Most people have heard of a quartz watch, but few fully understand what the designation means. The name refers to an actual quartz crystal that is sitting inside their watch, with the unique crystalline structure of the stone acting as the perfect material for the piezoelectric oscillator in wristwatches. Initially, this technology was not widely adopted. It was not until many years later when the cost of quartz became commercially viable.
In 1927, Warren Marrison and J. W. Horton created the world’s first quartz clock. It wasn’t until 1969, however, that the technology was effectively miniaturized for use within a wristwatch by Seiko, whose inaugural quartz model Astron paved the way for an electric generation.
As mass production grew and retail prices dropped, the popularity of quartz watches soon overtook the more traditional mechanical alternatives. This peaked in the 1970s, a period referred to as the "Quartz Crisis" by more traditional watchmakers in Switzerland and the "Quartz Revolution" in the USA and Asia.
Since the beginning of the watchmaking industry, artisans have worked to improve the isochronism of watches. Having good isochronism means the watch keeps time consistently across a variety of positions and temperatures. Quartz allowed watch development to take a big leap forward in this area because it is highly inert, and relatively resistant to material fluctuations (although not entirely impervious).
At the heart of this breakthrough is researchers' discovery that quartz crystals could be made to oscillate at an incredibly stable rate when an electric current was passed through them and that it then emitted a small voltage of its own as a response. When electricity is passed through properly cut and formed quartz it vibrates 32,768 times per second. Scientists can then create an integrated circuit, which is able to “listen” to the crystal and count the oscillations via the piezoelectric output of the crystal. That information and energy can be used to send a message and impulse to the hands or display of a quartz watch that it is time to move.
For the quartz to vibrate at the correct frequency, it must be cut into a tuning fork shape along a particular crystal plane (imagine splitting wood along the grain). Cutting the crystal along the correct crystal plane also helps minimize the crystal’s susceptibility to temperature, which although minimal, is still a concern for all crystal oscillators. Manufacturers of quartz watches came up with a simple fix for maintaining the constant temperature of the crystals by simply advising owners to wear their watch regularly, which naturally maintains the optimal temperature. The result is a deviation in the timekeeping of a quartz watch around ±0.5 seconds.
There are, however, even further steps that can be taken to reduce the effect of temperature on the performance of quartz timepieces. It is possible for the very finest quartz-controlled movements to accurately measure their temperature and make adjustments to compensate for fluctuations. Thermal compensation mechanisms are used in the highest-end quartz calibers to help their movements achieve the minimum standard for chronometer certification.
A chronometer is a superlative timekeeper as adjudged by an independent testing body. The most common testing body is COSC (Contrôle Officiel Suisse des Chronomètres). The COSC requirements for quartz chronometers demand that the average daily rate standard is ±25.55 seconds per year. Movements using a thermocompensator can achieve accuracies to within ±5 to ±25 seconds per year.
Research into quartz technology is still ongoing. In 2018, Citizen released the caliber 0100 Eco-Drive at the Baselworld show in Switzerland. Caliber 0100 is supposedly accurate to ±1 second per year, an incredible technological feat. These refinements have been made by adjusting the cut of the quartz crystal, upping its vibrations to 8,388,608 vibrates per second, and using a thermocompensator. While this technology is currently price prohibitive for many (the Citizen 0100 starts at $7,400), its exploration and refinement could lead to it becoming accessible more broadly in the near future.