Does a mechanical watch really define time?

High frequency and low frequency clocks

"We explain the difference"

The frequency is one of the most important properties of a mechanical watch movement and not only influences precision and power reserve, but also the wear and tear and robustness of the time indicator. But what exactly is the difference between high and low frequency calibers? We explain the concept of the beat rate, whether high frequencies really always mean better accuracy and why low frequency clocks can sometimes be beneficial.

Frequencies and semi-oscillations: the relationship

If you rummage through the product descriptions of hand-wound or automatic watches, you will always come across the indication of the half-oscillations per hour. What experienced collectors are more familiar with than tire pressure in a car often confronts new watch enthusiasts with the question of what exactly it means. The principle of semi-oscillations is easy to explain: they indicate how often the balance wheel moves back and forth per hour. Because every back and forth movement of the balance wheel is accompanied by a tick of the second hand, the number of beats per second is automatically determined. An example: If we are talking about 28,800 vibrations per hour, the second hand makes 28,800 ticks per hour - which corresponds to exactly 8 beats (= 28,800 / 3,600) per second. The higher the number of strokes, the smoother the movement of the pointer seems.

The frequency specification in Hertz (Hz) is just another form of representation and can be derived directly from the semi-oscillations of the clockwork. But be careful: Because Hertz numbers always reflect the amount of whole oscillations per second, they are by definition exactly half as large as the amount of half oscillations. 8 beats per second correspond to 4 Hz. Other common specifications are 2.5 Hz, 3 Hz and 5 Hz, which correspond to 18,000, 21,600 and 36,000 vibrations per hour. One would intuitively assume that the precision of the caliber increases with the number of strokes - after all, quartz watches tick with unbelievable frequencies of over 30,000 Hz and are known to be much more accurate than mechanical time indicators.

Does the precision really increase with the number of strokes?

If we look at prominent examples of high-frequency clocks such as Zenith's El Primero or Seiko's Hi-Beat models with 5 Hz, intuition seems to be confirmed: What beats faster is also more precise. The real connection, however, is more complex and revolves around the constancy of the beat number, i.e. the question of how evenly the clockwork beats. Even the fastest balance wheel is useless if its Hertz number cannot be kept constant over time. Stationary pendulum clocks, on the other hand, as they were previously used in scientific laboratories, had extremely low frequencies of 0.5 Hz and were more precise than any modern wristwatch. On the wrist, however, the balance wheel is constantly subject to movement, which brings the time indicator a little out of step with every push.

Only this logic explains why high-frequency clocks are usually more precise: They can compensate for all the small movements and jolts of everyday life more quickly than low-frequency clocks, so they get out of step for a shorter period of time and thus create a smaller rate deviation overall Day. So far so good. But if high-frequency watches are apparently superior, why are there calibres with a deliberately lower beat rate at all?

More power reserve, less maintenance: low-frequency watches have an advantage

Because precision is by no means the only criterion for a good watch. The power reserve, for example, is very important: Nobody wants a time indicator that runs out of power after a night or a few hours. If you were to keep increasing the number of strokes, that would be exactly the consequence. Many beats consume a lot of energy, which is why high-frequency watches either have to be upgraded with special measures such as larger barrels or simply a lower endurance is accepted.

In addition, there is faster wear and tear and higher maintenance costs with rapidly oscillating calibers. While the frequent interactions between the armature and escape wheel cause accelerated wear of the components, lubricating oils often cannot cope with the high speed and are literally thrown away. Special lubricants, but also separate materials in the clockwork, are required to remedy these problems. At the same time, in contrast to low-frequency versions, high-frequency balance wheels have a smaller diameter, which makes manual adjustment by the watchmaker more difficult.

How can chronographs measure hundredths of a second?

This makes it clear that the higher precision of high-frequency calibres is by no means given, but has to be paid for with great effort. The frequency is even more important for chronographs than for classic time indicators, because the number of strokes acts here as a natural limitation of the time stopper. Without expert knowledge, it becomes clear that a watch with 28,800 vibrations per hour (4 Hz) can measure with a maximum of eighths of a second because its second hand makes 8 ticks per second. A Zenith El Primero Chronograph with 36,000 vibrations per hour (5 Hz) can therefore stop intervals with an accuracy of tenths of a second. But how is it possible that models like the ZenithDefy 21 can measure accurately to a hundredth of a second?

The answer is obvious: with a beating rate of 50 Hz. In order to be able to achieve rapid frequencies like this without a significant loss of power reserve, the Swiss brand - like TAG Heuer - uses an intelligent design with two separate movements. A normal 5 Hz caliber is responsible for the time display, while the time stopping is taken over by a 50 Hz caliber. Although this movement only runs for barely an hour when fully wound, its performance of one hundred (!) Beats per second is impressive. And it demonstrates another, difficult to measure advantage of high-frequency calibers: their fascination. “Higher, faster, further” - what drives the Olympic Games, fast swingers represent in the world of watches. Low-frequency clocks find it difficult to keep up.

Frequency specification in HertzFrequencies and half-oscillationsSpeed ​​deviationPower reserveHigh-frequency and low-frequency mechanical watch movementPrecisionBeat numberZenith El Primero Chronograph2020-07-31