What exactly is a Quartz Watch?

How do quartz watches achieve such remarkable accuracy? In a broader sense, what is a quartz watch? Learn why quartz is considered such a reliable timekeeper.

In the 1970s, the 'quartz watch' emerged as the latest technological innovation. These watches initially featured red LED displays and were priced at approximately $500 in the United States. Over time, quartz watches have evolved to feature either LCD or traditional mechanical timekeeping (hour and minute hands), and their cost has significantly decreased.

It's not unusual to find quartz watches given away as free gifts in cereal boxes! You might also come across quartz.htm">rose quartz, the lovely pink variety, in affordable crystals and beauty rollers at the supermarket.

Have you ever wondered why it's called a quartz watch? Or why a quartz clock is so much more accurate than a wind-up one? In this edition of Mytour, you'll uncover the fascinating electronic process behind the quartz crystal and how it powers a quartz watch!

Before Quartz Movements

The wind-up watch is a remarkable piece of technology in its own right! It's the result of centuries of research and development, dating back to the late 14th century [source: Galanti]. Over time, various innovations have made mechanical watches smaller, thinner, more reliable, more precise, and even self-winding!

The parts found in modern wind-up watches have been in use for hundreds of years:

Check out How Pendulum Clocks Work for a detailed explanation of these different components.

By the late 1960s, the Bulova watch company took its first step away from the oscillating balance wheel — they introduced a transistor oscillator that powered a tuning fork [source: Bulova]. This watch emitted a hum at hundreds of hertz (Hz, cycles per second) rather than ticking! Gears still converted the mechanical movement of the tuning fork to move the hands, marking two significant advances:

In the late 1960s, a watchmaking company was bound to seek the next step — a technology that would provide even more precise timekeeping than the tuning fork. Integrated circuits were new, but their costs were rapidly decreasing, and the number of transistors was increasing.

LEDs were also emerging at the time. However, there were still a couple of challenges to overcome: finding a new timing mechanism and developing an integrated circuit that would consume minimal power to enable the watch to operate on a small internal battery.

Quartz Technology

Selecting a timing element was not an issue. The quartz crystal is possibly thousands of times more precise than the tuning fork, and quartz crystals had been used for years. The only decision was about the type and frequency of the crystal. The challenge lay in choosing the integrated circuit technology that would operate with minimal power consumption.

Quartz crystals have been widely used for many years to provide accurate frequencies for all radio transmitters, receivers, and computers. Their precision comes from a remarkable set of factors: Quartz, which is silicon dioxide (similar to most sand), is resistant to most solvents and stays crystalline even at high temperatures.

What makes it an electronic marvel is the fact that when quartz is compressed or bent, it generates a charge or voltage on its surface. This is a common phenomenon known as the Piezoelectric effect. Similarly, if a voltage is applied, quartz will bend or change shape slightly.

If a bell were carved from a single quartz crystal, it would continue to ring for minutes after being struck. Almost no energy would be lost in the material. A quartz bell, when shaped correctly according to its crystalline axis, would produce an oscillating voltage on its surface. The oscillation rate remains stable despite temperature changes. If the voltage is extracted using plated electrodes and amplified by a transistor or integrated circuit, it can be fed back into the bell, keeping it ringing.

A quartz bell is possible to create, but it’s not the ideal shape since too much energy is transferred to the air. The most efficient shapes are a straight bar or a disk. A bar has the advantage of maintaining a consistent frequency as long as the length-to-width ratio stays constant.

A quartz bar can be extremely small and oscillate at a relatively low frequency — typically 32 kilohertz (KHz) is chosen for watches. This frequency not only suits the size but also reduces power consumption, as circuits that divide the crystal’s frequency down to the required pulse rate for display use more power at higher frequencies. Power consumption was a major challenge in early watches, and the Swiss invested millions in advancing integrated-circuit technology to reduce the 1 to 2 MHz frequencies generated by the more stable disk crystals.

Today’s quartz timepieces use low-frequency bar or tuning-fork-shaped crystals. These crystals are often crafted from thin quartz sheets that are plated like an integrated circuit and chemically etched into the desired shape.

The key factor that differentiates precise timekeeping from less accurate watches is the initial frequency accuracy and the precision of the quartz sheet's cut angle relative to the crystalline axis. The level of contamination allowed to reach the crystal’s surface inside the watch can also impact its accuracy.

The electronics in a quartz movement first amplify noise at the crystal's frequency. This noise gradually builds up and regenerates into an oscillation, effectively starting the crystal to ring. The output from the quartz oscillator is then transformed into pulses that are appropriate for digital circuits.

These circuits divide the crystal’s frequency and then convert it into a format suitable for the display. (For more details, see How Digital Clocks Work on dividers and display drivers.) In a quartz watch with hands, the dividers generate one-second pulses that power a tiny electric motor, which is connected to standard gears to move the hands.

Always on Time

A quartz watch is a true marvel of precision, affordability, and durability that has revolutionized the watchmaking industry since it first appeared. By using the reliable oscillations of a quartz crystal to measure time, quartz movements deliver exceptional accuracy, especially when compared to mechanical watches.

Thanks to their reliance on battery power and the minimal number of moving parts, quartz watches are more dependable over time and require less maintenance. As technology progresses, quartz watches continue to exemplify the innovative spirit of watchmaking, blending the timeless elegance of traditional timepieces with the efficiency and precision of modern electronics.

About the Author

Douglas Dwyer is the founder of Frequency Precision Ltd, offering consulting and design expertise to the global electronics sector. His journey in frequency control began in the 1960s, and since then, he has written extensively on topics such as crystal oscillators, temperature-compensated crystal oscillators, oven-controlled crystal oscillators, surface acoustic wave oscillators, and industrial quartz crystal fabrication technologies. His fascination with the history of clocks and watches dates back to his work in the development of quartz timepieces.