Caliber 9RB2
9R SPRING DRIVE MOVEMENT
Spring Drive U.F.A.
Caliber 9RB2
The pursuit of high accuracy has always been the cornerstone of Grand Seiko’s values. Receiving the new U.F.A. designation, which stands for “Ultra Fine Accuracy,” Caliber 9RB2 boasts a level of precision defined not by accuracy in seconds per day, week, or month, but by accuracy over one year. The movement has an astounding annual rate of ±20 seconds, or approximately ±3 seconds per month, setting a new standard among wristwatch movements powered by a mainspring*.
*As of April 2025, based on Grand Seiko’s research.
Spring Drive utilizes the properties of a crystal that vibrates at a constant frequency to measure the passage of time. When external factors such as temperature changes, humidity, and gravity are applied to the crystal oscillator, the frequency changes, resulting in tiny errors. Over time, they may cause the accuracy to deviate slightly.
The±20-seconds-per-year accuracy of Caliber 9RB2 is achieved by thoroughly reconsidering the manufacturing and processing methods for the in-house, three-month-aged quartz oscillator and a newly designed temperature-compensating IC. Furthermore, by incorporating a newly developed regulator switch, accuracy deviation due to aging after assembly is minimized more than ever before.
SPECIFICATIONS
- One-piece Center Bridge
- Power-reserve indicator
- Date display
What makes 9R Spring Drive special?
Spring Drive, one of the great innovations in modern watch making history, regulates a spring-driven movement with state-of-the-art electronic technology that functions without batteries or other external power source. Its sole power source is a mainspring, which drives a series of gears. A rotor, connected to the end of these gears, generates a small electrical charge that activates an electronic circuit and quartz oscillator. Its accuracy is unprecedented for a watch wound by a mainspring. The development of the 9R Spring Drive movement was possible only because Grand Seiko is one of the few manufacturers with expertise in both mechanical and electronic watches.
