Browse Prior Art Database

Dynamic Fly Height Monitor

IP.com Disclosure Number: IPCOM000060584D
Original Publication Date: 1986-Apr-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 2 page(s) / 54K

Publishing Venue

IBM

Related People

Maurine, RJ: AUTHOR [+3]

Abstract

The Dynamic Fly Height Monitor is a device for measuring the instantaneous changes in separation of a read/write head from a rotating disk surface. A specially adapted capacitance probe slider 5 is used as shown in Fig. 1. The capacitance probe is a standard slider with 5-mil wires 9 drilled vertically into each corner and lapped flush with the flying surface of the head. The probe will measure the capacitance variations between the wires' ends and the disk substrate surface 7, thus indicating the fly height variations, WS. The circuit for measuring the capacitance variation consists of an RC-type multivibrator oscillator serving as input to a phase-locked loop (PLL) shown in Fig. 2. The PLL consists of a phase detector (Exclusive OR) 11, filter 12 and voltage-controlled oscillator (VCO) 14.

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Dynamic Fly Height Monitor

The Dynamic Fly Height Monitor is a device for measuring the instantaneous changes in separation of a read/write head from a rotating disk surface. A specially adapted capacitance probe slider 5 is used as shown in Fig. 1. The capacitance probe is a standard slider with 5-mil wires 9 drilled vertically into each corner and lapped flush with the flying surface of the head. The probe will measure the capacitance variations between the wires' ends and the disk substrate surface 7, thus indicating the fly height variations, WS. The circuit for measuring the capacitance variation consists of an RC-type multivibrator oscillator serving as input to a phase-locked loop (PLL) shown in Fig. 2. The PLL consists of a phase detector (Exclusive OR) 11, filter 12 and voltage-controlled oscillator (VCO) 14. The capacitance variation frequency modulates the input oscillator 15, causing the VCO 14 to track the frequency variation. The VCO input voltage (error voltage) is amplified to produce a Wo = K1 WS. The equations are:

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