Dynamic magnetic information storage or retrieval – Automatic control of a recorder mechanism – Controlling the head
Patent
1986-08-15
1988-10-11
Cardillo, Raymond F.
Dynamic magnetic information storage or retrieval
Automatic control of a recorder mechanism
Controlling the head
360103, 324226, G11B 560, G11B 2102
Patent
active
047775440
ABSTRACT:
A method and apparatus for measuring the flying height of a slider supporting a magnetic transducer in-situ in a direct manner in an operational magnetic disk storage system. The method and apparatus produce relative motion between the magnetic transducer and a magnetic recording medium at a first velocity so that the resulting air bearing positions the magnetic transducer slider at a first flying height from the magnetic medium. A single signal of constant periodicity is written over a predetermined area of the recording medium by the magnetic transducer, and a readback signal is sensed from the predetermined area of the recording medium to produce a first signal. The flying height of the magnetic transducer slider is lowered to substantially zero, and a readback signal is sensed at the lowered flying height to produce a second signal. The first flying height is then calculated as the ratio, expressed in decibels, of the first and second signals times the wavelength divided by a constant. In an alternate embodiment a plurality of signals are recorded and readback signals are simultaneously sensed at two separate wavelengths. In a further embodiment, a signal is recorded which has a spectral content comprising a plurality of different frequencies, and readback signals are simultaneously sensed at two separate wavelengths.
REFERENCES:
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"The Reproduction of Magnetically Recorded Signals", The Bell System Technical Journal, vol. 30, Oct. 1951, pp. 1145-1173, by R. L. Wallace, Jr.
IBM Tech. Discl. Bull. vol. 11, No. 12, May 1969, p. 1650, entitled "Head Flight Height Monitoring", by A. A. Gaudet et al.
"Use of Readback Signal Modulation to Measure Head/Disk Spacing Variations in Magnetic Disk Files", Technical Report No. 11, The Center for Magnetic Recording Research, University of California, San Diego, Dec. 1985, by W-K Shi et al.
"Effect of Flying Height Variation on Offtrack Data Handling", IEEE Trans. on Magnetics, MAG-17-No. 4, Jul., 1981, pp. 1372-1375 by F. Morris et al.
Brown Byron R.
Hu Hung L.
Klaassen Klaas B.
Lum Joseph J.
Van Peppen Jacobus C. L.
Cardillo Raymond F.
Garland Steven R.
International Business Machine Corporation
Schmid, Jr. Otto
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