Watches are more than accessories; they are complex machines that contain hundreds of components put together to achieve the ultimate objective of maintaining time correctly. Perhaps one of the most crucial parts of the mechanical watch is the balance wheel, which moves back and forth driving the accuracy of the watch.
The extent of travel of a balance wheel is formally known as amplitude. In this blog post, we will take an in-depth look at the concept of amplitude, especially the ideal range of 270 - 310 degrees, what it means for your watch and why it’s important that you keep your timepiece in tune.
Buenos Aires Theorema | GM-114-12 | Gold.
What Does Amplitude Mean on a Watch?
Amplitude basically describes the degree of rotation in the balance wheel when a mechanical watch is in oscillation. This illustrates the amount of energy that is being relayed from the mainspring to the balance wheel and is shown in terms of degrees. In other words, the amplitude is the amount of travel the balance wheel undergoes during one swing and shows the state of health of the mechanics of the watch.
The higher the amplitude, the more energy the balance wheel receives, and the wider the arc of oscillation it makes. At the same time, a low amplitude indicates an underpowered movement struggling to receive enough energy. On most modern wristwatches, the preferred amplitude range lies between 270 and 310 degrees for ideal operating efficiency.
However, amplitude is not a fixed number. In real life, it could show so much variance depending on many factors, including the watch’s position, the amount of residual power in the mainspring, or even the condition of the movement. The amplitude of a mechanical watch can be monitored to ascertain the timepiece’s health over time or to determine when it needs servicing.
Why Amplitude Matters
Amplitude is one of the most critical indications of the energy transmission inside your watch's movement. A mechanical watch depends upon the stored energy in the mainspring that is used to energize the balance wheel. So basically, the amplitude is a reflection of how efficiently that energy is transferred through the movement.
The amplitude should fall in the healthy range of 270-310 degrees, indicating that the balance wheel is swinging with enough energy to keep accurate time. If the amplitude is too low, it signifies that the balance wheel is not obtaining enough energy, leading to inconsistent timekeeping or the watch stopping altogether.
On the contrary, an amplitude that is too high can cause problems like knocking, which can damage the internal components of the movement.
For owners who take pride in their mechanical watches, regularly checking the amplitude is the best way to monitor the condition of the movement and nip issues in the bud before they worsen.
Multifunction timegrapher.
How Is Amplitude Measured?
Amplitude is measured using a specialized device called a timegrapher. A timegrapher is a machine that records various data points about a watch's movement, including the beat rate, beat error, and of course the amplitude.
Here are the steps needed to measure your watch’s amplitude:
First things first, wind the watch:Before testing, you must wind your mechanical watch. A fully wound mainspring ensures that at any given time, maximum power is being supplied to the movement. Thus, you will get an accurate reading of the amplitude.
Setting the watch in different positions:Because amplitude can be different depending on the position of the watch, testing should be done in several positions. Commonly, the amplitude is higher when the watch is horizontal (dial-up) and lower when it is vertical, crown up, or crown down. Such a difference is normal and sometimes can serve as an additional source of information about the health of the movement.
Find the correct lift angle:Inputting the correct lift angle is critical for the timegrapher to accurately obtain the amplitude reading. The lift angle is the amount of angle the balance wheel travels when it is in contact with the pallet fork.
Most modern watches have a lift angle of 52 degrees, but this may vary depending on the nature of the movement in question. If the lift angle is set into the timegrapher incorrectly, then the amplitude reading will be incorrect.
Processing the results:Once the watch has been placed on the timegrapher, the machine will give an amplitude reading, among other metrics. Provided the amplitude falls within the range of 270 to 310 degrees, then your watch is said to be running in good health. If the amplitude does not fall within this range, further tests may need to be conducted to verify the cause of this mismatch.
The best amplitude rangeis between 270 and 310 degrees (measured when the movement is fully wound and the watch is lying flat). Watches operating within this range are in very good condition since it means that the balance wheel is getting enough energy to retain consistent timekeeping.
A balance wheel with an amplitude within this range guarantees the stability of the watch's movement and makes it less sensitive to various external influences, such as changes in temperature or physical shocks.
That being said, sometimes what accounts for the exact ideal range will vary depending on the movement. For example, some movements, such as the Sellita SW300-1, have acceptable amplitude ranges as low as 200-215 degrees, which can be considered normal for that caliber. However, most modern watches need a 270-310-degree amplitude to ensure a properly functioning movement.
Tufina Laboratories: Measuring the amplitude of Damascus Theorema T3008-4.
What Does a Low Amplitude Indicate?
If the amplitude is low, usually below 250 degrees, your watch may have a problem with the movement. Normally, a low amplitude could be triggered by several reasons.
Worn-out parts:The escapement or the gear train may wear out after a certain period of time, adding extra resistance to the movement that decelerates the balance wheel. As a result, we get a lower amplitude, in which case you may need to service your watch or replace its worn-out parts.
Grease issues:Mechanical watches require greasing to reduce friction within their moving parts. When the oils inside the movement become old and deteriorate, they are not able to perform as they should. This causes increased friction, resulting in lower amplitude. Watches with old, dried-out greases will have to be serviced and re-oiled in order to improve their amplitude.
Weak mainspring:The mainspring is considered the powerhouse in any mechanical watch. It stores energy and then releases it progressively to turn the movement. Over time, this spring can get weaker, leading to lower amplitude readings. In such cases, you would need to replace the mainspring in order to restore the movement’s performance.
A low amplitude can cause the watch to lose time or even stop, since the balance wheel would lack adequate momentum to overcome outside influences, such as shocks or changes in position. Watches that have a low amplitude are also much more prone to positional errors.
The Risks of High Amplitude
Whereas a low amplitude usually points to problems, an amplitude that is too high can also be a sign of problems with the movement. The most common problems occur when the amplitude of the balance wheel exceeds 310 degrees, a phenomenon that is also known as knocking or rebanking.
Knocking is the result of the balance wheel making a complete 360-degree rotation and hitting the opposite side of the pallet fork. This can lead to the destruction of the roller jewel and other delicate parts inside the movement. High amplitude is normally an outcome of over-lubricating or installing a very strong mainspring when servicing a watch.
For instance, in some cases when a vintage watch is treated with modern lubricants, it can gain a very high amplitude. While the original parts of the watch may have been significantly less efficient, the new lubricant can reduce so much of the friction that the wheel oscillates more than it should, resulting in knocking.
If your timepiece’s amplitude is consistently above 310 degrees, you should get a professional watchmaker to properly look into it. A professional will be able to adjust the lubrication or replace the mainspring so that the movement operates within a healthy amplitude range.
Paragon Calendar Theorema | GM-122-3 | Gold.
Amplitude and Beat per Hour (BPH)
Another metric that is related to the amplitude is beats per hour, which essentially refers to how many times the balance wheel swings back and forth in an hourly direction. Watches with a higher BPH tend to be more accurate and have a smoother movement of the second hand. However, the higher the BPH movement, the more wear it can sustain over time, which may also call for servicing a bit more often.
In contrast, watches with low BPH will be a bit less precise but usually much tougher and lower maintenance. Also, the BPH influences amplitude readings: higher BPH movements show slightly lower amplitudes, whereas their lower BPH counterparts mostly tend to have higher amplitude values.
Final Thoughts
Amplitude is one of the most important indicators that can help you assess your timepiece’s health and performance. If you are particular about maintaining your timepieces or you like to purchase vintage watches, having a timegrapher will make it easier for you to evaluate the condition of your timepieces and know when they require maintenance.
Timepieces with an amplitude that falls in the 270-310 degrees range are ideal, ensuring consistent and accurate timekeeping. If you find that your watch's amplitude falls out of this range, it may be a good time to have it serviced by a professional watchmaker. Properly cared for, with attention and periodic check-ups, your mechanical watch will not only maintain its beauty but also the outstanding timekeeping precision it was designed for.
Paris Theorema | GM-130-5 | Black.
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