Method and apparatus for the measurement of defects in magnetic

Details Method and apparatus for the measurement of defects in magnetic Method and apparatus for the measurement of defects in magnetic

1996-10-31

1998-11-17

Psitos, Aristotelis M.

Dynamic magnetic information storage or retrieval

General processing of a digital signal

Head amplifier circuit

360 31, 324212, G11B 5027

Patent

active

058385100

ABSTRACT:
The present invention relates to a method and apparatus for the measurement of defects in magnetic recording disks using a logarithmic amplifier. A magnetic head senses a magnetic field of a magnetic disk and creates a read signal having a varying amplitude. The test apparatus has a squarer which receives and squares the read signal. A logarithmic amplifier coupled to the squarer converts the squared signal to a logarithmic signal. The logarithmic signal is filtered by a first filter. A second filter coupled to the logarithmic amplifier provides an average of the peaks of the logarithmic signal. A digital-to-analog converter coupled to the second filter scales the output of the second filter. The test apparatus further comprises a comparator having a first input and a second input, where the first input is coupled to the first filter, and the second input is coupled to the digital-to-analog converter. The comparator provides an output signal in response to receiving a signal from the first filter having an amplitude that is lower than an average of a predetermined number of peak values of the signal, thereby indicating an error in the disk. In another embodiment, the test apparatus is implemented using a rectifier instead of a squarer.

REFERENCES:
patent: 3609394 (1971-09-01), Lennox
patent: 4881136 (1989-11-01), Shiraishi et al.
patent: 5121057 (1992-06-01), Huber et al.
patent: 5256965 (1993-10-01), Nomura

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