Automatic Watches
Amplitude in Mechanical Watches: What It Means for Accuracy
By Argos Watches
Mechanical watches are admired for their craftsmanship and for the way they measure time with only a few moving parts. At the heart of this process is the balance wheel, and how far it swings during its back-and-forth motion is a key sign of a watch's health. This important measure is called amplitude. Understanding it gives you valuable insight into how well a watch is running.
What Amplitude Means
In simple terms, amplitude is the amount of turn or swing the balance wheel makes. It shows how much energy the balance wheel is getting from the mainspring. A strong, steady swing shows that the watch is running well, while a change in the swing can be a sign of a problem.
The balance wheel and a tiny spring work together as the timekeeping heart of the watch. They control the speed at which all the gears turn. The amount of their swing, or amplitude, is very important.
A healthy amplitude for most modern watches is between 270 and 310 degrees when the watch is fully wound and lying flat. This range means the watch has enough energy to run well and keep good time, but not so much that it risks damaging its parts.
The balance wheel and a tiny spring work together as the timekeeping heart of the watch. They control the speed at which all the gears turn. The amount of their swing, or amplitude, is very important.
A healthy amplitude for most modern watches is between 270 and 310 degrees when the watch is fully wound and lying flat. This range means the watch has enough energy to run well and keep good time, but not so much that it risks damaging its parts.
Why Amplitude Is So Important
A watch with a good swing keeps time much better. This strong swing helps the balance wheel overcome minor issues like friction from old oil or the effects of gravity.
Low Amplitude: If the swing is consistently below 250 degrees, your watch may have a problem. A low swing can be caused by a few things:
Low Amplitude: If the swing is consistently below 250 degrees, your watch may have a problem. A low swing can be caused by a few things:
- Worn-out parts: Over time, the small parts that move inside the watch can get worn down. This adds extra resistance and makes it harder for the balance wheel to swing.
- Old oil: Mechanical watches need oil to run smoothly. When the oil gets old and dry, it can cause more friction, which lowers the swing.
- Weak mainspring: The mainspring is the power source of a watch. Over time, it can become weaker, which means it can't give the balance wheel enough power.
High Amplitude: If the swing is consistently too high, often above 310 degrees, it can also be a problem. This can cause the balance wheel to swing too far and hit its parts, which can damage them. This problem is known as "knocking."
High amplitude is usually a sign that something is wrong. For example, it could be caused by using a mainspring that is too strong or by using too much oil when the watch was serviced. If a watch's swing is too high, it should be checked by a professional.
High amplitude is usually a sign that something is wrong. For example, it could be caused by using a mainspring that is too strong or by using too much oil when the watch was serviced. If a watch's swing is too high, it should be checked by a professional.
How Watchmakers Check the Swing
You cannot judge a watch's swing just by looking at it. Watchmakers use a special machine called a timegrapher to check it. This machine listens to the watch's ticks and displays a lot of information about its performance, including the amplitude.
To get a correct reading, a watchmaker will:
To get a correct reading, a watchmaker will:
- Fully wind the watch: A watch must have full power to give the most accurate reading.
- Check in different positions: The watch's swing can change based on its position because of gravity. The watchmaker will test it while it is lying flat and while it is on its side.
- Find the right number: The watchmaker must enter a special number for the movement, called the lift angle, into the machine. This number helps the machine get a correct reading.
Other Factors and Brand Differences
A watch's swing is not a fixed number. It will be higher when the mainspring is fully wound and will slowly get lower as the watch runs. The swing can also change based on the type of movement. Some movements, like the Sellita SW300-1, have a lower ideal range (around 200-215 degrees) and still work well.
The beat rate, or how many times the balance wheel swings in an hour, is also connected to amplitude. Watches with a higher beat rate will often have a slightly lower amplitude but can still be very accurate.
Different watch brands have their own way of doing things. For example, Rolex movements are known for having a very high and steady amplitude because their parts are so well-made. Other brands like Patek Philippe have their own special parts to make sure the amplitude stays very consistent.
The beat rate, or how many times the balance wheel swings in an hour, is also connected to amplitude. Watches with a higher beat rate will often have a slightly lower amplitude but can still be very accurate.
Different watch brands have their own way of doing things. For example, Rolex movements are known for having a very high and steady amplitude because their parts are so well-made. Other brands like Patek Philippe have their own special parts to make sure the amplitude stays very consistent.
Conclusion
Amplitude is a precise measurement that reflects how efficiently a watch transfers stored energy from the mainspring to the balance wheel. Staying within the healthy range of 270–310° ensures reliable accuracy and reduces the risk of mechanical stress. Low amplitude indicates loss of power or excessive friction, while high amplitude signals potential over-swing and risk of damage.
By understanding amplitude, one gains not only a technical appreciation of how mechanical watches keep time but also a practical way of assessing their long-term condition. It remains one of the most important parameters in horology, bridging physics, engineering, and the craft of watchmaking.
By understanding amplitude, one gains not only a technical appreciation of how mechanical watches keep time but also a practical way of assessing their long-term condition. It remains one of the most important parameters in horology, bridging physics, engineering, and the craft of watchmaking.
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