Watch 101: Amplitude


Watch 101 - What is Amplitude

Watches are complicated things. For hundreds of years the making of watches has been as much an art form as a technical achievement. From torsion springs, to oscillators and balance wheels, the components that make up a watch can be – at best – confusing.

What is amplitude?

Amplitude is the measurement of the amount of rotation in the swing of the balance wheel, usually expressed in degrees.

The balance wheel is analogous to the pendulum in a pendulum clock and is used in mechanical watches as the timekeeping device. It is a weighted wheel that rotates back and forth and is returned to center position by a spiral torsion spring, the balance spring or a hairspring.

When the balance wheel swings, each swing is called a beat. Amplitude is the number of degrees of rotation of the beat. Amplitude is higher when a watch is lying flat or in the “dial up” or “dial down position.” Amplitude typically falls when the watch is in a vertical position, mostly because of increased friction. Amplitude that is too high or too low, or that changes to drastically in different positions, can indicate a problem with the movement.

What is a good amplitude number?

Typically a good amplitude number will fall between 270 – 300 degrees. For example, Rolex recommends no lower than 275 degrees.

If the degrees fall below 250, then your watch is running sub-optimally and if it falls below 230 degrees it will need to be serviced.

For more Watch 101 articles on Gracious Watch check out our article on Isochronism, the COSC, or our complete list of Watch 101 articles.