Patek Philippe CH 28-520 C FUS, Manual, Page: 18 / 116

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quality control
The movements and completely assembled watches
are subject to a series of technical tests and visual
inspections to verify their rate accuracy, winding
speed, power reserve, reliability, water resistance,
and overall appearance. After it was assembled,
your self-winding watch will already have run for
several weeks before leaving the workshops; it
fully complies with the stringent criteria of the
Patek Philippe Seal.
rate accuracy
The rate accuracy of Patek Philippe watches is veri-
fied in several phases of manufacturing, both with
uncased and fully cased movements. The final test
is performed with a wrist motion simulator and
the results must conform to the following Patek
Philippe precision benchmarks:
The rate accuracy of calibers with a diameter of 20 mm or
larger must range within –
3 and + 2 seconds per 24 hours.
The precision of a watch is determined by how
accurately it keeps the time. A watch that is fast or
slow is considered precise if the amount by which
it is fast or slow remains constant. Such a devia-
tion can be easily corrected. Consequently, the last
test of accuracy takes place on your wrist. Your
temperament or the nature of your physical activi-
ties can cause slight irregularities. Fluctuations in
position, temperature, or air pressure, the presence
of magnetic fields (as produced by most electronic
devices, metal detectors, household appliances,
etc.) as well as vibrations and other factors may
also affect its accuracy.