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    Re: Chronometers
    From: Alexandre Eremenko
    Date: 2008 Mar 29, 23:03 -0400

    Dear Lu,
    This specification does not tell us much on comparison
    of railroad watches with chronometers.
    Let us compare the essential parameters.
    (I use the certificate of a Soviet chronometer of
    "Class II" made in 1980-s.
    > */American made 18 or 16 size /* (Soviet made)
    > /*Fitted with 17 or more jewels [21 was most common] (21)
    > /*Temperature compensated*/      (Yes)
    > /*Adjusted to 5 positions*/  (Jimbals. No need to adjust)
    > /*Lever Set*/                (No setting)
    > /*Timed to +/- 30 sec/week*/ (3.5 sec per day)
    > /* Plain white dial *//*having:*/   (Yes)
    > /*Black Arabic numerals*/           (Yes)
    > /*Each minute delineated*/ (Yes, and each second).
    Additional parameters in specification:
    average deviation of daily rate: 0.35 sec.
    rate recovery:                    2 sec.
    maximal variation of the daily rate: 2.3 sec.
    secondary error of compensation:   1.2 sec.
    Let me explain these parameters.
    Chronometers were tested for 5
    consecutive periods of 5 days each,
    each period under constant temperature, and the
    temperatures were: 36, 20, 4, 20, 36 (Celsius).
    The rate deviation was recorded for every day.
    Now it is clear what the average rate deviation is,
    just the average of these 25 numbers.
    Rate recovery is the average rate on the fifth period
    minus average rate of the first period (they are at the
    same temperature).
    Maximal variation is the maximal difference of rates
    in two consecutive days.
    And "secondary error in compensation" is the
    average rate at 36 and at 4 degrees, minus the
    average rate at 20 degrees.
    (I would call this last quantity "non-linearity of
    the temperature compensation").
    P.S. I don't know how to reproduce this testing at home.
    To let it run 5 days in a refrigerator? :-)
    Navigation List archive: www.fer3.com/arc
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