In literal terms, "tachometer" means speedometer.
A tachometer is a series of numbers that usually start from 400 next to the number 2 and end at 60 next to the number 12, marked on the dial of a wristwatch.
This system is designed to measure speed within a range of one kilometer. These numbers indicate the speed of an object moving within this range. A chronometer stopwatch is used to display this speed, and fractions of a second can also be calculated. The important thing is how it is used, and you can act according to your own taste and preference. Here, we will describe how to use the tachymeter in two different models.
1 - To measure speed based on the exact distance (1 kilometer):
First, mark two points at a distance of one kilometer from each other. Measure the time it takes for the object of interest to enter and exit the measured distance (using a chronograph wristwatch). Your chronometer's hand should align with one of the numbers on the tachymeter scale, displaying the average speed of the object.
Note: The speed range displayed on these watches is between 60 kilometers per hour to 400 kilometers per hour.
For example, if you are traveling on an intercity bus on a highway where each kilometer is marked with a sign, you can activate your chronograph as soon as you pass the first sign and stop it when you pass the next sign. The chronograph hand (the seconds hand) will display the average speed of the bus to you.
2 - To measure distance at a constant speed (1 kilometer):
An object is moving at a constant speed (e.g., 120 kilometers). When a chronometer starts moving, after reaching the desired speed value (30 seconds), the object has traveled one kilometer.