Chronograph or Chronometer ?
At present, there is no dedicated standard to certifying the precision of a chronograph.
Chronograph or chronometer ?
A chronograph is a complication on a watch that makes it possible to measure an interval of time. A chronometer is a high-precision watch that has been tested and certified by the COSC. This label is given to a precision timekeeping instrument set for various conditions of use (e.g.those of ISO 3159 for mechanical chronometer wristwatch).
FAQ
What is a COSC certified watch?
In order to know if a watch is COSC-certified, you can check whether it bears the designation of “chronometer.” This designation is awarded only to watches that have passed the COSC's rigorous precision tests. As a general rule, certified watches are accompanied by a chronometer certificate, although this is optional and depends on the watch brand. If you have any doubts, it is advisable to contact the watch manufacturer directly for information regarding certification.
How to check a watch's precision?
In order to verify the precision of a watch, it is essential to follow several steps to assess its performance in relation to a time reference. Here are some commonly used methods:
-Use of a reference clock: Compare the time indicated by your watch with an atomic clock or a radio-controlled clock, which are extremely precise sources of time.
-Observation over several days: Note the time on your watch at a specific time each day and compare it with the reference time. Calculate the daily difference to determine if your watch is running early or lagging behind.
-Testing in different positions: Mechanical watches can vary in precision depending on their position (dial facing upwards, dial facing downwards, sideways). Test the watch in different positions to see if this affects its precision.
-Temperature monitoring: The precision of a watch can be affected by temperature. Try to check whether temperature variations affect the operation of your watch.
-Use of applications or measuring devices: There are applications and electronic devices that can help measure a watch's precision by recording the movement's beats and comparing them with a time reference.
These methods make it possible to determine the regularity and precision of a watch, ensuring that it operates within the tolerances acceptable for a certified chronometer, such as those defined by the COSC.
What should the precision of a chronometer be?
The precision of a COSC-certified chronometer must be between -4 and +6 seconds per day. While this tolerance may seem high, it is in fact the result of extraordinary requirements. Even if a watch gained 6 seconds every day, it demonstrates remarkable regularity. Using the metric system for comparison, the error over a year's time would be equivalent to about 7cm for every 1000m. Mechanical watches, in particular, partially compensate for their deviations as a function of temperature and position, which is an essential quality of these high-quality watches.