Disk drive qualifying head/disk interface using jitter seek excitation

1. A disk drive comprising:

a disk comprising a plurality of tracks;

a head coupled to an actuator arm actuated over the disk; and

control circuitry operable to:

first seek the head a first seek distance from a first track to a second track;

read data from the second track for a first time interval to generate a first read signal;

second seek the head a second seek distance from the second track to a third track, wherein the second seek distance is less than the first seek distance;

read data from the third track for a second time interval to generate a second read signal;

third seek the head a third seek distance from the third track to a fourth track, wherein the third seek distance is less than the second seek distance;

read data from the fourth track for a third time interval to generate a third read signal; and

evaluate the first, second, and third read signals to qualify the disk drive,

wherein the first, second, and third seeks are executed in proximity so as to excite the actuator arm with a jitter motion.

2. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to write the data before reading the data.

3. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to evaluate the first, second, and third read signals by measuring an error rate of the read signals.

4. The disk drive as recited in claim 1 , wherein the first, second, and third time intervals determine the jitter motion.

5. The disk drive as recited in claim 1 , wherein the jitter motion comprises a decaying oscillation.

6. A disk drive comprising:

a disk comprising a plurality of tracks;

a head coupled to an actuator arm actuated over the disk; and

control circuitry operable to:

first seek the head a first seek distance from a first track to a second track;

maintain the head over the second track for a first time interval;

read data from the second track during at least part of the first time interval to generate a first read signal;

second seek the head a second seek distance from the second track to a third track;

maintain the head over the third track for a second time interval;

read data from the third track for at least part of the second time interval to generate a second read signal;

third seek the head a third seek distance from the third track to a fourth track;

maintain the head over the fourth track for a third time interval;

read data from the fourth track for at least part of the third time interval to generate a third read signal; and

evaluate the first, second, and third read signals to qualify the disk drive,

wherein the first, second, and third seeks and the first, second, and third intervals cause the actuator arm to oscillate at an oscillation frequency.

7. The disk drive as recited in claim 6 , wherein the control circuitry is further operable to write the data before reading the data.

8. The disk drive as recited in claim 6 , wherein the control circuitry is further operable to evaluate the first, second, and third read signals by measuring an error rate of the read signals.

9. The disk drive as recited in claim 6 , wherein the control circuitry is further operable to adjust at least one of the first, second, and third intervals in order to adjust the oscillation frequency.

10. The disk drive as recited in claim 6 , wherein the first, second, and third seek distances are substantially equal.

11. The disk drive as recited in claim 6 , wherein:

the second seek distance is less than the first seek distance; and

the third seek distance is less than the second seek distance.

12. The disk drive as recited in claim 6 , wherein the control circuitry is further operable to adjust at least one of the first, second, and third seek distances in order to adjust the oscillation frequency.

13. A method of operating a disk drive, the disk drive comprising, a disk comprising a plurality of tracks, and a head coupled to an actuator arm actuated over the disk, the method comprising:

first seeking the head a first seek distance from a first track to a second track;

reading data from the second track for a first time interval to generate a first read signal;

second seeking the head a second seek distance from the second track to a third track, wherein the second seek distance is less than the first seek distance;

reading data from the third track for a second time interval to generate a second read signal;

third seeking the head a third seek distance from the third track to a fourth track, wherein the third seek distance is less than the second seek distance;

reading data from the fourth track for a third time interval to generate a third read signal; and

evaluating the first, second, and third read signals to qualify the disk drive, wherein the first, second, and third seeks are executed in proximity so as to excite the actuator arm with a jitter motion.

14. The method as recited in claim 13 , further comprising writing the data before reading the data.

15. The method as recited in claim 13 , further comprising evaluating the first, second, and third read signals by measuring an error rate of the read signals.

16. The method as recited in claim 13 , wherein the first, second, and third time intervals determine the jitter motion.

17. The method as recited in claim 13 , wherein the jitter motion comprises a decaying oscillation.

18. A method of operating a disk drive, the disk drive comprising, a disk comprising a plurality of tracks, and a head coupled to an actuator arm actuated over the disk, the method comprising:

first seeking the head a first seek distance from a first track to a second track;

maintaining the head over the second track for a first time interval;

reading data from the second track during at least part of the first time interval to generate a first read signal;

second seeking the head a second seek distance from the second track to a third track;

maintaining the head over the third track for a second time interval;

reading data from the third track for at least part of the second time interval to generate a second read signal;

third seeking the head a third seek distance from the third track to a fourth track;

maintaining the head over the fourth track for a third time interval;

reading data from the fourth track for at least part of the third time interval to generate a third read signal; and

evaluating the first, second, and third read signals to qualify the disk drive, wherein the first, second, and third seeks and the first, second, and third intervals cause the actuator arm to oscillate at an oscillation frequency.

19. The method as recited in claim 18 , further comprising writing the data before reading the data.

20. The method as recited in claim 18 , further comprising evaluating the first, second, and third read signals by measuring an error rate of the read signals.

21. The method as recited in claim 18 , further comprising adjusting at least one of the first, second, and third intervals in order to adjust the oscillation frequency.

22. The method as recited in claim 18 , wherein the first, second, and third seek distances are substantially equal.

23. The method as recited in claim 18 , wherein:

the second seek distance is less than the first seek distance; and

the third seek distance is less than the second seek distance.

24. The method as recited in claim 18 , further comprising adjusting at least one of the first, second, and third seek distances in order to adjust the oscillation frequency.