A chronograph is another name for a watch with a stopwatch function. The buttons, or pushers, on a chronograph start, stop and reset the stopwatch. The watch tells time as usual, even while using the chronograph.
- Start the timing
Press the top button on the right side of the watch to start the timer. When the timer starts, the longer second hand starts to move. For every complete rotation the hand makes around the dial, an increment of time is recorded in a subregister, or recorder, on the watch. The subregister displays the recorded time in seconds, minutes and possibly hours.
- Stop the timing
Press the top button a second time to stop the timer. The total time elapsed is displayed in the subregister. The amount of time recorded depends upon the capabilities of the watch. A chronograph can record anywhere from 30 minutes to 12 hours.
- Reset the stopwatch
Press the bottom button to clear the stopwatch, which resets the subdial and the longer second hand.
- Use the tachymeter
Some chronographs also feature a tachymeter, which allows the wearer to calculate speed based on the time recorded and/or distance traveled based on the speed. The tachymeter is the scale of numbers featured on the outside of the watch. The standard scale converts between the duration of the event in seconds and the number of times the event occurs in an hour. To calculate the speed, travel a known distance, and use the stopwatch function. Divide the 3,600 seconds in an hour by the number of seconds recorded by the stopwatch. To calculate distance, hold your speed constant. When the second hand reaches the mark on the scale equal to the speed, the distance traveled is equal to 1 mile.