Since time immemorial, people have strived to measure and display time as accurately as possible. Sundials were an early ideal solution because their readings follow the ultimate conductor of time itself. The catch: they only work in fine weather. That is why the idea of giving clocks and watches more independence with an oscillator was nothing short of brilliant.
Ideal for Timekeeping – Frequency-Stable Pendulum Motion
In experiments, Galileo Galilei established in 1632 that a pendulum's period is independent of its weight and largely unaffected by its amplitude. The latter holds true especially for small swings. What does matter is the length of the pendulum. A pendulum just under one meter long, for example, takes one second to swing from one side to the other.
On top of that, pendulum motion is comparatively frequency-stable, which is essential for timekeeping. Anyone can see this for themselves, since a children's swing is a playful take on the pendulum: the combination of suspension and seat dictates the frequency at which you swing. Attempts to change it significantly are doomed to fail. Galileo recognized the significance of his findings for timekeeping instruments but never pursued the idea further.
The Heart of Horological History: The Gravity Pendulum and the Balance Wheel
Christiaan Huygens drew inspiration from Galileo's law of the pendulum and concluded that an oscillator in a clock must be designed so that it can sustain its natural oscillation steadily over a long period. To that end, he designed the gravity pendulum in the form we know today and had the first pendulum clock built in 1657. The astronomer realized that his concept was only suitable for stationary clocks. He therefore worked on a pivoted wheel, which was ready for the market in 1674. This so-called balance wheel has served ever since as the oscillator in timepieces meant to work regardless of position. Thanks to improved materials, tools, and techniques, the component was miniaturized until it fit inside wristwatches.
Watch connoisseurs know that, strictly speaking, Huygens' invention consists of the pivoted oscillating body and a balance spring that regulates the oscillation frequency. Such an oscillating system is called an oscillator. The term is also used for classic clock pendulums, since they likewise combine several functions of an oscillating system.
Oscillators That Are Hard to Disturb
The core goal of watchmaking is to reproduce standard time as accurately as possible. In the 17th century, it was groundbreaking that Huygens' pendulum clock deviated by only 10 seconds a day. Inventors were not content with that. They experimented with oscillating bodies such as torsion pendulums, which allowed torsion pendulum clocks to achieve enormous power reserves. More than 80 years ago, the special alloy Nivarox brought major progress in optimizing the material of oscillators. Temperature, air resistance, or humidity: the more effectively external influences were curbed, the more accurate timepieces became.
Ambitious watchmakers also quickly realized that increasing the beat rate has a positive effect on accuracy. This applies especially to wristwatches, which are exposed to influences such as shocks. The goal was thus clear: to integrate the highest-frequency oscillators possible into timepieces, while keeping them small and their amplitudes low.
Tiny Frequency Marvels: Tuning Fork Oscillators in Watches
In mechanical wristwatches, the balance wheel now achieves 18,000 to 36,000 vibrations per hour. That corresponds to frequencies of 2.5 to 5 hertz (Hz). Heritage brands continue to push mechanical precision timekeeping forward to this day. One example is the Slimline watches from Frederique Constant, which impressed with a frequency of 40 Hz when they debuted in 2021.
This increase in frequency is remarkable in the realm of mechanical regulation. Compared with visionary watch legends, however, it seems modest. In 1921, Max Hetzel had the flash of inspiration to introduce tuning fork-shaped oscillators. It took forty years for the concept to become market-ready and define the Bulova Accutron. It impressed with an oscillation frequency of 360 Hz, which reduced deviations to 60 seconds per month. The electrically powered tuning fork watch sold millions of units but was quickly displaced by the next innovation.
High-Speed Oscillators Made of Quartz
In 1880, Jacques and Pierre Curie discovered that when a quartz crystal is elastically deformed, its electric poles shift, generating an electric voltage. Conversely, the crystals deform when an electric voltage is applied to them. This is known as the piezoelectric effect, and it explains why quartz crystals are used as oscillators in watches. They oscillate at high frequency and take up little space, which benefits accuracy. Warren Marrison presented a working quartz clock in 1928. Ten years later, laboratories were able to buy the first precision quartz clocks.
The Quartz Wristwatch
The performance of quartz oscillators improved when, due to the scarcity of natural crystals, manufacturers switched to synthetic production using quartz sand. This made it possible to influence the crystal structure so that it became, for example, insensitive to pressure and temperature-stable. Further challenges were overcome until production-ready quartz wristwatches were introduced in the early 1970s. Debutants with lab-grown oscillators were greeted with applause, such as the Seiko Astron, the Junghans Astro-Quartz, or the Hamilton watch Pulsar.
Tech enthusiasts were amazed that the first luxury quartz watches came close to breaking the 10,000 hertz mark in oscillation frequency. Soon afterward, conceptual improvements and practical considerations led to tuning fork-shaped quartz oscillators at 32,768 Hz being established as the standard. Combined with a high level of manufacturing expertise at the watchmaker, deviations are limited to 60 seconds per year. By comparison, mechanical luxury watches are already celebrated when their rate deviation is limited to 2 seconds per day.
Beyond wristwatches, quartz as an oscillator is surpassed only by the chemical element cesium, which defines the conventional atomic clock. Its development gained momentum when key insights into magnetic resonance – essential for magnetic resonance imaging – were achieved in 1940. Its tiny error rate was sensational, amounting to one second in 30 million years. The cesium clock, which incidentally also contains a quartz crystal, has since been surpassed by atomic clocks using laser light pulses. Their rate deviation is one second in 100 trillion years.
No Convincing Performance Without a Perfect Ensemble
Every oscillator is slowed down by damping. It therefore needs energy to get going and keep going. This is supplied by weights, mainsprings, or batteries. Without another ingenious invention for the movement, this energy would simply dissipate: the escapement. Only in interaction with numerous components does an oscillator become a timekeeper whose transmitted impulses correspond to one second. Pendulum, balance wheel, and quartz oscillator: their quality only shows when every component is excellent in its own right and perfectly matched to the others. Oscillators of various kinds can thus be found in both mechanical and quartz wristwatches, albeit very different ones.
What Does the Oscillator in a Watch Do?
This question would be inadequately answered by focusing solely on oscillation. With its recurring swings, the oscillator not only keeps timepieces in motion but also controls how they run. That is why watchmakers also call it the regulator.
