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Browse Prior Art Database

Read/Write Offset Measurement by Head Switching

IP.com Disclosure Number: IPCOM000112551D
Original Publication Date: 1994-May-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Ozawa, Y: AUTHOR

Abstract

Disclosed is a measurement for read/write offset of magnetoresistive head by switching plural heads supported by an actuator in a hard disk drive.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 100% of the total text.

Read/Write Offset Measurement by Head Switching

      Disclosed is a measurement for read/write offset of
magnetoresistive head by switching plural heads supported by an
actuator in a hard disk drive.

      The plural heads include a basic head with a known read/write
offset.  At first, the basic head is selected and the actuator is
controlled to cause the basic head to follow a predetermined track.
Then, the head selection is switched from the basic head to one of
remaining heads to be measured, and an offtrack of the measured head
is read.  The offtrack value of the measured head and the known
read/write offset of the basic head sum up to an offset between read
and write elements of the measured head.

      The Figure shows a relation between Head 0 (basic head) and
Head 1 (measured head) when Head 0 is following Track N.  After
switching from Head 0 to Head 1, an offtrack (A) of Head 1 is
measured by obtaining a position error signal of track servo.  Then,
a read/write offset (C) of Head 1 is determined as sum of the
offtrack (A) of Head 1 and the known offset (B) of Head 0.

     C = A + B

      Since it takes a short time to measure the read/write offset
for each head, this technique is very useful for a large hard disk
drive which has many heads.