Oscillators play a crucial role in various timekeeping devices, including church clocks, pocket watches, mechanical watches, and quartz wristwatches. Despite their different appearances and mechanisms, the fundamental purpose of oscillators remains consistent—to establish a precise and steady rhythm. In this article, we will delve into the different types of oscillators found in the watch world, exploring their functionality as well as their respective advantages and disadvantages.
At its core, an oscillator is a mechanism that converts energy into periodic oscillations. These movements typically revolve around a central point, often referred to as the oscillator's idle position. When it comes to timekeeping devices, oscillators generate a harmonic damped oscillation, characterized by high regularity. However, without sufficient energy supply, the oscillation gradually loses momentum until it comes to a stop.
Mechanical wristwatches and pocket watches rely on the balance wheel as their oscillator, while mechanical church clocks and grandfather clocks utilize a pendulum. On the other hand, quartz watches and smartwatches employ a quartz crystal to establish their rhythm. In all cases, the higher the frequency of the oscillator, the more precise the timekeeping device becomes.
Let's take a closer look at the two most common oscillator types—balance wheels and quartz oscillators—particularly those used in wristwatches for simplicity.
The balance wheel, patented in 1675 by Dutch scientist Christiaan Huygens, comprises a balance rim, hairspring, and central balance staff. As the hairspring, a wafer-thin wire, imparts tension, the balance rim oscillates back and forth. This oscillation releases the escapement at regular intervals, regulating the energy flow within the watch. The energy is then transmitted to the gear train and eventually powers the watch's hands. The frequency of this oscillation varies between 2.5 Hz and 5 Hz, or 18,000 to 36,000 vibrations per hour (vph). Modern mechanical movements typically operate at 21,600 to 28,800 vph (3.5 to 4 Hz).
To ensure accurate timekeeping, the balance wheel's oscillation rate requires meticulous adjustment. Watchmakers strive for even oscillation and an appropriate amplitude (maximum deflection of the balance wheel). Regulators are used to fine-tune the tension of the hairspring, while small weights can be added to the balance rim for balancing purposes. Additionally, shock protection systems are integrated to prevent the balance wheel from being disrupted by external shocks and vibrations. However, mechanical watches with magnetic balance springs are susceptible to magnetic fields.
Quartz oscillators, unlike balance wheels, lack mechanical components and consist of a quartz crystal and a circuit. Analog quartz watches use a battery as the energy source, with a stepping motor acting as the escapement. Applying electrical voltage to the quartz crystal induces vibrations due to the piezoelectric effect. The crystal's size and shape determine the vibration speed, typically set to the industry standard of precisely 32,768 kHz (32,768 vibrations per second). A circuit reads these vibrations, translating them into one pulse per second, which triggers the stepping motor to advance the second hand.
Quartz watches offer higher accuracy compared to mechanical watches. While a quartz watch may deviate by only 10 to 30 seconds per month, certain mechanical watches can deviate that much in a single day. Additionally, quartz watches require less maintenance, as they contain fewer mechanical components and are resistant to vibrations and magnetic fields. They also eliminate the need for daily winding, with the battery requiring replacement every few years.
Despite the advantages, quartz watches often receive less recognition from watch enthusiasts due to the perception that they lack soul and craftsmanship. Mechanical movements are typically considered more desirable, symbolizing intricate craftsmanship and handwork. However, exceptions exist, such as Rolex's Oysterquartz movements.
In addition to balance wheels and quartz oscillators, there have been attempts to innovate and revolutionize oscillators in watchmaking. Notably, Seiko's Spring Drive combines the precision of quartz crystal oscillation with the allure of a mechanical movement. Zenith has also introduced the "Zenith Oscillator," a monocrystalline silicon component that replaces both the balance wheel and escapement, boasting exceptional precision at 15 Hz.
In conclusion, oscillators are vital components in timekeeping devices, setting their pace with accuracy and stability. Balance wheels and quartz oscillators are the most commonly used types in wristwatches, each with its distinct advantages and considerations. While balance wheels showcase mechanical craftsmanship, quartz oscillators offer higher accuracy and lower maintenance requirements. The choice between them ultimately depends on personal preferences and the desired characteristics of the timepiece.