Magnetic transducer crash anticipation and response method and apparatus
First Claim
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1. A method for denoting the likelihood of an impending crash of a magnetic transducer against a rotating magnetic recording medium due to deterioration in flying height of the transducer below a predetermined acceptable value comprising the steps, while the medium is being rotated at substantially constant velocity, of:
- over a predetermined area of said recording medium, writing one signal at a predetermined amplitude and at a frequency fl ;
reading back said one signal at frequency fl and storing its spectral amplitude;
overwriting said predetermined area with another signal at said predetermined amplitude but at a higher frequency fh ;
then reading back the component of said one signal remaining after said overwriting and storing its spectral amplitude;
calculating the ratio of the spectral amplitudes of said one signal as read before said overwriting and said remaining component of said one signal as read after said overwriting; and
using said ratio to initiate a desired control operation when said ratio denotes that flying height is below said acceptable value.
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Abstract
A self-diagnostic method and apparatus is described for indicating the likelihood of an impending crash of a magnetic transducer or head with a rotating magnetic medium by dynamically and periodically calculating overwrite efficiency for performing a desired control operation when it exceeds a preselected value denoting dangerous proximity of the transducer to the surface of the medium.
48 Citations
18 Claims
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1. A method for denoting the likelihood of an impending crash of a magnetic transducer against a rotating magnetic recording medium due to deterioration in flying height of the transducer below a predetermined acceptable value comprising the steps, while the medium is being rotated at substantially constant velocity, of:
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over a predetermined area of said recording medium, writing one signal at a predetermined amplitude and at a frequency fl ; reading back said one signal at frequency fl and storing its spectral amplitude; overwriting said predetermined area with another signal at said predetermined amplitude but at a higher frequency fh ; then reading back the component of said one signal remaining after said overwriting and storing its spectral amplitude; calculating the ratio of the spectral amplitudes of said one signal as read before said overwriting and said remaining component of said one signal as read after said overwriting; and using said ratio to initiate a desired control operation when said ratio denotes that flying height is below said acceptable value. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. Apparatus for performing a desired control operation responsively to an indication of an impending crash of a magnetic transducer against a rotating magnetic recording medium due to deterioration in flying height of the transducer below a predetermined acceptable value, said apparatus comprising:
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means for writing, over a predetermined area of said recording medium, one signal at a predetermined amplitude and at a frequency fl ; means for reading back said one signal at a frequency fl and storing its spectral amplitude; means for overwriting said predetermined area with another signal at said predetermined amplitude but at a higher frequency fh ; means for reading back the component of said one signal remaining after said overwriting and storing its spectral amplitude; means for calculating the ratio of said spectral amplitudes as read back before and after said overwriting; and means for initiating the desired control operation when said ratio denotes that flying height is below said acceptable value. - View Dependent Claims (9)
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10. Apparatus for performing a desired control operation responsively to an indication of an impending crash of a magnetic transducer against a rotating magnetic recording medium due to deterioration in flying height of the transducer below a predetermined acceptable value, said apparatus comprising:
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means for writing, over a predetermined area of said recording medium, one signal at a predetermined amplitude and at a frequency fl ; means for reading back said one signal at a frequency fl and storing its spectral amplitude; means for overwriting said predetermined area with another signal at said predetermined amplitude but at a higher frequency fh ; means for reading back the component of said one signal remaining after said overwriting and storing its spectral amplitude; means for calculating the ratio of said spectral amplitudes as read back before and after said overwriting; a lookup table containing values of said ratio as measured at different flying heights while the medium is rotated at constant normal velocity; means for comparing the ratio as calculated to a ratio in said table; and means for initiating the desired control operation when said ratio as calculated exceeds a preselected value which denotes that flying height is below said acceptable value.
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11. A method for denoting the likelihood of an impending crash of a magnetic transducer against a rotating magnetic recording medium due to deterioration in flying height of the transducer below a predetermined acceptable value comprising the steps, while the medium is being rotated at substantially constant velocity, of:
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over a predetermined area of said recording medium, writing one signal at a predetermined amplitude and at a frequency fl and then overwriting with another signal at said predetermined amplitude but at a higher frequency fh ; following the overwriting at frequency fh, sensing said one and other signals as read back from said predetermined area to produce first and second readback signals, respectively; calculating the ratio of the amplitudes of said second readback signal to said first readback signal; comparing the ratio as calculated to that in a lookup table; and initiating a desired control operation when said ratio as calculated denotes that the flying height is below said acceptable value. - View Dependent Claims (12, 13, 14, 15, 16)
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17. Apparatus for performing a desired control operation responsively to an indication of an impending crash of a magnetic transducer against a rotating magnetic recording medium due to deterioration in flying height of the transducer below a predetermined acceptable value, said apparatus comprising:
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means operative while the recording medium is rotating at substantially constant velocity for writing, over a predetermined area of said recording medium, one signal at a predetermined amplitude and a frequency fl and then overwriting that signal with another signal at said amplitude but at a higher frequency fh ; means for reading back said one and other signals from said predetermined area after overwriting at frequency fh to produce first and second readback signals, respectively; means for calculating the ratio of the amplitudes of said second readback signal to said first readback signal; a lookup table containing values of said ratio as measured at different flying heights while the medium is rotated at constant normal velocity; means for comparing the ratio as calculated to a ratio in said table; and means for initiating the desired control operation when said ratio as calculated exceeds a predetermined value which denotes that the flying height is below said acceptable value. - View Dependent Claims (18)
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Specification