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Avalanche Curve Calibration Method for Single Disk Tester

IP.com Disclosure Number: IPCOM000099586D
Original Publication Date: 1990-Feb-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 2 page(s) / 51K

Publishing Venue

IBM

Related People

Aoyagi, A: AUTHOR [+3]

Abstract

Disclosed is a method for calibrating missing pulse detectability of a single disk tester for disk surface defect testing. This calibration method is able to realize a more accurate setting of a clip level for missing pulse detection to maintain the same detectability against test head change, drift of electric circuits for read signal processing and tester noise condition change.

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Avalanche Curve Calibration Method for Single Disk Tester

       Disclosed is a method for calibrating missing pulse
detectability of a single disk tester for disk surface defect
testing.  This calibration method is able to realize a more accurate
setting of a clip level for missing pulse detection to maintain the
same detectability against test head change, drift of electric
circuits for read signal processing and tester noise condition
change.

      Generally, the relationship between the number of missing
pulse- type defects on hard disk surfaces and a clip level for
missing pulse detection is similar to the well-known V/I
characteristic curve of diode.  The figure shows the relationship
called the "Avalanche Curve".

      The procedure for the avalanche curve calibration method for a
single disk tester is described as follows:
)  Make a standard disk for the defect test calibration by
characterizing the avalanche curve of the disk varying clip level for
missing pulse detection.  (The tester condition, including test
heads, when the standard disk is made becomes a standard of tester
condition for subsequent tests.)  The avalanche curve obtained here
is called the standard curve.
2)  Prior to testing, run a defect test with the standard disk and
characterize its avalanche curve.
3)  Compare the curve with the standard curve and obtain an offset in
a clip level, as shown in the figure.
4)  Adjust the clip level in order to compensate the offset.
5) ...