Browse Prior Art Database

Offset Compensation for MR Head

IP.com Disclosure Number: IPCOM000104580D
Original Publication Date: 1993-May-01
Included in the Prior Art Database: 2005-Mar-19
Document File: 2 page(s) / 42K

Publishing Venue

IBM

Related People

Kisaka, M: AUTHOR

Abstract

This article describes how to compensate offset between a read element and a write element of a MR head for a hard disk drive. An MR head has two elements for read and write respectively. Therefore, it is required to measure offset value. By writing special pattern at unused tracks, the value is measured.

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Offset Compensation for MR Head

      This article describes how to compensate offset between a read
element and a write element of a MR head for a hard disk drive.  An
MR head has two elements for read and write respectively.  Therefore,
it is required to measure offset value.  By writing special pattern
at unused tracks, the value is measured.

      Fig. 1 shows typical servo pattern written on a disk.  Track
center is determined at the position where output from A (1) is equal
to that from B (2).  In case of a MR head, there is a write element
(3).  Therefore, if data is written at the position where read
element output from A and B are equal, to read the data, it is
required to shift a read element so that a read element can be on the
center of the written data.  Three methods to find the offset are
described.

      Method 1 - Fig. 2 shows principal.  While following at the
center position determined by a read element, burst data (4) is
written by a write element.  Then a read element is shifted till
amplitude of the written burst data becomes maximum.  By saving the
position where the amplitude becomes maximum, offset value between a
read element and a write element can be obtained.

      Method 2 - Instead of searching maximum amplitude, error rate
of the written data is measured.  The position where error rate
becomes best is stored as offset.

      Method 3 - Fig. 3 shows the pattern.  While following at the
half track positions d...