Ultraprecise Eco-Drive movementCalibre 0100


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The challenge:
Accurate to ± 1 second

CITIZEN has pursued the essence and further possibilities of the watch ever since the company’s founding. There is one challenge that we have actively confronted throughout that entire time: superior precision.
In 1924, we developed our first pocket watch, the “CITIZEN.”
We debuted our first quartz watch accurate to ± 10 seconds per month in 1973, and in 1975, we debuted Crystron Mega, the world’s first quartz watch accurate to ± 3 seconds per year.
We continued to produce even more accurate watches with longer running times incorporating our proprietary light-powered technology Eco-Drive.
This year, as we mark our 100th anniversary, we have achieved yet another milestone: Calibre 0100, an Eco-Drive movement with annual accuracy ± 1 second, which tells the world’s most precise time.*
Calibre 0100 tells the precise time autonomously based on an internal mechanism with no reliance on time signals from radio towers or GPS satellites.
It marks the individual seconds in their purest and most refined form.
Like a strong person who achieves his goals through sheer force of will, it uses its own rhythm to tell the precise time for everyone, wherever they are, without depending on anything outside itself.
The Calibre 0100 marks the start of the next one hundred years of watchmaking for CITIZEN.

*As of February 2018, for an analogue light-powered watch, according to research by Citizen Watch Co., Ltd.
This is a concept model and will not be released for sale.

FEATURESTechnology for ultraprecision

Small deviations can become big deviations

Quartz watches tell the time, second by individual second, by taking advantage of the characteristic way that crystals oscillate at a fixed cycle when voltage is applied to them. The crystal oscillator is really at the heart of quartz watches. It is what governs their precision.
Although quartz watches are very precise compared to mechanical watches, small errors can creep in when external factors such as temperature and gravity start to influence the crystal oscillator and produce changes in frequency. For the standard quartz watch, this represents only the tiniest of deviations. When, however, you are dealing with an ultraprecise watch accurate to ± 1 second per year, that is actually a major deviation. Calling on the technological know-how and experience built up over the past 100 years, CITIZEN came up with a solution to every single deviation-causing issue.

Reinvention, starting
with the oscillator

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The first thing we did was to rethink the crystal oscillator itself. We decided to use an AT cut crystal oscillator in place of the tuning fork-shaped crystal oscillator commonly found in most quartz watches.

Srandard tuning fork-shaped(or XY)cut AT cut crystal oscillator

We selected the AT cut crystal oscillator for two reasons. First, it is little affected by changes in temperature. Crystal’s thermal characteristics vary depending on the angle at which it is cut from the source crystal. Compared to the standard tuning fork-shaped (or XY) cut, the AT cut has excellent thermal stability at normal temperature levels (diagram 1).

1. Relationship of cutting orientation
and thermal characteristics

Relationship of cutting orientation and thermal characteristics

Reinvention, starting
with the oscillator

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Second, it is not much affected by changes in spatial orientation either. The gravitational acceleration that results from changes in wearer posture and sweeping arm movements is fatal to precision. Because the traditional tuning fork-shaped crystal oscillator makes quite sizeable oscillations in empty space, just changing the position of a watch is enough to create deviations. By comparison, the oscillations of the AT cut crystal oscillator are tiny. This makes it possible to minimise the impact of spatial orientation and position (diagram 2).

2. Deviations resulting from changes in position

Deviations resulting from changes in position

AT cut crystal oscillators are normally used in large precision instruments such as personal computers rather than for watch movements. We there fore utilised our internal resources, reviewing everything from the choice of materials and design through to final settings en route to developing a proprietary AT cut crystal oscillator specifically for a watch movement. It's no exaggeration to say that we succeeded in creating the Calibre 0100 because CITIZEN is a manufacture d'horlogerie.


Evolving systems for
greater precision

For the Calibre 0100, we also applied our in-house technology to the integrated circuit that functions as the brain of the quartz watch. CITIZEN’s existing precise watches accurate to ± 5 seconds per year feature a function that monitors the temperature once per minute and adjusts the frequency of the oscillator accordingly. We further raised the precision of this function by doubling the number of points we temperature test in the crystal oscillator prior to the completion of each watch. As a result, we could preset the correction system with more realistic approximate values and could correct deviations with greater precision.

Evolving systems for greater precision

We also added functions such as the shock counteraction function, which instantly locks the rotor before restarting the hand whenever the watch gets a shock, and the automatic hand correction function, which checks the position of the hands at regular intervals and restores them to the correct position in the event of any deviation. We have created ultraprecise watches that continue telling the precise time even in the most difficult circumstances.

Shock counteraction functionHow it works

Shock counteraction function How it works

To keep running with

The traditional tuning fork-shaped crystal oscillator has a frequency of 32.768 kilohertz. By contrast, the AT cut crystal oscillator oscillates at 8.4 megahertz—a frequency 256 times higher. The AT cut crystal oscillator thus consumes a lot of electricity even before having to drive the temperature correction and shock counteraction functions. It was essential for us to reduce energy consumption wherever possible in order to maximise the running time of Eco-Drive, CITIZEN’sproprietary light-powered technology.

As well as developing a proprietary oscillatory circuit that can run at low voltage, we aggressively lowered the quantity of energy consumed by every part of the movement. We succeeded in raising Eco-Drive’s running time so that it kept running as long as there is light, and even run in complete darkness for up to six months on a single full charge.
The Calibre 0100 combines both precision and a long running time. This is one of the possibilities of the watch that CITIZEN has realised in its pursuit of the essence of the watch over the last 100 years. We did so because we are a pioneer of light-powered watch and continue to advance the technology even today.


A future where a purer form of time is shared by all

By optimising every possible element, we develop watches that mark the individual seconds in their purest form. That is what pursuing the essence of the watch means to us. And that is our mission as a watch company. The ultraprecise Eco-Drive movement Calibre 0100 is a self-reliant timepiece. From the moment it leaves our factory, it continues to tell the precise time with no dependence on any outside sources. As each ultraprecision CITIZEN watch with Calibre 0100 goes forth into the world, a new future begins—a future where everyone, everywhere gets to share in time in its purest and most refined form.