THE JOURNAL

For beginners - 20 watch evaluation metrics explained

News centrePublished 2014-04-02

1. Instantaneous error: The difference between the time indicated by the watch at any given moment and the standard time.
2 Daily rate: The difference in the actual timekeeping of a watch over a twenty-four-hour period.
3. Instantaneous daily rate: The daily rate value measured by testing instruments over a short period under specified environmental conditions.
4. Mean daily rate: The average value of a watch's daily rate over several days.
5. Daily variation: The difference between the daily rate and the mean daily rate.
6. Mean daily variation: The average value of the daily variation over several days.
7. Daily rate change: The difference in daily rate between two consecutive days.
8. Mean daily rate change: The average value of the daily rate change over several days.
9. Isochronism error: The difference in instantaneous daily rate between a fully wound watch and one after 24 hours, measured in various positions. The maximum difference is typically taken as the isochronism error.
10. Positional error: The maximum difference in instantaneous daily rate measured in various positions when the watch is fully wound.
11. Amplitude: The angular displacement of the balance wheel from one extreme position to the other.
12. Full-wind amplitude variation between flat and vertical positions: The maximum difference in amplitude between the dial-up position and various vertical positions when the watch is fully wound.
13. Full-wind vs half-wind amplitude difference: The difference in amplitude in the dial-up position between a fully wound watch and one after 24 hours.
14. Half-wind amplitude: The amplitude of a watch in the 24 “ 3 ” position after hours from a full wind.
15. Temperature coefficient: The change in a watch's daily rate for every 1°C change in temperature.
16. Comprehensive index: A parameter reflecting the internal quality of the watch movement, calculated by combining isochronism error, positional error, and temperature coefficient in a specific ratio value.
17. Recovery error: The difference in daily rate in the same position between the final day of a test period and the start of the test.
18. Power reserve: Refers to the duration a watch can maintain timekeeping after being fully wound.
19. Period: Refers to the time taken for one complete oscillation of the balance wheel in the watch's regulating mechanism.
20. Frequency: The frequency of a mechanical watch refers to the number of full oscillations of the balance wheel per second, measured in Hertz (Hz). In practical application, it can also be expressed using the corresponding number of oscillations (beats per second) or (beats per hour) .

Hz beats/second beats/hour
   5/2　　5　　　18000
11/4　　11/2　　19800
   3　　 6　　　21600
7/2 　　 7　　　25200
4 　　　8　　　28800
5　    　10　　　36000

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For beginners - 20 watch evaluation metrics explained

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