Fly height extraction system

• US 8,531,796 B2
• Filed: 01/09/2004
• Issued: 09/10/2013
• Est. Priority Date: 01/09/2004
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Biskeborn, Robert Glenn
• Primary Examiner(s): Negron, Daniell L
• Application Number:
  US10/754,392
• Publication Number:
  US 20050152055A1
• Time in Patent Office: 3,532 Days
• Field of Search: None
• US Class Current: 360/75
• CPC Class Codes: G11B 21/12 Raising and lowering; Back-spacing or forward-spacing along track; Returning to starting position otherwise than during transducing operation
• CPC Class Codes: G11B 2220/90 Tape-like record carriers
• CPC Class Codes: G11B 27/36 Monitoring, i.e. supervising the progress of recording or reproducing for digital recording G11B20/00 and s.gr.; for monitoring, testing or measuring of TV recorders of the type covered by H04N5/76 and subgroups, see H04N17/06
• CPC Class Codes: G11B 5/00813 magnetic tapes
• CPC Class Codes: G11B 5/455 Arrangements for functional testing of heads; Measuring arrangements for heads
• CPC Class Codes: G11B 5/6005 Specially adapted for spacing from a rotating disc using a fluid cushion

Abstract

A system and method for monitoring fly height between a magnetic recording medium and a transducing head. In a first exemplary embodiment, magnetic spacing change value is calculated using media noise on the recording medium (instead of prerecorded tones) to provide a broadband frequency distribution that results in improved Wallace equation accuracy. In a second exemplary embodiment, a magnetic spacing change value is acquired by any suitable method but is adjusted as necessary to reflect transducing head wear, thus providing a methodology for calculating changes in fly height by taking into account the signal loss that is attributable to wear. In this way, a basic understanding of the mechanism causing changes in magnetic spacing is achieved.

Claims

1. A method for monitoring fly height between a magnetic recording medium and a transducing head, comprising:

calculating a magnetic spacing change value relative to the recording medium and the transducing head; and

adjusting the magnetic spacing change value as necessary to reflect transducing head wear.

2. A method in accordance with claim 1 wherein said magnetic spacing change value is calculated from media noise sensed on the recording medium.

3. A method in accordance with claim 2 wherein said media noise is processed so as to be substantially free of electronic power spectra noise generated by read channel circuitry associated with the transducing head.

4. A method in accordance with claim 2 wherein said magnetic spacing change value is calculated after decomposing said media noise into frequency components using a Fast Fourier Transform conversion process.

5. A method in accordance with claim 2 wherein said magnetic spacing change value is calculated after decomposing said media noise into frequency components using a spectrum analyzing process.

6. A method in accordance with claim 2 wherein said magnetic spacing change value is calculated using at least two frequency components of said media noise.

7. A method in accordance with claim 1 wherein transducing head wear is determined by measuring transducing head signal amplitude after accounting for changes in amplitude due to conditions other than transducing head wear.

8. A method in accordance with claim 1 wherein the transducing head comprises a magnetoresistive (MR) read sensor and transducing head wear is determined by measuring a change in MR stripe height of the read sensor while using measured resistance of a write coil component of the transducing head to correct for temperature drift.

9. A method in accordance with claim 8 wherein a change in fly height is calculated as the difference between the magnetic spacing change value and the change in MR stripe height.

10. A method in accordance with claim 1 wherein the magnetic recording medium comprises magnetic tape and the transducing head is a tape head.

11. A method for monitoring fly height between a magnetic recording medium and a transducing head, comprising:

sensing media noise on the recording medium;

calculating a magnetic spacing change value from the media noise; and

adjusting said magnetic spacing change value as necessary to reflect transducing head wear.

12. A method in accordance with claim 11 wherein said media noise is generated by forming a substantially random pattern of magnetic domains on the recording medium using one of an A.C. erasure technique, a D.C. erasure technique or a bulk erasure technique.

13. A method in accordance with claim 11 wherein said media noise is processed so as to be substantially free of electronic power spectra noise generated by read channel circuitry associated with the transducing head.

14. A method in accordance with claim 11 wherein said magnetic spacing change value is calculated after decomposing said media noise into frequency components using a Fast Fourier Transform conversion process.

15. A method in accordance with claim 11 wherein said magnetic spacing change value is calculated after decomposing said media noise into frequency components using a spectrum analyzing process.

16. A method in accordance with claim 11 wherein said magnetic spacing change value is calculated using at least two frequency components of said media noise.

17. A method in accordance with claim 11 wherein transducing head wear is determined by measuring transducing head signal amplitude after accounting for changes in amplitude due to conditions other than head wear.

18. A method in accordance with claim 11 wherein the transducing head comprises a magnetoresistive (MR) read sensor and transducing head wear is determined by measuring a change in MR stripe height of the read sensor while using measured resistance of a write coil component of the transducing head to correct for temperature drift.

19. A method in accordance with claim 18 wherein a change in fly height is calculated as the difference between the magnetic spacing change value and the change in MR stripe height.