Cherub Clip-On Digital Guitar Tuner has +/- 1cent tuning precision. While the tuner is clipped onto the headstock, it turns on automatically, and turns off automatically while it is removed away from the headstock. If the tuner is kept on the guitar headstock, it will power off automatically in 5 minutes no matter it is in use or not. Built-in piezo sensor for better tuning. When it is in tune, the backlit turns green. When it is sharp, the backlit turns red. When it is flat, the Backlit turns orange. Tuning result: Guitar: 6E 5A 4D 3G 2B 1E. Tuning range: A0 (27.5Hz) equivalent to C8 (4186Hz). It has clip detection method and auto tuning mode. Power supply is 3V (CR2032) lithium battery.