For the Spring Drive, the mainspring is wound and the unwinding power of the mainspring moves the hands in the same manner as the mechanical watch.
It differs from the mechanical watch only in the speed-regulating unit (mechanism for controlling accuracy).
Accuracy of mechanical watches depends on a balance spring attached to a part called the balance. This part has properties for expanding and contracting with temperature changes, and influences the accuracy of a watch. Accuracy of the Spring Drive is never largely influenced by temperature changes like that of mechanical watches since the crystal oscillator controls it.
Accuracy of the Spring Drive
Average monthly rate of ±15 seconds (equivalent to daily rate of ±1 second)* is the accuracy of a watch when it is worn on a wrist at a temperature range between 5°C and 35°C.
For Cal. 9R96, 9R16 and 9R15, the average monthly rate is ±10 seconds (equivalent to daily rate of ±0.5 second).
Difference in position
For mechanical watches, the accuracy is influenced even by a difference in position or direction of a watch. This is also caused by the balance that controls the accuracy of mechanical watches. Due to the difference in position, the area where the shaft of the balance contacts with other parts differs, and such differences in resistance influence the accuracy. As the Spring Drive adopts a crystal oscillator not a balance, the accuracy is not influenced by a difference in position.
Mechanical watches are susceptible to impacts. If a mechanical watch was subject to impact, amplitude of vibration of the balance (angle for which the balance rotates right and left) is changed, and even the form of the balance spring is changed. In this regard, the Spring Drive is superior to mechanical watches in impact resistance because it adopts a crystal oscillator not a balance.
Parts that become worn or severely damaged are the balance, pallet fork, and escape wheel & pinion which are collectively called the speed-regulating unit or escapement. These parts “come into contact or collide” mutually and control unwinding of the mainspring.
For the Spring Drive, wear and damage occur less than mechanical watches since the spinning speed of the glide wheel is adjusted by a “contact-free” electromagnetic brake. However, as the structure of gear train is the same as mechanical watches, abrasion powder may be generated by contact of the wheels & pinions. An overhaul is recommend every three to four years.