De Bethune Introduces The Sensorial Chronometry Project

Written by Jack Forster

A sensor-loaded “lab watch” is the first step to customized mechanical chronometry.

One of the great classic problems in watchmaking is the fact that a watch will run at slightly different rates, depending on its position relative to the pull of gravity. The tourbillon was an attempt by Breguet to address this, but in most instances, watches are adjusted so that the difference between rates is kept as low as possible. However, the timing of the rate of a watch in different positions is usually conducted statically, and timing machines produce an instantaneous measurement of rate, rather than variation in rate over time. The COSC (Contr?le officiel suisse des Chronomètres) the independent body which certifies chronometers, measures variations in rate between positions, as well as average daily rate and mean variation in rates and the testing is fairly rigorous – a movement tested and certified as a chronometer has passed a fifteen day battery of tests and is guaranteed to perform to within -4/+6 seconds per day.

However, watchmaking is nothing if not the pursuit of perfection, and better precision is even today a subject of active research. The fundamental problem with tests such as the ones performed by the COSC (and by watch brands which do not submit movements to the COSC, as well, which use the same basic procedures) is that the testing processes are, necessarily, standardized across the entire range of movements tested. The movements may, depending on the actual habits of a particular user, perform within the certified range but at the extremes of owner behavior – extremely active, versus almost entirely sedentary – you may tend to see daily variations in rate at corresponding extremes of performance. The solution to this problem is to have a watch adjusted after a period of wear, if the owner wants better precision and accuracy, but for this to be effective, the owner has to closely observe the performance of the watch, with a level of vigilance few if any actual owners will have.

Ideally, to adjust a watch precisely to the habits of a given owner, you’d want to gather data almost continuously, and over a long enough period of time for the information to be a statistically significant sample of the owner’s general habits – just measuring one day won’t cut it if the wearer is an avid weekend golfer, for instance. To address this problem, De Bethune’s cofounder Denis Flageollet has come up with something really different.

The Sensorial Chronometry project is a new way to evaluate a client’s physical habits and adjust a watch specifically to their lifestyle, even before the watch is worn for the first time. The heart of the system is something De Bethune’s never made before: an electronic watch, loaded with sensors for keeping track of the owner’s movements. Other sensors in the “laboratory” watch measure relative humidity, temperature, ambient magnetic fields, and atmospheric pressure (believe it or not, barometric pressure does influence the rate of watch as air resistance to the movement of the balance changes depending on altitude, although the effect is very small and usually swamped by other factors, like variations in position, and temperature). A gyroscopic sensor captures changes in direction.

The sensors can capture a very wide range of data. The accelerometers can measure forces from two to 400g, and the magnetism sensors can measure fields as low as 200 gauss and as high as 2000 gauss.

The laboratory watch is large but very light in the hand and on the wrist, and for the collector interested in the pursuit of precision for its own sake, and as something of an art form, wearing the lab watch for a couple of weeks isn’t a bug, it’s a feature. I should mention by the way that the lab watch is not meant to be worn while swimming however, on the off chance you do want to swim with your custom adjusted De Bethune timepiece, the company will provide a water resistant outer case.

The sheer number of individual measurements is rather staggering. There are three overall recording modes – two of these are for lab calibration use and involve only a single sensor. “Temporal recording mode” is what owners will be using while wearing the laboratory watch. Data points for all sensors together work out to about 80 measurements per second per sensor, and at typical sensor settings, two?million?data points are captured per hour.?

Because data capture happens almost constantly the level of resolution is much better than you could ever possibly get from just checking the watch a few times a day. That data is then used by De Bethune to make fine adjustments to the watch prior to its leaving the?manufacture?in l’Auberson, and before the watch leaves De Bethune it’s tested on a robotic arm, programmed to simulate the movements of the specific owner of that specific watch.

So what exactly does “adjusting” a watch mean? Generally, it means making very specific and very minute changes to the balance and balance spring. The position of the inner and outer attachment points for the balance spring, as well as the shape and thickness of the balance pivots and the care with which the balance is poised, are all factors.

These adjustments are distinct from regulating the watch, which usually involves changing the effective length of the balance spring. Regulating is a fairly straightforward procedure – generally it just involves moving the balance spring regulator’s position – but fine adjustment is not. The best watches traditionally had the words, “Adjusted to isochrononism, temperature, and 5 positions” engraved on the movement bridge but the testing procedures today still rely on measurements of mean performance and static positions. Dynamic measurements of owner behavior and dynamic testing of the completed and adjusted watch should provide better precision.?

Needless to say, this is a highly time and labor intensive process. The Sensorial Chronometry project will involve a very small number of watches at the outset, when it launches in 2023, and will at launch be offered for just one watch – the De Bethune DB28 GS. Registration for chronometry testing will be in early 2023 and De Bethune expects to start delivery at the end of that year.?

During our introduction to the project at the De Bethune?manufacture,?Watchbox’s Tim Mosso pointed out that there is nothing a hardcore collector loves more than a service watch and that there was therefore a non-zero chance that folks signing up for a Sensorial Chronometry-adjusted watch would want to keep the lab watch, one way or another. However De Bethune does not, currently, plan to include the lab watches as part of the package, as there will be very few of them and the cost of research and development was considerable. As we all know though, there is nothing that makes a serious collector want something more than to be told they cannot have it and I suspect that there will those among De Bethune’s fans who would spare no trouble nor additional expense to add one of the lab watches to their collection, along with the actual custom-adjusted watch.

This level of highly customized watchmaking is obviously not for everyone, but it certainly?is?possibly for anyone interested in De Bethune in general and extremely cutting edge chronometry in particular. There is no other individual watchmaker or brand capable of offering this service since it relies on very specific measuring and testing devices. But the Sensorial Chronometry project is on a continuum with De Bethune’s constant experimentation with the fundamentals of watchmaking and of precision timekeeping, and with the company’s commitment to small batch, very high touch watchmaking – an adventure in precision whose vehicle, the DB28 GS, is an extremely beautiful watch.

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