Talking about the error of mechanical watches, what is the international allowable error range of mechanical watches?

- May 20, 2019-

Why do mechanical watches often have errors? Time is measured by the continuation of exactly the same repetitive process. When measuring time, people compare time with a known periodic repetitive process. Mechanical watches use the mechanical oscillator composed of the pendulum yarn as the time base. The accuracy of the watch will mainly depend on the stability of the oscillation period of the pendulum yarn.




What is the allowable error range of the mechanical meter?




The daily error of ordinary quartz watches is less than 0.5 seconds, which is one tenth of that of mechanical watches. This is mainly due to the high and stable oscillation frequency of quartz oscillator in quartz watches. The principle of high frequency running time is found in the process of long-term research on how to improve the accuracy of clock running time. The higher the frequency of oscillator, the more stable the oscillation and the stronger the anti-interference ability, the more accurate the watch will be. The oscillation frequency of quartz electronic meter is 32768Hz, which is 10,000 times higher than that of ordinary fast pendulum mechanical meter. Therefore, quartz electronic meter is more accurate than mechanical watch. In addition, due to the structure of the watch body, due to the gravitational force of the earth, the offset of the horizontal and vertical positions will produce potential difference. The clocks are tightened to relax, and the torque is unbalanced. In addition, affected by the external temperature, magnetic field, vibration and so on, the mechanical watch can not achieve the accuracy of quartz electronic watch even if it increases some frequencies.




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However, the oscillation stability of the pendulum yarn is affected by the following factors:




(1) The effect of swing




The elasticity of the spring will directly affect the amplitude of the pendulum wheel, so it also affects the timeliness of the watch. The so-called "isochronism" refers to a phenomenon that the amplitude of the oscillating object will not affect the vibration period, but the pendulum and yarn system in the watch is not free oscillation. Its frequent impact and collision with the parts of the escapement system is a combined vibration state of "forced + free", so it is bound to be affected by the escapement system. The momentum of impulse transmission determines the swing and the time of their relationship. Of course, the shorter the time, the better.




(2) The influence of position change




The main change of position is the change of plane and vertical plane. There are only three elevations in the plane (surface up and surface down). They are: table down, table left, table up). Table right will not occur when normal wearing, so there are five positions in total. Firstly, the change of position causes the change of the friction surface of the tenon of the pendulum wheel, and the increase of the friction surface. Secondly, the imbalance of the pendulum wheel is more obvious and prominent under the action of gravity. Additional moment acts on the swing wheel, and the gravity of the yarn acts on the yarn. All of these make the yarn system of the watches'pendulum wheel be affected by different magnitudes at each position.




(3) The influence of fast and slow clip of hairspring




Most watches have hairpin clips. The purpose of the fast and slow clips is to adjust the travel time accuracy conveniently. However, because there is a gap between the fast and slow clips and hairpin, also known as "swing gap", its existence greatly destroys the timeliness of watches and increases the position error of watches.




(4) The influence of temperature change




The change of temperature will change the geometrical size of the pendulum wheel and the yarn. Every minor change of these key components will directly affect the oscillation period, and the temperature will also change the viscosity of the surface oil, so that the moment transmission and the oscillation of the watch gear train will change.




(5) The influence of magnetic field




Many parts of watches are made of steel, so they are easy to be magnetized, including nickel-based hairspring, which is weak magnetic. When the watches are magnetized by external magnetic field or parts have been magnetized, the swing cycle of the swing wheel will be greatly disturbed by magnetic force, usually the watches go very fast.




(6) The impact of shock and vibration




Vigorous impact vibration also has an impact on the cycle of the pendulum wheel vibration, especially on watches with low swing or low frequency. As for watches with low swing amplitude or low frequency, severe impact vibration has damaged the tenon or hairspring of the pendulum wheel, which will inevitably bring travel time failure to the watches.




(7) Machining Tolerance of Watch Core Parts




Watch is the most precise and minimal mechanical device. The tolerance range can be as small as 1/1000mm. The processing error of parts is also one of the important reasons for watches travel time error.




(8) Other factors




The main reason is that the watch case is not tightly sealed, so the change of humidity, moisture and air pressure will affect the accuracy of the watch travel time, but also easy to have small dust and foreign objects into the watch, affecting the work of the watch parts. There is also a problem called "no needle" which belongs to the fault of the table.




Watches have the best accuracy when they are in full-string state. To make their watches travel accurately, they must be as full as possible. This is more important for automatic watches. Because the tightening of the spring of the automatic watch is directly related to the time you wear it and the movement you wear, the premise is to ensure that you have enough exercise.




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Watches have different travel time accuracy in different positions




This is what we call the position error of watches. Better watches should be tested at three temperatures and five directions when they leave the factory. Five positions are: top (dial up), bottom (3 o'clock down), left (12 o'clock down), top (9 o'clock down) and right (6 o'clock down), which are not commonly used (unless you bring the watch to the palm or right hand). According to statistics, most people spend about 35% of their time on the surface of their watches in one day, 30% on the left, 25% on the bottom and 10% on the other. Therefore, they use watches to travel in different positions.