Abstract: A disk drive is disclosed comprising a head actuated over a disk, and control circuitry operable to measure a transition response of the disk drive. A test pattern is written to the disk in order to write a plurality of substantially isolated magnetic transitions on the disk. The test pattern is read from the disk to generate a read signal, and the read signal is sampled to generate signal samples. A first plurality of the signal samples is extracted representing a first magnetic transition, and a second plurality of the signal samples is extracted representing a second magnetic transition. A transition response of the disk drive is measured in response to the first and second plurality of signal samples.

Abstract: A disk drive is disclosed comprising a disk comprising a plurality of servo tracks defined by servo sectors, and a head actuated over the disk, wherein the head comprises a read element operable to generate a read signal. The disk drive further comprises a fly height sensor operable to generate a fly height signal for the head, and control circuitry comprising a multiplexer operable to multiplex the read signal and the fly height signal to a transmission line. The multiplexer is configured to select the read signal when reading the servo sectors of a servo track, and configured to select the fly height signal when reading a segment of the servo track between consecutive servo sectors.

Abstract: A method of estimating a writer/reader gap in a disk drive is disclosed. During a first revolution of the disk, a clock is synchronized to a first preamble and used to measure a write delay to write a second sync mark to the disk relative to a first sync mark. During a second revolution of the disk, the clock is again synchronized to the first preamble and used to measure a read delay required to detect the second sync mark relative to the first sync mark. The writer/reader gap is then estimated in response to the measured write delay and the measured read delay, for example, by computing a difference between the measured write delay and the measured read delay.