How accurate is an officially tested chronometer?
If you want a particularly accurate mechanical watch, this is the correct one: chronometer is a protected term for particularly precise clocks. Only a few test sites give this quality seal–since July 2006 a German laboratory in Glashütte.
What does the term “chronometer” mean?
In fact, the word “chronometer” is the simple union of the Greek words “Chronos” for Time and “metre” for measure. Today it has a special meaning: “The” chronometer–as it is grammatically correct–is an extremely accurate clock that can present a corresponding certificate.
This certificate receives only a timepiece that is tested by an accredited laboratory and proves its accuracy in different locations and temperatures. The requirements of a chronometer must be recorded in DIN 8319 and the ISO standard 3159. These rules are implemented in different institutions. The most well-known institution is located in Switzerland: the Institut Contrôle officiel Suisse des Chronomètres, short COSC.
It is founded 1973 by five Watchmakers cantons (Berne, Geneva, Neuchâtel, Solothurn and Vaud) as well as the Association of the Swiss watchmaking industry in La Chaux-de-Fonds. The organisation comprises different laboratories, which were created independently from each other from the end of the 19th century. In addition to the board of Directors with headquarters in La Chaux-de-Fonds, there are now several outposts that can award the chronometer: so-called official control posts–”Bureaux officiels de Contrôle”–each with its own laboratory is located in Biel, Geneva and Le Locle. Each office has its own accreditation, which is granted by the Metas (Federal Office for Metrology and Accreditation) as a SCS (Swiss calibration service) laboratory. Only movements in front of the casing are tested here.
How exactly do COSC chronometers have to go?
You must have a second display and have to be Swiss through and through: All items must come from Switzerland, assembly and Reglage also take place there. In order to obtain this quality seal, i.e. to pass the chronometer exam, certain gearing must be fulfilled. There are different strict regulations–for Mechanikkaliber with a diameter of 20 millimeters and more, respectively, for calibers that are smaller in diameter.
For the smaller plants, which receive less energy from the spring and have a smaller balance, the criteria are less stringent in the accuracy of the gait than for larger plants. The small ones are allowed as the biggest change of gear at least 15 seconds deviation per day, with works of category 1 It is a maximum of ten seconds. Each plant is tested for fifteen days at three temperatures (at 23 degrees, in addition to one day at eight and 38 degrees) and five layers. The latter is of great importance, because gravity affects the friction of the cones in the bearings, the gripping point of the gears and the oscillation frequency of the balance, which in turn affects the accuracy, depending on the position of the work.
As part of the tests, the works are raised daily and measured, even on Saturdays and Sundays. Various devices are used–partly because of the special requirements developed by the COSC itself. The measurements of each movement are performed completely automatically. The movements are in transparent plastic containers from which the lift shaft protrudes. This wears a makeshift crown, so that a machine can raise the plants regularly – also the automatic works, as these are presented without rotor for testing.
The English-language video of Chopard shows in excerpts how the works are tested at the COSC:
The works are temporarily equipped with a dial with a second pitch and reference points that allow automatic reading. The plant also receives a second hand. Its position is captured by a digital video camera and analyzed with the help of digital image analysis. Between four and ten percent of the submitted works, the tests of the COSC do not exist and therefore do not receive this quality seal–because they are not accurate enough or defective and remain standing. In addition to mechanical (automatic and hand-wound) movements, the COSC also tests quartz clocks based on ISO standard 3159. They are tested for eleven days in one position at three temperatures and may deviate from the correct time at any fraction of a second. In addition, the quartz plants must also withstand 200 impacts of 100 grams, the hundred gravity of the gravitational force.
The COSC owes its internationally high profile to the fact that it is examining most of the chronometers offered: more than one million official Chronometerzertifikate are issued annually. As handsome as this number is, this corresponds to only three percent of the Swiss watch production that has received this quality seal. “This clearly emphasizes the exceptional character of the chronometer”, stresses the COSC the exclusivity of its award. After all, the manufacturer must provide demanding quality services in order to be able to crown his works as Chronometerwerke with the COSC certificate. In contrast, the fee for certification is “not very high” in its own sense.
If a watch owner wants to inquire about the test data of his chronometer, he must go the way through the manufacturer–the data is subject to data protection; End customers will not receive any information. The same is true for the desire to have an older wristwatch tested again for its accuracy.
How exclusive are watches with COSC chronometer certificate?
Since the late 1980s, COSC has registered a significant increase in Chronometerzertifizierungen. Until 1988 the number moves at below 500,000, then it continuously rises to the peak of over 1,470,000 in the year 2007 – that is 13.3 percent more than 2006. About five percent of them were quartz watches – almost all from Breitling. The figures for 2008 can even top this result: 1,676,515 works receive the certificate, of which 1,563,950 are mechanical. Rolex has been the largest customer for years. In the year 2009, the 607,512 works delivered by the watch brand made up almost half of the movements tested by the COSC. Thereafter, Omega followed with 187,558, Breitling with 108,220 and Tag Heuer with 70,195 works.
Such figures emphasize the position of COSC against Chronometerprüfungen in other European countries. These are carried out, for example, in France, where the Société française of Microtechniques et de chronometrie S.F.M.C. tests chronometers in the observatory of Besançon; And now again in Germany: Since July 2006, in Glashütte under the aegis of the State Office for Metrology and Calibration Thuringia (LMET) chronometers are tested.
Air conditioning: Witschi devices in the climate cabinets
The Test centre is located in the historic observatory Urania, which has been extensively renovated by jeweller Wempe and recently expanded to include a new building. There, Wempe manufactures its own clocks and houses the only German Chronometerprüfstelle, which operates the state Office for Metrology and calibration in Thuringia (LMET) in cooperation with the Saxon National Agency for Metrology and Calibration (SLME) as a branch. A cooperation agreement stipulates that WEMPE will provide the personnel led by the LMET as well as the equipment.
How do the glashütter chronometers differ from those of the COSC?
The test of the clocks is carried out in accordance with the DIN EN ISO/IEC 17025 regulation. The test duration and the permissible maximum gear deviations correspond to those of the COSC check. There is, however, a decisive difference: While the C.O.S.C. checks the naked movement, the German Chronometerprüfstelle tests the switched-on, finished watches as they arrive later at the customer. Serial numbers of the plant and housing are recorded in the so-called “Calibration certificate”. If the wearer of a COSC-certified watch only knows that his work in the test laboratory complied with the prescribed values, the owner of a clock certified in Glashütte as a chronometer has the certainty that the watch itself passed the tests and received the quality seal.
In Glashütte, the finished watches prove for 15 days at different temperatures and in five conditions that the second hand of a mechanical clock Class 1 is at most a median deviation of minus four to plus six seconds per day to blame Can. The watches are in the context of the tests in climatic cabinets in which test facilities of the Swiss company Witschi are used. In the cupboards there are temperatures of eight to 38 degrees and an air humidity of about 60 percent. During the tests, computers record the measured values of each individual clock, display them on screens, and then save them.
What quality seals for watches are there yet?
In addition to the chronometer test, there are other seal of approval: The Geneva Punze, also known as the Geneva seal, the Patek Philippe Siegel, the Metas Certificate of Omega and the qualité Fleurier.
Tags: Breitling, Chopard watches, chronometer, Rolex, Tag Heuer
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