Tachometer, also known as tachymeter, literally means speedometer.
Tachometers are numbers engraved on the watch bezel that usually start at 400 next to the number 2 and end at 60 next to the number 12.
This system is designed to measure speed in the range of one kilometer. These numbers indicate the speed of an object moving in this range. A stopwatch shows the pace, but the fraction of a second can also be calculated and only how it is used matters. You can act according to your taste and vision. Here we describe how to use a tachometer in two different ways.
1 - To measure the speed according to the accurate distance (1 Km):
First, mark two points at a distance of one kilometer from each other and measure the time of entry and exiting of the desired object (by the watch chronograph). Your chronometer hand is placed on each of the tachometer numbers.
Note: The displayer shows the speed within the range of 60 to 400 Km in these watches.
For instance, You are travelling on an intercity bus on one of the highways, where the separating signs for each kilometer are marked. So you can activate your chronometer as soon as it passes the first panel and stop it until it passes the next board. The chronograph hand shows the average speed of the bus.
2 - To measure the distance at a constant speed
A subject is moving at a constant pace (for example, 20 Km). Whenever the chronometer starts moving and reaches the desired speed, it has travelled 1 Km.