Contrôle officiel suisse des chronomètres
The Contrôle officiel suisse des chronomètres , usually known as COSC for short, is the official Swiss control body for chronometers . In its current form as an association under Swiss law (Art. 60ff. ZGB ) with offices in Biel , Geneva and Le Locle , supported by the five “watch cantons” of Bern , Geneva , Neuchâtel , Solothurn and Vaud together with the Association of the Swiss Watch Industry FH it since 1973. It had emerged from the amalgamation of various private and semi-public laboratories.
Despite the term "official" contained in the name and its state collective members, the COSC is not an institution under public law and not a state-approved inspection body, but an organization recognized as a non-profit for the voluntary self-inspection of watch manufacturers.
The certification process
As the name suggests, the COSC issues quality certificates for chronometers on the basis of a standardized measurement method in accordance with NIHS 95-11 / ISO 3159.
This test of a mechanical watch lasts 15 days, in which the rate of the movement is determined in five different positions at three temperatures. The exams in detail:
- 2 days crown left at 23 ° C
- 2 days crown above at 23 ° C
- 2 days crown down at 23 ° C
- 2 days dial below at 23 ° C
- 2 days dial up at 23 ° C
- 1 day dial up at 8 ° C
- 1 day dial up at 23 ° C
- 1 day dial up at 38 ° C
- 2 days crown left at 23 ° C
All tests take place at approx. 24% humidity . The deviation is measured after every 24 hours, the movements are wound up and readjusted. On the tenth day of the exams, any complications, such as: B. a chronograph , switched on to determine their behavior on the accuracy.
After passing the test, the movement receives a corresponding certificate confirming its accuracy. It contains the following information:
| Test criterion | tolerance | ||
|---|---|---|---|
| Abbr. | Work> 20 mm | Work <20 mm | |
| medium daily gear | M. | −4 to +6 sec / day | −5 to +8 sec / day |
| mean daily rate deviation | V | Max. 2 sec / day | Max. 3.4 sec / day |
| largest rate deviation | Vmax | Max. 5 sec / day | Max. 7 sec / day |
| Difference between horizontal and vertical | D. | −6 to +8 sec / day | −8 to +10 sec / day |
| largest difference between the average daily gear and one of the gears | P | Max. 10 sec / day | Max. 15 sec / day |
| Primary compensation error (rate deviation per ° C) | C. | Max. 0.6 sec / day ° C | Max. 0.7 sec / day ° C |
| Resumption of gear (compare 1st and 2nd day with 15th day) | R. | Max. 5 sec / day | Max. 6 sec / day |
For quartz movements, the test takes 11 days and the following values apply:
| Test criterion | tolerance |
| Average daily gear at 23 ° C | Max. ± 0.07 sec / day |
| Gear at 8 ° C | Max. ± 0.2 sec / day |
| Gear at 38 ° C | Max. ± 0.2 sec / day |
| Gait stability | Max. 0.05 sec / day |
| Dynamic gait | Max. ± 0.05 sec / day |
| Temporary effect of mechanical vibrations | Max. ± 0.05 sec / day |
| Resumption of gear (compare 1st and 2nd day with 15th day) | Max. ± 0.05 sec / day |
| Residual effect of mechanical vibrations (200 blows with 100 G) | Max. ± 0.05 sec / day |
If the movement of a watch receives the COSC certificate, the manufacturer usually marks the watch with the word Chronometer .
Despite the generally high reputation of the COSC and the wide acceptance of its certificates, there are also well-known watch manufacturers, including well-known names such as Jaeger-LeCoultre , IWC , Breguet and Piaget, who are critical of the COSC and deliberately do not have their watches certified for various reasons ( or let), although these also usually meet the requirements without any problems.