Chronometer Certificate - BMW Ball Manual Del Usuario

Chronometer Certificate
A Chronometer is an extremely accurate watch. It takes its name
from the Greek words chronos + metron meaning "to measure
time". A BALL chronometer is a highly accurate, mechanical watch
whose precision has been tested and verified by The Official
Swiss Chronometer Testing Institute (Contrôle Officiel Suisse des
Chronomètres, or COSC, in French).
Before issuing the certificate, the COSC conducts elaborate precision
tests on each BALL movement using cameras and computers and
analyzes the data. The COSC performs seven different tests. Failure
to meet the minimum standard in any one of the tests means that
a movement is rejected. Here is a brief summary of the testing
procedures:
※ Test 1
Mean daily rate: After 10 days of tests, the mean daily rate of the
movement must be within the range of -4 to +6 seconds per day.
The COSC determines the mean daily rate by subtracting the time
indicated by the movement 24 hours earlier from the time indicated
on the day of observation.
※ Test 2
Mean variation in rates: The COSC observes the movement rate in
five different positions (two horizontal, three vertical) each day over
10 days for a total of 50 rates. The mean variation in rates can't be
more than 2 seconds.
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※ Test 3
Greatest variation in rates: The greatest of the five variations in rates
in the five positions can't be more than 5 seconds per day.
※ Test 4
Horizontal and vertical difference: The COSC subtracts the average
of the rates in the vertical position (on the first and second days) from
the average of the rates in the horizontal position (on the ninth and
tenth days). The difference must be no more than -6 to +8 seconds.
※ Test 5
Greatest deviation in rates: The difference between the greatest daily
rate and the mean daily test rate can't be more than 10 seconds
per day.
※ Test 6
Rate variation due to the temperature: The COSC tests the
movement's rate at 8 degrees Celsius (46 degrees Fahrenheit) and
at 38 degrees Celsius (100 degrees Fahrenheit). It subtracts the cold
temperature rate from the hot temperature rate and divides by 30.
The variation must be no more than 0.6 seconds per day.
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