A chronograph is a multi-function sport watch with a stopwatch function. Most have two or three sub-dials or mini dials for measuring minutes and hours. When used in conjunction with specialized scales on the watch dial, it can perform many different functions, such as determining speed or distance. Some chronographs can time more than one event simultaneously.
What do Chronographs do?
The dial at 3 o’clock is the second counter dial. That is the normal seconds operation, which runs separably from the chronograph function.
The dial at 6 o’clock is the 1/10 second counter. This measures seconds 1/10th at a time.
The dial at 9 o’clock is the 30 minute register. This is a timer that resets at 30 minutes.