The seconds hand is fundamental in watches, especially in the automatic ones, since it indicates the flow of time, and shows the correct functioning of the watch.
In mechanical watches, the seconds’ hand is naturally decentrated, because it is placed on the second’ wheel. By modifying the wheel train, thus adding a complication to the watch, the seconds’ hand can be placed at the center of the dial.
Seconds’ hand usually makes a small jump each vibration of the balance wheel. A common beat in watches is 3Hz, 21.600 vibrations per hour, meaning that the seconds’ hand makes 6 jumps in a second.
But watchmaking industry offers more sophisticated options to display the seconds’ flow.
The independent dead seconds watches have a central seconds’ hand unique for its move. It makes a sole jump every second. An additional wheel train lets the hand being independent from the escapement wheel movement, that makes a small jump every 1/6 of a seconds in watches beating 21.600 vibrations per hour. Given this additional wheel train, it is possible to stop the second hand without stopping the movement of the balance wheel. In this way, a precision regulation at the second is possible. Independent dead seconds are today a very rare complication, suitable only for exclusive mechanical watches. Some of them are the Tourbillon Souverain from F.P.Journe and the Portuguese Sidérale Scafusia from IWC.
Watches with foudroyantes seconds have two hands dedicated to seconds: the central one, with a regular move of one turn in one minute, and a smaller one, that makes fast jumps one each 1/6 of the seconds (in watches beating 21.600 vibrations per hour). This small hand, as for the independent dead seconds, is moved by an additional wheel train, based on a steel star that is activated once every vibration of the balance wheel. The foudroyantes seconds are a rare complication too, that you can appreciate, for example, on the fascinating models “Duomètre” by Jaeger-LeCoultre.
Another interesting complication regarding the seconds hand is the “Zero-reset” mechanism. When the crown is pulled, the seconds hand snaps back to zero, letting you set to the exact minute on-demand, accurate to the second. The zero-reset mechanism is now placed in many watches currently on production. Its highest celebration comes from A. Lange & Söhne, which introduced this year the 1815 Tourbillon with the “Zero-reset” mechanism.