Amplitude is the measure of the amount of rotation in the swing of the balance wheel, in either direction, usually expressed in degrees. In a running watch, the balance wheel swings or rotates clockwise and counterclockwise. Each swing in either direction is called a “beat”. Amplitude is the number of degrees of rotation of the beat. Amplitude is higher, typically in the range of about 270 to 315 degrees, when a watch is lying flat or in the “dial up” or “dial down” position. Amplitude usually falls when the watch is in a vertical position, primarily due to increased friction. Amplitude can also fall as the watch winds down and the mainspring delivers less power. Amplitude that is too high or too low, or that changes too much in different positions, can indicate a problem with the movement.
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