Have you ever wondered how does a speedometer work? Knowing about the working of something like a speedometer may seem like useless info but it can actually be very helpful.

In this article, you’ll get to know how does your car’s speedometer work and what are the types of a speedometer are there. 

Importance of a speedometer

Most people drive without ever wondering how several components of our cars even work. When was the last time you wondered something like how an oil pressure gauge works. It may seem unimportant but like knowing the causes of high oil pressure or fixing a car horn is important when one of these things get faulty. Similarly knowing a little about speedometers may come in handy sometime.

Brief description of how a speedometer works

A speedometer is one of the instruments in your dashboard used to notify you of how fast or slow you are going. It tells you the speed of your car by calculating the rate of how many times does your wheels turn. It also calculates the size of your wheels. Police officers use radars for the measurement of your car’s speed. These radars use a laser beam that bounces off the car they’re measuring the speed of, then this laser comes back and tells the officer the speed at which you’re going.

Speedometer is the instrument used most often compared to other instruments in your car. Knowing how to check your car’s instruments like a speedometer is important as you have to look at it more than any other instrument on the dashboard.

Types of speedometer

Speedometers don’t have only one type, even if it looks that day. A speedometer has two types. Both types of speedometers perform the same task and look the same way, but they work differently.

The two types are:

  • Electronic speedometers
  • Mechanical speedometers

Electronic speedometer

These types of speedometers are the more rare variants of a speedometer. They’re uncommon, but they have some benefits. Unlike mechanical speedometers that sometimes inaccurately tell you the speed or have a mechanical failure, electronic speedometers are newer and slightly more improved. Electronic speedometers, however, have different benefits and different drawbacks. In newer cars, electronic speedometers are slowly overpowering their mechanical versions.

How does an electronic speedometer work

Electronic speedometers work differently than common mechanical speedometers. In an electronic speedometer, magnets are attached to the rotating drive shaft. These magnets pass by magnetic sensors that measure the rate of their spinning. A small electric current is created when the magnet passes the sensor.

This current allows the sensor to count the time at which the current was recorded. Using mathematics, the sensor converts this frequency to speed. You can see this speed through the electronic LCD fitted in your dashboard. This system can count mileage and speed and then give the data to the odometer. A multimeter helps a lot when checking an electronic speedometer so you should know how to check electrics with a multimeter as it comes useful a lot.

Mechanical speedometer

When you press your gas paddle, gas is supplied to the engine cylinder, and the rate of how much gas is supplied determines the speed at which your wheels spin. You check the speedometer to see this speed. The speedometer shows you the speed in kilometers and miles per hour.

If your wheels aren’t moving or are damaged then check the best car tires for your car so your speedometer can calculate your car’s speed again.

The speedometer calculates the speed of how fast or slow your car’s wheels are going. It shows you this speed either if you’re going forwards or in reverse. If you ever wondered how fast can a car go in reverse then a speedometer will let you know.

 It uses electromagnetism to convert the wheel energy that is generated through spinning to a smooth drifting motion in the gauge. The cable measures the rotation and gives feedback to the speedometer that turns the magnet.

The magnet can easily rotate inside the speed cup that also turns. A wire coil connects the speed cup and the gauge that tells you the speed reading.

Accuracy of a speedometer

No speedometer shows you the perfect rate of speed at which you’re going. If the tires don’t have their exact tire pressure, the measured speed will be a little different from the true speed. As a precautionary measure and because of the law, speedometers need to tell the accurate speed at certain specific speeds. Speedometers are allowed to give 10% greater speeds than the actual speed, so it doesn’t let you know the speeds that are actually slower than the actual speed.

How to read a speedometer

The speedometer is the most commonly used instrument among the instrument cluster placed in your car’s dashboard. It’s most widely used as you frequently look at it every now and then whenever you speed up or slow down.

Every other instrument in the instrument cluster shows you varied things, for example, speed, the temperature of your car, miles traveled, and how much fuel you have. Warning lights are also placed in the instrument cluster. There are even instruments to check engine health such as a diesel tuner.

The speedometer has two different semicircles. Each contains numbers. Smaller semicircles show you speed in kilometers, and the other semicircle shows you in miles. The hand of the semicircle keeps moving around the speed cup, and it stays at the speed you’re currently driving at.


We don’t usually know about most of the things we use in our daily lives. However, even if it doesn’t necessarily come in a situation, we should. Understanding how a speedometer works is helpful if you frequently drive and like cars or want to know more about cars and how their components work.

Knowing types of speedometers is also important as, for example, your current speedometer somehow broke or stopped working, and you went to get a new one. Knowing which type of speedometer to get, how they work, and which is better is super handy in this situation.


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