Browse Prior Art Database

Magnetic Servo Track Pitch Measurement

IP.com Disclosure Number: IPCOM000013262D
Original Publication Date: 2001-May-29
Included in the Prior Art Database: 2003-Jun-18
Document File: 2 page(s) / 73K

Publishing Venue

IBM

Abstract

Disclosed is the method to measure DC track pitch accuracy with up-to-date track pitch as well as higher pitch to estimate the future possibility. Note that it is required servowriter or equivalent equipment which has the positioning system to make actuator move so that read the signals around the disk as well as write/read function electronics. Write a set of amplitude burst patterns in FIG-1 at designed track pitch (TP1) After writing all tracks across the disk, go back to the initial track and read the signals written before. Assuming that 1st written burst is A, 2nd,3rd for B and C respectively, there are the location where A amplitude average over the sector is the same as one for C. At the location, read A,B,C burst amplitude of all sectors and compute APC1. (FIG-2) Idea here is take above APC1 value average over the multiple revolution so that eliminate non repeatable runout(NRRO) component from the measurement. Move to next track where A amplitude equal to C assuming 2nd,3rd and 4th burst as A, B and C. And measure APC value as APC2. Iterate this way, measure APC value at all tracks. Now APC value itself has no unit. However Track pitch and write/read width relationship described in FIG-3 is expressed as formula (1) By solving formula (1) with known write and read width, APC would translate into meter unit. TP 1 DISK ROTATION

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Magnetic Servo Track Pitch Measurement

Disclosed is the method to measure DC track pitch accuracy with up-to-date track pitch as well as higher pitch to estimate the future possibility. Note that it is required servowriter or equivalent equipment which has the positioning system to make actuator move so that read the signals around the disk as well as write/read function electronics.

Write a set of amplitude burst patterns in FIG-1 at designed track pitch (TP1) After writing all tracks across the disk, go back to the initial track and read the signals written before. Assuming that 1st written burst is A, 2nd,3rd for B and C respectively, there are the location where A amplitude average over the sector is the same as one for C. At the location, read A,B,C burst amplitude of all sectors and compute APC1. (FIG-2) Idea here is take above APC1 value average over the multiple revolution so that eliminate non repeatable runout(NRRO) component from the measurement. Move to next track where A amplitude equal to C assuming 2nd,3rd and 4th burst as A, B and C. And measure APC value as APC2. Iterate this way, measure APC value at all tracks. Now APC value itself has no unit. However Track pitch and write/read width relationship described in FIG-3 is expressed as formula (1) By solving formula (1) with known write and read width, APC would translate into meter unit.

TP 1

DISK ROTATION

Track direction

FIG -1

·····

1

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