In watchmaking, the terms ‘chronometer’ and ‘chronograph’ are frequently used. While novices may use the terms interchangeably or simply refer to them as ‘chrono’, it is important to note that they actually refer to two distinct objects.
The chronometer
The term refers to a timekeeping instrument that has been certified as accurate by an official, neutral and independent body.
In Switzerland, the COSC (Swiss Official Chronometer Testing Institute) tests a large number of unassembled watch movements. In France, the Besançon Observatory certifies the performance of watches in accordance with ISO 3159:1996. Since 1897, the ‘Viper’ hallmark has been used to certify the perfect regularity of movements tested by this French observatory.
Therefore, a chronometer is a watch that has passed extremely rigorous accuracy tests. These tests are carried out under various conditions, such as movement, turbulence, temperature, duration, humidity, shock and pressure. A chronometer’s timekeeping variation must not exceed -4/+6 seconds per day.
A chronometer watch is a mark of excellent quality, often featuring a high standard of finish. Zenith’s Calibre 135, for example, is a chronometer renowned for its reliability.
The chronograph. Or the chronograph watch.
This is a watch fitted with a complication, in this particular case a timing function that allows precise durations or time intervals to be measured.
A chronograph typically has buttons for starting, stopping and resetting a specific hand. They are useful for many things, such as timing a lap, calculating the speed of an object or monitoring a patient’s heart rate.
Furthermore, a chronograph watch may have up to three additional dials designed to measure seconds, minutes and hours. These instruments can offer extreme precision, measuring time down to a fifth, tenth or even hundredth of a second. However, it is important to note that a chronograph is not necessarily a chronometer. Only watches that have successfully passed the certification tests are entitled to bear this title.
One of the most legendary chronographs is the Omega Speedmaster. This was the first watch to be worn on the moon.
This article is illustrated by a short video.
In short, a chronograph is a watch with a stopwatch function, while a chronometer is a watch whose accuracy has been certified. A watch can be both if it has a chronograph function and has been certified as a chronometer.
