NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Chronometers
From: Lu Abel
Date: 2008 Mar 29, 22:38 -0700
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? :-) > > > > > --~--~---------~--~----~------------~-------~--~----~ Navigation List archive: www.fer3.com/arc To post, email NavList@fer3.com To , email NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---