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Detection of Magnetic Disk Asperities by Differential Pressure Sensing on a Slider Air-Bearing Surface

IP.com Disclosure Number: IPCOM000038009D
Original Publication Date: 1989-Sep-01
Included in the Prior Art Database: 2005-Jan-31
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Smith, GJ: AUTHOR

Abstract

Asperities on magnetic recording disks which pass beneath the air-bearing rails of a slider create pressure perturbations. This is due to a changing spacing condition for the air-bearing. The magnitude of a pressure perturbation depends primarily on the asperity size and shape, slider flying height, and the disk velocity. If the magnitude of the perturbation is large enough, an asperity can be detected by using pressure transducers on the air-bearing rails. This method of asperity detection does not require head-to-disk asperity contact.

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Detection of Magnetic Disk Asperities by Differential Pressure Sensing on a Slider Air-Bearing Surface

Asperities on magnetic recording disks which pass beneath the air-bearing rails of a slider create pressure perturbations. This is due to a changing spacing condition for the air-bearing. The magnitude of a pressure perturbation depends primarily on the asperity size and shape, slider flying height, and the disk velocity. If the magnitude of the perturbation is large enough, an asperity can be detected by using pressure transducers on the air-bearing rails. This method of asperity detection does not require head-to-disk asperity contact.

Fig. 1 shows a two-element linear transducer array placed near the trailing edge on one of the rails. The sensing surface of each transducer is made flush with the air-bearing rail surface. The linear arrangement, with the axis of the array parallel to the longitudinal rail axis, provides low sensitivity to pressure changes resulting from slider pitching, rolling, and vertical translation.

In Fig. 2, the output of each sensor (1 and 2) is connected to an amplifier and programmable-threshold exclusive OR circuit. The exclusive OR functions as a phase detector, whereby only sensor outputs which are out of phase will produce a logic true output. The proximity of the two transducers insures that the outputs will remain nearly in phase for slider pitch, roll, and translation. Only for a pressure perturbation due to a disk defect will...