Automatic or Quartz Watch? How the Movements Work

The difference between an automatic watch and a quartz watch is what drives and regulates it. In an automatic watch a rotor winds a spring as you move your wrist, and an oscillating balance divides up the time. In a quartz watch a battery supplies current to a quartz crystal that in most watches vibrates 32,768 times a second, and a circuit and a tiny stepper motor move the hands. The quartz watch is more accurate; the automatic manages without a battery.

Facts

Power and beat

Every timepiece consists of two parts: something that provides power and something that keeps the beat. The power comes from a weight, a spring or a battery. The beat comes from the escapement, which divides time into equal steps. In a longcase clock it is the pendulum, in mechanical wristwatches an oscillating balance with a hair-fine hairspring, and in the quartz watch a crystal. The movement diagram further down shows three escapements in motion, from the medieval verge to the quartz watch.

The pendulum, which Christiaan Huygens put in a clock in 1657, made clocks reliable to within a minute a day, as in Huygens’s pendulum clock. The balance spring of the 1670s made it possible to carry an accurate timepiece, and the wristwatch inherited that technology. The word quartz watch is explained in the glossary.

The mechanical and the automatic watch

In a mechanical watch a coiled mainspring drives the wheels. The escapement lets the wheels advance a small step at a time, in time with the swings of the balance, and that is heard as the watch’s ticking. A hand-wound watch is wound with the crown, often once a day.

An automatic watch also has a rotor, a semicircular weight that swings freely as the wrist moves and winds the spring. The Englishman John Harwood patented an automatic wristwatch in the 1920s, and in 1931 Rolex patented a rotor that swung in both directions in the Oyster Perpetual. It was housed under a domed back, which gave the Bubbleback its name. After the Second World War automatic movements became common, in everything from diver’s watches such as the Submariner to cheap watches such as the Seiko 5. An automatic watch that has lain still will stop after a while and must be wound or shaken into motion.

The quartz watch

Quartz has the property of flexing when current is applied, and a tiny quartz crystal shaped like a tuning fork then vibrates at a very even rate. In most quartz watches the rate is 32,768 vibrations a second. A circuit halves the number fifteen times until it becomes a pulse once a second, and the pulse turns a stepper motor that drives the hands. The error is a few seconds a month, against a few seconds a day for a good mechanical watch.

The Seiko Astron, on sale from Christmas Day 1969, was the first quartz wristwatch and cost as much as a car. Within ten years quartz watches became cheap, and digital watches with LEDs and then liquid crystals came in the Space Age. Watches such as the Casio F-91W and the G-Shock made accuracy almost free.

How to tell the difference

Look at the seconds hand. In most quartz watches it jumps one step a second; in a mechanical watch it glides forward in many small steps a second, so that the movement looks smooth. Turn the watch over: a small cover or a screw-down lid for the battery suggests quartz, and a glass case back often shows a mechanical movement with a rotor. The text on the dial helps too, such as Automatic, Perpetual or Quartz.

An automatic watch that has stopped will often start again if you shake it gently; a quartz watch with a flat battery will not. Quartz watches are often lighter and thinner. The detail drawings below show the battery cover and the plastic case that characterise the age of the quartz watch. To work out how old a watch is, see the guide to dating a wristwatch.

Intermediate forms

Between the mechanical watch and the quartz watch there are several intermediate forms. In the 1950s and 60s came electric wristwatches, such as Hamilton’s Electric and Bulova’s Accutron, in which a tuning fork regulated the movement and foreshadowed the quartz watch. Later came quartz watches driven by a rotor that charges a capacitor, and quartz watches with solar cells that never need a new battery.

Radio-controlled watches set themselves from a time signal, and smartwatches, such as the Apple Watch from 2015, have made the wrist a screen. Meanwhile the mechanical watch has gained a new role as craft and collector’s item, and many makes have reissued their classic models.

The quartz crisis and the two watches today

The quartz watch turned the watch industry upside down. In the 1970s Japan’s Seiko, Citizen and Casio took over the market, and the Swiss watch industry lost two thirds of its jobs. Salvation came with the Swatch from 1983, a cheap plastic quartz watch with few parts, sold as fashion in the age of Postmodernism, and with a new interest in mechanical watches. Read more in the guides to the Seiko Astron and the quartz crisis, the Swatch and the Casio F-91W.

Today the two live side by side. The quartz watch is more accurate, cheaper and needs only a new battery every two or five years; the mechanical one needs servicing every few years but can run for generations. Many choose mechanical for the craftsmanship and the sound, as in the guide to the Rolex Submariner. The page on watches and clocks has the history of timekeeping in chronological order.

How to recognise it

Exercise

What winds the spring in an automatic wristwatch?