Browse Prior Art Database

Flyheight Modulation Measurement

IP.com Disclosure Number: IPCOM000115875D
Original Publication Date: 1995-Jul-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 71K

Publishing Venue

IBM

Related People

Kerwin, GJ: AUTHOR

Abstract

A method for measuring the curvature of a disk in a hard disk file insitu is disclosed. Also disclosed is the insitu method of measuring the incidents of mechanical contact between the recording head and an asperity in the media. Both of these measurements are achieved by using the samples of a sampling detection data channel to ascertain flyheight modulation.

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Flyheight Modulation Measurement

      A method for measuring the curvature of a disk in a hard disk
file insitu is disclosed.  Also disclosed is the insitu method of
measuring the incidents of mechanical contact between the recording
head and an asperity in the media.  Both of these measurements are
achieved by using the samples of a sampling detection data channel to
ascertain flyheight modulation.

      Disclosed is a means of determining the peak variation in
flyheight of a recording head in its normal operating environment.
The base flyheight detection scheme, previously described in a patent
application, accurately measures changes in flyheight by measuring
the deviations of the value of the zero samples exiting a sampling
detector from the ideal zero sample values.  The sample deviations
are equated to changes in resolution resulting from varying
separation loss in the read back waveform.  Described is a way to use
this measurement technique to rapidly quantify changes in flyheight
that result from either media imperfections known as "disk flatness"
and "mechanical defects".  The scheme involves fast repetitive use of
the data sample flyheight measurement to detect rapidly changing
flyheight and so detect the sources of these flyheight modulations.
The algorithm averages a variety of sample sizes and collects these
samples at varying intervals depending on the expected source of the
flyheight modulation.  For example, the algorithm for assessing disk
f...