June 12, 2020 3:02 PM
The chronograph is one of watchmaking's most recognized complications, but it is often misunderstood. With several hands whizzing around the main dial and a collection of sub-dials (normally two or three) it can be easy to get confused. Additionally, it is not uncommon for the bezel to be printed with a complicated numerical scale, which can further bamboozle a first-time user.
Simply put, a chronograph is able to measure elapsed time on demand. It is effectively a stopwatch function on top of your normal watch (a stopwatch performs the same function as a chronograph but can not tell the time as well).
The most common chronograph set-up features centrally-mounted hour and minute hands and a small seconds hand in one of the sub-dials (often at 9 o'clock in a 3/6/9 sub-dial layout) for telling the time. The large, centrally-mounted seconds hand is part of the chronograph function along with the other two sub-dials, which normally record minutes (often either 30 or 60 minutes), and hours (normally 12).
When only two sub-dials are used, the first counter to miss out is usually the hour counter.
To start the chronograph function, the pusher around the 2 o'clock position is depressed. The central seconds hand starts ticking, advancing the minute counter hand whenever it passes zero. To stop the chronograph the same pusher is depressed. To reset the stopwatch, the pusher around the 4 o'clock position is depressed. At this point, the hands all "zero" (snap back to their original position).
Other pusher set-ups exist, with single-pusher chronographs (that use one pusher for start/stop/reset operations normally at the expense of the 4 o'clock button), and mono-pusher chronographs (that have the push-piece integrated with the winding crown for a seriously clean and classic look).
Surrounding the dial on most chronographs is a decorated bezel displaying a numerical scale. These scales can be used to perform a variety of calculations. The most common scale to find on a chronograph bezel is a tachymeter. A tachymeter is used to measure the speed of an object over a known distance. Although rather esoteric, the complication was conceived to track the speed of horses or motor cars during a race. The scale can be set-up to KPH or MPH and works very simply: As soon as the object passes the "start" line, the chronograph is actuated; when the object passes the "finish" line (either 1 kilometer or 1 mile depending on the scale) the chronograph is stopped. The number the central seconds is pointing at on the scale is the speed at which the object was traveling.
Other scales that can be found on chronographs are pulsometers (for measuring a pulse), telemeters (for measuring the distance from an event that can be both heard and seen such as a thunderstorm), and the highly unusual asthmometer, which is used to track respirations per minute.
If this seldom-seen aesthetic appeals to you, check out Longines (especially the heritage collection). The famous Swatch Group brand has a reputation for releasing vintage-style chronographs printed with the more unusual scales.