About the chronograph

30-minute totalizer

Simultaneously with the start of chronograph measurement, the elapsed time is displayed in 30-minute increments.

Start/Stop button

12-hour timer

Simultaneously with the start of chronograph measurement, the elapsed time is displayed in 12-hour increments.

Reset button

Small seconds

60-second counter. In chronographs, this is often displayed on a sub-dial rather than the center dial.

Tachymeter

A tachymeter is a scale on the dial or bezel that allows for the measurement of speeds such as speed per hour or average speed.
Most of these watches have finely engraved numbers on the bezel or outer edge of the dial, and measurements are taken using the chronograph seconds hand.

For example, if you were to measure the average speed of a car, you would press the start button on the chronograph at the same time the car starts to begin the measurement.
Press the button to stop the needle once you've passed the 1-kilometer mark.
At this time, the number on the tachymeter indicated by the chronograph second hand represents the car's average speed.

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Rolex　Daytona
Panerai Luminor Chrono
Omega Speedmaster

Watch Guide