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A Correction Technique for Magnetic Disk Fly Heights

IP.com Disclosure Number: IPCOM000102837D
Original Publication Date: 1990-Feb-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 1 page(s) / 49K

Publishing Venue

IBM

Related People

Bowen, AJ: AUTHOR

Abstract

The figure illustrates a method featuring a PZT crystal mounted on a flying glide head used to make improved estimates for actual fly heights of a R/W head. The fly height is the distance between the R/W head and the surface of a rigid magnetic disk surface. This height is calculated by subtracting media roughness measurements from the fly height of the head above a rigid glass disk.

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A Correction Technique for Magnetic Disk Fly Heights

      The figure illustrates a method featuring a PZT crystal mounted
on a flying glide head used to make improved estimates for actual fly
heights of a R/W head.  The fly height is the distance between the
R/W head and the surface of a rigid magnetic disk surface.  This
height is calculated by subtracting media roughness measurements from
the fly height of the head above a rigid glass disk.

      The fly heights on a glass disk are measured for the heads used
in the file and are measured for the glide heads used to certify a
disk 1.  The difference in these two fly heights is called the
"clearance fly height", and it is not dependent on any baseline
information.  This clearance fly height represents the minimum fly
height desired in the file.  The glide head can now be used to
certify the rigid magnetic disk surface profile.

      The glide head detects high frequency (asperities), medium
frequency (waviness), and low frequency (radial curvature) wave
patterns on disk.  Detection is done by mounting a PZT crystal on the
trailing edge of a glide head 2.  The bandwidth of a detection
channel filter 3 is wide enough to pass all the frequencies coming
from the PZT crystal.  The analog signal from the PZT and filter is
processed with a voltage-to-RMS module 4 that converts the filtered
signal to one that is proportional to power being dissipated by the
head/disk interface.  Finally, the output of the RM...