Simultaneous measurement of contact potential and slider body clearance in a magnetic disk drive

• US 7,310,197 B2
• Filed: 06/15/2005
• Issued: 12/18/2007
• Est. Priority Date: 06/15/2005
• Status: Expired due to Fees

• Current Assignee: Western Digital Technologies Incorporated (Western Digital Corporation)
• Original Assignee: Hitachi Global Storage Technologies Netherlands BV (Western Digital Corporation)
• Inventors: Knigge, Bernhard E., Baumgart, Peter Michael, Duwensee, Malk
• Primary Examiner(s): Korzuch; William R.
• Assistant Examiner(s): OLSON, JASON C
• Application Number:
  US11/152,912
• Publication Number:
  US 20060284620A1
• Time in Patent Office: 916 Days
• Field of Search: None
• US Class Current: 360/75
• CPC Class Codes: G11B 5/6017 using capacitive measurement

Abstract

A method for simultaneously measuring contact potential and slider body clearance in a hard disk drive. In embodiments of the present invention, a plurality of direct current (DC) pulses are applied between a slider body and a hard disk of a magnetic disk drive. The contact potential voltage between the slider body and the hard disk is determined in response to applying the plurality of direct current (DC) pulses. The voltage of the plurality of direct current (DC) pulses is increased until a contact between the slider body and the hard disk is detected.

Claims

1. A method for simultaneously measuring contact potential and slider body clearance in a hard disk drive, said method comprising:

applying a plurality of direct current (DC) pulses between said slider body and a hard disk of a magnetic disk drive, wherein said plurality of direct current (DC) pulses are applied at a plurality of discrete locations on said hard disk, wherein each pulse of said plurality of direct current (DC) pulses comprise an equivalent voltage and duration;

ceasing said applying a plurality of direct current (DC) pulses,

measuring a contact potential voltage between said slider body and said hard disk at each of said plurality of discrete locations in response to applying said plurality of direct current (DC) pulses at said each of said plurality of discrete locations on said hard disk; and

increasing the voltage of said plurality of direct current (DC) pulses at each of said plurality of discrete locations until a contact between said slider body and said hard disk at each of said plurality of discrete locations is detected, increasing said equivalent voltage and duration for each pulse; and

measuring clearance of said slider body relative to said hard disk, said clearance measured at said contact potential voltage and said voltages for causing said contact.

2. The method as recited in claim 1 wherein said applying a plurality of direct current (DC) pulses further comprises:

applying a plurality of positive direct current (DC) pulses between said slider body and said hard disk at each of said plurality of discrete locations, wherein each of said positive direct current (DC) pulses comprise an analogous voltage and duration;

ceasing said applying a plurality of positive direct current (DC) pulses; and

applying a plurality of negative direct current (DC) pulses between said slider body and said hard disk at each of said plurality of discrete locations, wherein each of said negative direct current (DC) pulses comprise an equal voltage and said duration.

3. The method as recited in claim 1 further comprising:

deriving an average clearance change of said slider body corresponding to said contact potential voltage and said voltages for causing said contact.

4. The method as recited in claim 3 wherein said deriving an average clearance change further comprises:

determining that said average clearance change comprises maximum clearance of said slider body.

5. The method as recited in claim 4 further comprising:

measuring said average clearance change of said slider body using an optical range determining device.

6. The method as recited in claim 4 further comprising:

determining said average clearance change of said slider body by sensing a variation in amplitude of a readback signal at each of said plurality of discrete locations.

7. The method as recited in claim 1 further comprising:

detecting a change in the current flow between said slider body and said hard disk when said contact occurs.

8. A system for simultaneously measuring contact potential and clearance between a slider body clearance and a hard disk of a hard disk drive comprising:

a housing;

a disk pack mounted to said housing and comprising said hard disk that is rotatable relative to said housing, the disk pack defining an axis of rotation and a radial direction relative to the axis;

a slider body mounted to said housing and disposed proximate to said hard disk;

a voltage adjuster coupled with said slider body and with said hard disk, said voltage adjuster comprising;

a direct current (DC) pulse generator for generating a plurality of direct current (DC) pulses at a plurality of discrete locations on said hard disk, wherein each pulse of said plurality of direct current (DC) pulses comprise an equivalent voltage and duration; and

a direct current (DC) voltage controller;

a processor coupled with said voltage adjuster; and

a detector coupled with said slider body and with said processor, said detector for measuring said contact potential, said detector for measuring said clearance.

9. The system of claim 8 wherein said voltage adjuster generates another plurality of direct current (DC) pulses at said plurality of discrete locations, said another plurality of direct current (DC) pulses having a bias different than said plurality of direct current (DC) pulses, and wherein each pulse in said another plurality of direct current (DC) pulses comprise an equal voltage and said duration.

10. The system of claim 9 wherein said processor determines an average clearance change of said slider body in response to said plurality of direct current (DC) pulses and said another plurality of direct current pulses.

11. The system of claim 8 wherein said detector comprises an optical range determining device.

12. The system of claim 8 wherein said detector comprises a component for sensing a variation in amplitude of a readback signal at each of said plurality of discrete locations, wherein each of said plurality of discrete locations is a designated portion of a data track of said hard disk.

13. The system of claim 8 further comprising:

a contact detector for detecting a contact between said slider body and said hard disk at each of said plurality discrete locations in response to an increase in a voltage generated by said direct current (DC) voltage adjuster.

14. The system of claim 8 wherein said voltage adjuster generates said plurality of direct current (DC) pulses having a positive bias and said another plurality of direct current (DC) pulses having a negative bias.

15. A system comprising:

a disk pack comprising at least one hard disk;

a slider body disposed proximate to said hard disk;

a voltage adjusting means for generating a plurality of direct current (DC) pulses between said hard disk and said slider body at a plurality of discrete locations of said hard disk, wherein each of said plurality of direct current (DC) pulses comprise an equivalent voltage and duration; and

a controlling means for determining a contact potential voltage between said slider body and said hard disk and for controlling said voltage adjuster wherein the voltage of said plurality of direct current (DC) pulses is increased until a contact between said slider body and said hard disk is detected.

16. The system of claim 15 wherein said voltage adjusting means further comprises:

a pulse generating means for generating a direct current (DC) pulse having a positive voltage bias and for generating a direct current (DC) pulse having a negative voltage bias, wherein said positive voltage bias pulse and said negative voltage bias pulse comprise an analogous duration; and

a voltage controlling means for controlling the voltage of said plurality of direct current (DC) pulses.

17. The system of claim 15 further comprising:

a detecting means for detecting a contact between said slider body and said hard disk.

18. The system of claim 15 further comprising:

a measuring means for measuring clearance change of said slider body relative to said hard disk.

19. The system of claim 18 wherein said controlling means is further for determining an average clearance change of said slider body in response to said plurality of direct current (DC) pulses.

20. The system of claim 15 wherein said controlling means is for causing said voltage adjusting means to generate each of said plurality of direct current (DC) pulses when said slider body is proximate to each of said plurality of discrete locations of said hard disk and wherein said each of said plurality of discrete locations is a portion of a data track.