Method and circuitry for in-situ measurement of transducer/recording medium clearance and transducer magnetic instability

A method for sensing magnetic instability of a magnetic transducer with respect to a moving magnetic recording medium in a magnetic storage system, comprising the steps of:

• writing magnetic transitions on a preselected area of the medium;
• reading the transitions from said area in order to obtain a readback signal;
• sensing the width of said readback signal at a predetermined amplitude level which is a preselected percentage of its base-to-peak amplitude to provide a voltage corresponding to the width of said signal at said level;
• and
• using said voltage to measure the degree of instability of said transducer.

A magnetic storage system, comprising:

• a movable magnetic recording medium;
• a magnetic transducer for reading, during movement of the medium, magnetic transitions prewritten on a preselected area of the medium in order to obtain a readback signal;
• means for sensing the width of said readback signal at a predetermined amplitude level which is a preselected percentage of its base-to-peak amplitude to provide a voltage corresponding to the width of said signal at said level;
• and
• means responsive to said voltage to denote the clearance between said transducer and the moving medium.

A magnetic storage device having a data channel, comprising:

• a movable magnetic storage medium;
• magnetic transducer means for writing a signal comprising magnetic transitions in a data band on the medium at a frequency less than that at which the amplitude of the channel has rolled off to 75% of its low frequency amplitude;
• means for reading back the signal from the recorded transitions;
• means for generating a voltage proportional to the width of said readback signal at a preselected amplitude level that is between 10% and 90% of its peak-to-base amplitude;
• means for comparing said voltage to a predetermined previously stored reference value generated for said preselected amplitude level and providing an output when said voltage varies from a prescribed acceptable range;
• and
• means responsive to said output to initiate a desired control operation.

A disk file comprising, in combination:

• a rotatable magnetic recording disk;
• a magnetic transducer supported to fly with clearance above the disk during rotation of the latter, while reading magnetic transitions from a track on the disk to generate an analog readback signal;
• means for sensing the width of said readback signal at a predetermined amplitude level which is a preselected percentage of its base-to-peak amplitude to provide a voltage corresponding to the width of said signal;
• means for converting said voltage to a digitized value;
• and
• means for comparing said digitized value to a predetermined digital reference value to determine whether the clearance lies within a preestablished acceptable range.

A magnetic storage device comprising, in combination:

• a rotatable magnetic recording disk;
• a magnetic transducer for reading magnetic transitions from a track on the disk to generate an analog readback signal;
• means for sensing the width of said readback signal at a predetermined amplitude level which is a preselected percentage of its base-to-peak amplitude to provide a voltage corresponding to the width of said signal at said level;
• means for converting said voltage to a digitized value;
• and
• means for comparing said digitized value to a predetermined digital reference value to measure the degree of instability of the transducer.