Amplitude
Amplitude is how far the balance wheel rotates from its rest position to the peak of its swing in a mechanical watch, measured in degrees and read on a timing machine. A healthy figure shows the movement is getting good energy, while low amplitude points to a tired mainspring, gummed-up oil, or a service that is due.
At a glance
- Unit
- Degrees
- How it is read
- Timing machine (timegrapher)
- Healthy range
- Roughly 270 to 310 degrees dial-up
Amplitude is one of the most telling signs of a mechanical watch's health. With each swing, the balance wheel rotates away from its rest position to the peak of its travel, and the angle of that swing is measured in degrees. A watchmaker reads it on a timing machine, commonly called a timegrapher.
What a healthy figure looks like
Amplitude is usually judged on a fully wound watch in the dial-up position:
- Good range: roughly 270 to 310 degrees dial-up is generally considered healthy
- Position effect: the figure drops somewhat in vertical positions, which is normal
- Low amplitude: a clearly low reading is usually a warning sign
The figure depends on how cleanly energy passes between the balance wheel and the escapement, and it is read alongside other measures such as beat rate and beat error.
What low amplitude tells you
A low reading often means a tired mainspring, oil that has dried or gummed up, or wear in the parts, and it signals that a service is due. Browse our movement category for related terms, and read our guide on how to care for a mechanical watch to keep yours running well.
Examples
When a fully wound mechanical watch reads around 290 degrees dial-up on a timegrapher, the movement can be considered to be running in good health.
View this watchIf that same watch has dropped to around 190 degrees months later, it often points to dried oil or a service coming due.
Comparison
Amplitude reflects the energy health of the movement, while beat rate sets its timekeeping pace; the two measure different things.
| Option A | Option B | Notes |
|---|---|---|
| Amplitude | Beat rate | Amplitude gives the swing angle of the balance in degrees; beat rate gives how many beats occur per second. |
Related terms
Watches that show this
Frequently asked questions
What is a healthy amplitude figure?
On a fully wound watch in the dial-up position, roughly 270 to 310 degrees is generally considered healthy. The figure drops somewhat in vertical positions, which is normal, while a clearly low reading is usually a warning sign.
What does low amplitude indicate?
Low amplitude often means a tired mainspring, oil that has dried or gummed up, or wear in the parts. It is a strong sign that the movement is no longer passing enough energy and that a service is due.
How is amplitude measured?
Amplitude is measured with a timing machine, also called a timegrapher. The device listens to the sound of the balance wheel and calculates the swing angle in degrees, giving a read on the movement's health without opening the watch.