What are the speedometer and odometer?

[SanJohn]

Speedometer: A device that measures and displays the speed of a vehicle. Odometer: A device used to determine whether a car should be scrapped based on the distance it has traveled. Here is some additional information: 1. Speedometer: The speedometer is commonly known as the vehicle speed and mileage meter. It comes in two types: roller counter and dot-matrix LCD screen. It consists of a speed gauge that indicates the vehicle's speed and an odometer that records the distance traveled. 2. Working Principle: The purely mechanical odometer consists of a worm gear mechanism and a number wheel. When the car is in motion, the odometer drive gear (worm gear) installed on the gearbox main shaft drives the odometer driven gear (worm) to rotate. The worm drives a flexible shaft, which then rotates the counter on the instrument panel through the worm gear mechanism, displaying the mileage.

[DiErin]

Don't confuse the speedometer with the odometer. The speedometer in a car is a round dial, pulsating like a heart right behind the steering wheel. When driving, the needle swings—60, 80, 100—showing our speed in kilometers per hour. What veteran drivers often call '100 mph' is actually incorrect; 100 mph equals over 160 kilometers per hour. As for the odometer, it usually has two small windows: the top one shows the total mileage, recording how far the car has traveled since it was born, and the bottom one is a trip meter that can be reset for short trips. Nowadays, many new cars use LCD screens, but the functions remain the same. Every maintenance check relies on reading this meter.

[LeDominic]

When repairing cars, I often encounter beginners asking about the difference between these two dials. Simply put, the speedometer manages instantaneous safety using electromagnetic induction principle—tire rotation drives a flexible shaft, which converts into a magnetic field to move the needle. A vehicle speed sensor hidden in the instrument panel ensures accuracy. The odometer records cumulative distance, relying on electronic sensors and the vehicle's computer to count, linked to gear rotation. If the speedometer fluctuates erratically, it's likely due to a dirty wheel speed sensor; if the odometer stops working, it's probably because the instrument cluster connector is damp. Although these two are adjacent, their functions are completely independent.

[AdelynLynn]

Just explained this to my wife last week while teaching her to drive. You see, the digital dial in the middle of the dashboard is the odometer, recording the total kilometers we've driven since buying the car. The round dial with markings next to it is the real-time speedometer - step on the gas and the needle shoots up. Important point repeated three times: 60 km/h is NOT 60 mph! A true 60 mph is close to 100 km/h. On highways I watch the speedometer, while in city traffic I check the odometer to calculate fuel consumption. Some cars even have a hidden third gauge - the trip meter. Pressing its button resets the count, super useful for road trips.