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What is a Chronometer Watch?

10/31/2013 4:10:43 PM | by Anonymous


A chronometer watch is a type of watch that has been tested by and met with the standard criteria for the precision of the Contrôle Officiel Suisse des Chronomètres (COSC), the Official Swiss Chronometer Testing Institute. It is important that a chronometer watch must not lose more than four or gain more than six seconds per day. About one million watches are certified as chronometers every year. This makes up a total of 3% Swiss watch productions. These types of watch are typically made of high quality materials and parts.


A certified chronometer is a high precision watch that is capable of displaying the seconds. They have been tested and certified by the official neutral body. Each chronometer watch is unique to its own. They are identified by a number that is engraved on its movement and a certification number that is provided by the COSC. Each movement is individually tested for days in different temperatures and positions. Any watch with the denomination “chronometer” is provided with a certified movement.


The COSC states that a timepiece has to meet the standards that are compiled under a rubric known as the ISO 3159 in order to be called a chronometer watch. In the 15 day test process, a particular watch movement is measured at five different positions at three different temperatures. Seven of the criteria have to be met in order to be certified as a chronometer watch. The seven criteria include:


1. Consistency in the average rate over the initial 10 test days

2. Mean variations in time

3. The largest difference between two days readings at a single position

4. The difference between the rates in vertical and horizontal positions

5. The largest difference between the mean daily rate and any individual rate during the initial 10 days of testing

6. The temperature error of the movement that is measured in seconds per degree

7. Rate resumption


Rate resumption is calculated by the subtraction of the average mean daily rate from the first two days of testing, inclusive from the mean daily rate of the last test day. Each of the testing measurements is then compared against the atomic clocks to ensure absolute accuracy. A watch is only then certified to be chronometer after meeting all the requirements that have been set.


On top of just meeting these stringent requirements, a chronometer watch must also incorporate rare components in order to increase their precision and efficiency. This would include sapphire or ruby jewel bearings to decrease the friction and wear and tear of the pivots as well as exotic metals for example platinum or titanium that are taken advantage of their prestigious outlook.


These timepieces would commonly include one or more features that are known as complications. This can range from a perpetual calendar to a display that shows the phases of the moon. Complications as inferred from the name are built within the watch mechanisms and contributed to its complexity.


Though it is not technically a complication according to most watch makers, the most famous of these mechanical additions are the tour billion. It is French for whirl wind. The tour billion was originally designed to counter the effects of gravity when a watch movement was rotated.


However, in today’s use they are largely relegated to ornamental statuses. Tours billions are still seen as the most expensive and complex types of chronometer watches till date which explains why they are often left exposed to display their inner workings.


Through the development of quartz movement from the 1960s to the 1970s, it has made the chronometer watch obsolete from the technical standpoint as they continue to enjoy the healthy sales revenue due to their precision engineering and aesthetic qualities.


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