|
 Precision
and accuracy aren't the same thing.
As Alan Downing points out in his
"Inside COSC" article for TimeZone:
"...a watch that gains 15 seconds a
day might not be accurate, but if it gains (or loses) exactly the same
amount every day, it is extremely precise.
"High precision can be adjusted to
accuracy, but low precision indicates inherent faults...."
So much for those nincompoops fond of
mindlessly insisting, "The most accurate watch is a stopped watch."
Omega definition of "chronometer"
 |
Variation of between not more than -4
and +6 seconds per day
|
|
This equates to a 99.99% precision
|
Omega mechanical watch design
standard
|
Variation of between not more than -1
and +6 seconds per day
|
In evaluating my own Omega watches,
timekeeping accuracy must average a daily variation of not more than -1
and +6 seconds per day — over the course of a 15-day comparison against
the
US Navel Observatory Master Clock.
Bluntly put, this is part of the performance guarantee I am purchasing
from Omega, based on its own representations.
Mechanical watches without
certificates
|
"The majority ... have average precision tolerances of between -1
and +11 seconds per day," according to Omega |
Omega quartz movements
|
Accurate to within "variations of
between -0.5 and +0.7 seconds per day." |
By my math, that makes a quartz
movement somewhere between 1½ and 12 times as accurate as its COSC-certified mechanical counterpart. |
