Glossary · Regulation
Beat error
Timing asymmetry between alternate balance beats, reported in milliseconds by a timing machine.
Explanation
Beat error describes the asymmetry of alternate beats as detected by a timing instrument. It is not the watch's daily gain or loss, and it is not amplitude. In a lever watch it relates to the relationship between the balance's rest position and the escapement's impulse action. A watch can have a small daily rate error and still be out of beat; conversely, a low beat-error reading does not establish that the rest of the movement is healthy.
Adjustment depends on construction. Some calibres have a movable stud carrier, while others require specialist work on the hairspring's attachment. The rate index and the stud carrier do different jobs and must not be confused. Record the instrument's reading together with position, wind state, rate and amplitude. A noisy or unstable trace needs interpretation before any adjustment is proposed; a single photograph cannot identify a bent spring or worn pivot.
Sources & references
- https://wahawatches.com/watch-talk-whats-the-beat-error-of-a-watch/
- de Carle, D., Practical Watch Repairing — technical further reading; exact procedures require calibre documentation
Where sources disagree, the disagreement is stated rather than resolved silently.
What to record
- Record milliseconds separately from seconds-per-day rate.
- Keep test position and wind state with the trace.
- Identify the calibre and stud arrangement before interpreting adjustment.
Do not move a hairspring collet or stud carrier on an unfamiliar movement; these are delicate specialist adjustments.