is important is that it is the basis for the car’s power and for fuel efficiency as well.
So, if you wanted to calculate engine displacement, refer to this formula:
Displacement = stroke length x π x ( ½ x bore)2 x number of cylinders
What’s the car’s most common engine displacement?
In most of the cars we see today, we often see them with an engine displacement of half a liter or 500cc. We got this number from the fact that most of the modern cars in the market today run on 2-liter engines with four cylinders.
From there, we get a half-liter engine displacement, which is expressed in cubic centimeters or cc, which is 500.