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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.

Other References

• "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