Browse Prior Art Database

Determination of Cause of Erasure in Magnetic Storage Devices

IP.com Disclosure Number: IPCOM000111092D
Original Publication Date: 1994-Feb-01
Included in the Prior Art Database: 2005-Mar-26
Document File: 2 page(s) / 28K

Publishing Venue

IBM

Related People

Brown, BR: AUTHOR [+4]

Abstract

A method is described to determine whether the cause of inadvertent partial erasure of data in a magnetic data storage device is of mechanical or magnetic origin. In many cases, the cause of partial erasure can be determined from a measurement of the symmetry of the readback signal. Erasure caused by a magnetic field having a component parallel/anti-parallel to the magnetization of a recorded track will preferentially modify positive or negative transitions, changing the waveform symmetry. Erasure by mechanical means tends to alter both transitions equally leaving the symmetry unchanged.

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Determination of Cause of Erasure in Magnetic Storage Devices

      A method is described to determine whether the cause of
inadvertent partial erasure of data in a magnetic data storage device
is of mechanical or magnetic origin.  In many cases, the cause of
partial erasure can be determined from a measurement of the symmetry
of the readback signal.  Erasure caused by a magnetic field having a
component parallel/anti-parallel to the magnetization of a recorded
track will preferentially modify positive or negative transitions,
changing the waveform symmetry.  Erasure by mechanical means tends to
alter both transitions equally leaving the symmetry unchanged.

           In a preferred method, the surface is first recorded with
tracks of constant wavelength.  After partial erasure, a spectrum
analyzer or tuned receiver is then used to measure the amplitude of
both the 1st (fundamental) and 2nd harmonic of the readback signal.
The ratio of the 2nd to 1st harmonic is a useful measure of symmetry.
Sensitivity of the measurement can be improved by comparing to the
original symmetry, or to that of a similar unerased track.