Then, for 15 days for wristwatches and pocket watches, 19 days for carriage clocks and on-board clocks, and 13 days for quartz timekeeping instruments – a long and rigorous time period – the parts undergo daily tests. Every day, including weekends, the instruments are measured and wound. On the basis of the measurements, 7 elimination criteria are calculated for Type I. If and only if the 7 criteria are met, the movement / watch is certified as a chronometer.
What are the 7 criteria?
- average daily rate
- mean variation in rates
- greatest variation in rates
- the difference between rates in horizontal and vertical positions
- largest variation in rates
- variation in rate depending on temperature
- rate resumption