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    Re: Chronometers
    From: Lu Abel
    Date: 2008 Mar 29, 22:38 -0700

    I certainly didn't intend to argue the performance of a marine
    chronometer against a railroad watch from almost a century earlier.  I
    was merely responding to a comment that a professional mariner owned a
    railroad watch and "swore by it" with a specification for such a
    watch.   Thanks for taking the time to do a comparison of specifications.
    
    Lu
    
    Alexandre E Eremenko wrote:
    > 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").
    >
    > Alex.
    >
    > P.S. I don't know how to reproduce this testing at home.
    > To let it run 5 days in a refrigerator? :-)
    >
    >
    > >
    >
    
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