WatchesAtlas / Watch knowledge
The Watch Encyclopedia
Understand the details that make a watch.
40 terms
Clear filtersAccuracy
How closely a watch's indicated time corresponds to a reference over a stated interval.
Performance & measurementAdjustment in positions
Work intended to reduce differences in a movement's running behaviour across specified orientations.
Performance & measurementAmplitude
The angular extent of a balance wheel's swing, measured under stated test conditions.
Performance & measurementATM
A pressure unit often used in water-resistance markings.
Performance & measurementBar
A unit of pressure used in watch water-resistance specifications.
Performance & measurementBeat error
A measure of asymmetry between alternating beats of a mechanical movement, commonly assessed with a timing instrument.
Performance & measurementBPH
The number of half-oscillations or beats of a regulating system in one hour.
Performance & measurementChronometer
A designation relating to timekeeping performance established through a defined testing or certification process.
Performance & measurementCOSC
The Swiss organisation certifying chronometer performance through defined tests.
Performance & measurementGauss
A unit used to express magnetic flux density in watch specifications.
Performance & measurementHertz
A unit of frequency expressing complete cycles per second.
Performance & measurementHigh-accuracy quartz
A broad description for quartz watches designed to deliver enhanced timekeeping performance under stated conditions.
Performance & measurementHigh-beat movement
A movement operating at a relatively high oscillator frequency compared with its relevant mechanical peers.
Performance & measurementInstantaneous rate
A running-rate estimate relating to the conditions and short observation period of a particular measurement.
Performance & measurementIP rating
A classification of protection against specified forms of solid-particle and water ingress, with conditions depending on the rating.
Performance & measurementISO 22810
An international standard addressing water-resistant watches and the test methods used to assess water resistance.
Performance & measurementISO 3159
An international standard concerning wrist chronometers with a spring-balance oscillator and their performance assessment.
Performance & measurementISO 6425
An international standard addressing divers' watches and their specified requirements and test methods.
Performance & measurementIsochronism
The extent to which an oscillator's period remains consistent as its amplitude or energy state changes.
Performance & measurementLift angle
An escapement-related angle required by many timing instruments when calculating balance amplitude.
Performance & measurementLigne
A traditional watchmaking length unit often used to describe movement dimensions.
Performance & measurementMagnetic resistance
A watch's ability to maintain specified operation in the presence of magnetic fields under stated conditions.
Performance & measurementMagnetisation
The acquisition of a magnetic state by susceptible components, potentially affecting their behaviour.
Performance & measurementMaster Chronometer
A certification designation involving tests of the complete watch under a METAS-approved framework.
Performance & measurementMean daily rate
An average daily gain or loss derived from a defined set of observations or test conditions.
Performance & measurementMillimetre
A length unit commonly used for case dimensions, lug spacing and movement measurements.
Performance & measurementParts per million
A relative measurement used to express small deviations, including selected oscillator accuracy specifications.
Performance & measurementPositional error
A difference in timekeeping behaviour associated with the watch's orientation during a test or use.
Performance & measurementPositional variation
Differences in rate when a watch is tested in different orientations.
Performance & measurementPower reserve
The stated or measured time a watch can run after reaching its specified energy state before stopping.