Patent ID: 7916599
Filing Date: 2011-03-29
Classification: G11B

Abstract:
1. A method to balance spindles in a plurality of disk drives, the method comprising: a) rotating the spindle of one of the plurality of disk drives; b) while the spindle of that one of the plurality of disk drives is rotating, measuring an initial amplitude and an initial phase of an electrical signal that corresponds to an initial imbalance for that one of the plurality of disk drives; c) determining the initial imbalance based on the initial amplitude and an amplitude calibration; d) selecting one of a plurality of balancing masses, the selection being based on the initial imbalance; e) attaching the selected balancing mass to the spindle of that one of the plurality of disk drives, with the selected balancing mass at an angular position selected based upon the initial phase and a phase calibration; f) again rotating the spindle of that one of the plurality of disk drives; g) while the spindle of that one of the plurality of disk drives is again rotating, measuring a final amplitude and a final phase of an electrical signal that corresponds to a final imbalance for that one of the plurality of disk drives; h) determining the final imbalance based on the final amplitude and an amplitude calibration; i) repeating steps a through h for each of the plurality of disk drives, recording the final imbalance and the initial imbalance for each of the plurality of disk drives; j) adjusting the amplitude calibration based on a comparison of a measured distribution and a theoretical distribution of the final imbalance versus the initial imbalance.