Head DFH protrusion shape calibration by HDI sensor

A method for calibrating a set of dynamic flying height (DFH) controlled read/write heads for use in a multi-head hard disk drive (HDD) comprising:

• providing a hard disk drive (HDD) having at least one rotatable disk therein;
• providing a set of DFH controlled read/write heads, wherein each read/write head in said set has at least a first and second heater element, wherein said first heater element is located adjacent to a write gap and said second heater element is located adjacent to a read gap, wherein each said read/write head is flyable above one of at least said one rotating disk;
• then
• selecting a first read/write head from said set;
• then, while
• supplying power to said at least first and second heaters of said first read/write head at a variable and controllable ratio, producing, thereby, corresponding protrusion profiles;
• measuring a clearance between a point on an ABS of said read/write head closest to said rotating disk for each of said protrusion profiles;
• then
• determining a reference ratio at which a protrusion profile producing a minimum clearance is attained;
• and
• determining a range of ratios about said reference ratio at which measurable minimal acceptable clearances are obtained;
• then
• setting a ratio within said range and operating said first read/write head at that ratio.

A hard disk drive (HDD) including a calibrated a dynamic flying height (DFH) controlled read/write head comprising:

• a HDD having at least one rotatable disk therein;
• a DFH controlled read/write head associated with said at least one rotatable disk, wherein said read/write head has at least a first and second heater element, wherein said first heater element is located adjacent to a write gap and said second heater element is located adjacent to a read gap, wherein said read/write head is flyable above said rotating disk;
• a HDI sensor or its equivalent for measuring clearances and determining touch-downs between said read/write head and said rotating disk;
• a variable and controllable power ratio that is applied to said read/write head, wherein said power ratio produces a corresponding protrusion profile of said write head;
• a range of said variable and controllable power ratios determined for said read/write head within which range said HDI sensor or its equivalent provides signals indicating the onset of touch-downs and, correspondingly, minimal acceptable clearances between said read/write head and said rotating disk;
• a power ratio within said range applied to said read/write head whose value assures a reliable DFH control of said read/write head without the occurrence of touch-down events.