Whether you open up a church clock, pocket watch, mechanical watch, or quartz wristwatch, you’re bound to find an oscillator. Although this assembly can look and work differently depending on the timekeeping device it’s used in, its purpose is always the same: to set as precise and steady a pace as possible. In this article, we’re digging deep into the common oscillator types in the watch world, explaining how they work as well as their pros and cons.
What is an oscillator?
Broadly speaking, an oscillator is a mechanism that transforms energy into a periodic oscillation. This movement usually takes place around a central point, which is almost always the oscillator’s idle position. The oscillators used in timekeeping devices generate a harmonic damped oscillation. This means that the oscillation is very regular and, unless supplied with sufficient energy, will continue to lose momentum until it eventually stops.
In mechanical wristwatches and pocket watches, the balance wheel takes on the role of oscillator, while church clocks and grandfather clocks with mechanical movements typically use a pendulum. Quartz watches and smartwatches have a quartz crystal to set their rhythm. In any case, the faster the oscillator is, the higher the frequency and thus the more precise the timekeeping device is.
How Different Oscillators Work
Let’s take a closer look at the most common kinds of oscillators. To keep things simple, we’ll focus on oscillator systems used in wristwatches. The balance wheel and the quartz oscillator are by far the most widely used.
The Balance Wheel
The balance wheel was patented way back in 1675. It was developed by Dutch scientist Christiaan Huygens, who had already gained recognition for his work in the development of pendulum clocks.
The balance wheel consists of a balance rim, hairspring, and central balance staff. The rim, usually a thin ring, is moved back and forth by the hairspring, which is made of a wafer-thin wire. This movement is used to release the escapement, which regulates the flow of energy in the watch, at regular intervals. This energy is then transferred to the gear train and finally to the hands of the watch. Depending on the construction, this process repeats at a frequency of 2.5 Hz to 5 Hz, or between 18,000 and 36,000 vibrations per hour (vph). The industry standard for modern mechanical movements is currently between 21,600 and 28,800 vph, i.e., 3.5 and 4 Hz.
Since the balance wheel’s main task is to ensure that the watch runs precisely, its rate of oscillation needs to be fine-tuned. The watchmaker must therefore ensure that the oscillation is as even as possible and that the amplitude, i.e., the maximum deflection of the balance wheel, is neither too large nor too small. The corresponding adjustments are usually made using regulators, which are used to tweak the tension of the hairspring. Another option is to attach small weights to the balance rim to compensate for any imbalances.
To prevent the balance wheel from being knocked out of sync by harsh shocks and vibrations, it’s usually fitted with a shock protection system. However, this system still doesn’t guarantee 100% immunity, which is why watches with mechanical calibers are generally not suitable for most sports. If the balance spring is made of magnetic material, you’ll also need to steer clear of magnetic fields, which can wreak havoc on the watch.
Pros and Cons: Balance Wheel
- In use for 350 years
- Holds up forever with good maintenance
- Doesn’t need batteries
- Lends watches their distinctive ticking
- Showcases fine mechanical craftsmanship
- Usually not as accurate as quartz oscillators
- Higher maintenance
- Susceptible to shocks
- Power reserve is relatively low
- Can be susceptible to magnetic fields depending on material
Quartz Oscillator
In theory, the oscillating unit of a quartz watch is not much different from that of a mechanical watch. However, unlike the balance wheel, a quartz oscillator doesn’t have any mechanical components, consisting instead of a quartz crystal and small circuit. The battery takes over as the energy store, and a stepping motor acts as the escapement in watches with analog displays.
Once electrical voltage is applied to the quartz crystal, it begins to vibrate. This is because of the piezoelectric effect, discovered by Pierre and Jacques Curie in 1880. How fast the crystal vibrates depends on its size and shape; the quartz in wristwatches is only a few millimeters in size and usually shaped like a tuning fork. This ensures that the crystal vibrates at the industry standard of exactly 32.768 kHz, or 32,768 vibrations per second. The oscillation is read by the circuit and “translated” into a pulse – exactly one pulse per second. This in turn signals the stepping motor to move the second hand one pace further.
Thanks to the quartz oscillator’s significantly higher frequency, quartz watches are usually far more accurate than their mechanical counterparts. A quartz watch will only deviate by an average of 10 to 30 seconds per month, whereas some mechanical watches will deviate that much in a single day. That said, well-regulated mechanical movements are also capable of significantly better performance.
Quartz watches have another advantage in that they contain very few mechanical components, making them impervious to vibrations and magnetic fields and eliminating the nuisance of wear and tear. Choosing a quartz watch will also save you some trips to the watchmaker, as they won’t need to be sent for revisions every 3 to 5 years like mechanical watches do. Lastly, these timepieces don’t need to be supplied with new energy every few days to keep ticking; the wearer need only change out the battery every couple of years.
Despite these irrefutable advantages, quartz watches still don’t command much respect from watch enthusiasts. There are a lot of reasons for this consensus, but the most common argument is that quartz watches “lack a soul.” For most in the community, even the simplest mechanical movement is a more welcome sight than a quartz movement – a mechanical movement stands for craftsmanship, a quartz movement for machine-made, mass-produced goods. Of course, there are exceptions to the rule, such as Rolex’s Oysterquartz movements.
Pros and Cons: Quartz Oscillator
- Very high accuracy
- Strong resistance to shocks and magnetic fields
- Lower maintenance
- Long power reserve
- Bad reputation as mass-produced goods
- Needs batteries: harmful to the environment
- Low value retention
Other Oscillators
There have been many attempts to revolutionize the oscillator throughout watchmaking history. One of the most interesting inventions in the last few decades is the Spring Drive from Seiko. The engineers at the Japanese watch giant, which we can’t forget launched the first mass-produced quartz wristwatch, managed to combine the precision of the quartz crystal oscillator with the sex appeal of a mechanical movement.
Zenith have also been breaking new ground with the “Zenith Oscillator” introduced a few years ago. This oscillator has only one single component made of monocrystalline silicon that replaces both the balance wheel and the escapement. The oscillation frequency is 15 Hz, which makes the movements with this technology the most precise mechanical movements of all time, at least according to Zenith.
