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Plotting Technique for Magnetic Disk Read Signal Amplitude

IP.com Disclosure Number: IPCOM000090353D
Original Publication Date: 1969-Apr-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 32K

Publishing Venue

IBM

Related People

Rook, CR: AUTHOR

Abstract

The amplitude topography of the readback signal from a disk recording surface is recorded photographically. The read head output voltage is fed through a rectifier and low-pass filter 1, to obtain the read signal amplitude envelope. Voltage level discriminator 2 produces a pulse when the filter 1 output signal is equal to a reference voltage received from source 3. The output pulses from discriminator 2 are summed with the reference voltage in summing amplifier 4 to make the pulse amplitude a function of the reference voltage. The pulses from amplifier 4 are applied to oscilloscope 5 to modulate the intensity of the scanning beam. Signal levels from amplifier 4 are such that the beam is blanked except when a pulse is present.

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Plotting Technique for Magnetic Disk Read Signal Amplitude

The amplitude topography of the readback signal from a disk recording surface is recorded photographically. The read head output voltage is fed through a rectifier and low-pass filter 1, to obtain the read signal amplitude envelope. Voltage level discriminator 2 produces a pulse when the filter 1 output signal is equal to a reference voltage received from source 3. The output pulses from discriminator 2 are summed with the reference voltage in summing amplifier 4 to make the pulse amplitude a function of the reference voltage. The pulses from amplifier 4 are applied to oscilloscope 5 to modulate the intensity of the scanning beam. Signal levels from amplifier 4 are such that the beam is blanked except when a pulse is present.

The oscilloscope 5 scan is in the form of a circular trace, under the control of generator 6. The scan is synchronous with the disk rotation and the radius is proportional to the track location. In operation, several sweeps are made on each track of the disk using different reference levels. The read head is then moved to another track and the sequence is repeated.

The trace on the oscilloscope is photographed by camera 7 by time exposure. On the photograph the intensified spots appear as a series of continuous lines representing the equal amplitude profiles with intensity increasing with amplitude. In this manner, a permanent record of the disk amplitude topography indicating variat...