Fly height extraction system

• US 8,699,169 B2
• Filed: 03/02/2013
• Issued: 04/15/2014
• Est. Priority Date: 01/09/2004
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Biskeborn, Robert Glenn
• Primary Examiner(s): Negron, Daniell L
• Application Number:
  US13/783,244
• Publication Number:
  US 20130222942A1
• Time in Patent Office: 409 Days
• Field of Search: None
• US Class Current: 360/67
• 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 system for monitoring fly height between a magnetic recording medium and a transducing head, comprising:

a signal analyzer and a data processor;

said signal analyzer generating signal amplitude values of frequency components within multi-frequency signals sensed on the recording medium;

said data processor using said signal amplitude values to calculate a magnetic spacing change value relative to the recording medium and the transducing head; and

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

2. A system in accordance with claim 1 wherein said multi-frequency signals comprise media noise sensed on the recording medium.

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

4. A system in accordance with claim 2 wherein said signal analyzer decomposes said media noise into said frequency components using a Fast Fourier Transform conversion process.

5. A system in accordance with claim 2 wherein said signal analyzer decomposes said media noise into said frequency components using a spectrum analyzing process.

6. A system in accordance with claim 2 wherein said data processor calculates said magnetic spacing change value using at least two of said signal amplitude values for at least two of said frequency components of said media noise.

7. A system in accordance with claim 1 wherein said data processor determines transducing head wear using a measurement of transducing head signal amplitude after accounting for changes in amplitude due to conditions other than head wear.

8. A system in accordance with claim 1 wherein the transducing head comprises a magnetoresistive (MR) read sensor and said data processor determines transducing head wear using a measurement of change in MR stripe height of the read sensor while using a measurement of resistance of a write coil component of the transducing head to correct for temperature drift.

9. A system in accordance with claim 8 wherein said data processor calculates a change in fly height as the difference between said magnetic spacing change value and said change in MR stripe height.

10. A system in accordance with claim 1 wherein the system is embodied in one of a data storage system or a test apparatus for characterizing recording heads or recording media.

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

a signal analyzer and a data processor;

said signal analyzer generating signal amplitude values of frequency components within media noise sensed on the recording medium; and

said data processor calculating a magnetic spacing change value from said signal amplitude values, and adjusting said magnetic spacing change value as necessary to reflect transducing head wear.

12. A system in accordance with claim 11 wherein said media noise corresponds to a substantially random pattern of magnetic domains formed on the recording medium using one of an A.C. erasure technique, a D.C. erasure technique or a bulk erasure technique.

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

14. A system in accordance with claim 11 wherein said signal analyzer decomposes said media noise into said frequency components using a Fast Fourier Transform conversion process.

15. A system in accordance with claim 11 wherein said signal analyzer decomposes said media noise into said frequency components using a spectrum analyzing process.

16. A system in accordance with claim 11 wherein said data processor calculates said magnetic spacing change value using at least two of said signal amplitude values for at least two of said frequency components of said media noise.

17. A system in accordance with claim 11 wherein said data processor determines transducing head wear using a measurement of transducing head signal amplitude after accounting for changes in amplitude due to conditions other than head wear.

18. A system in accordance with claim 11 wherein the transducing head comprises a magnetoresistive (MR) read sensor and said data processor determines transducing head wear using a measurement of change in MR stripe height of the read sensor while using a measurement of resistance of a write coil component of the transducing head to correct for temperature drift.

19. A system in accordance with claim 18 wherein said data processor calculates a change in fly height as the difference between said magnetic spacing change value and said change in MR stripe height.