SLIDER-DISK CLEARANCE MEASUREMENTS IN MAGNETIC DISK DRIVES USING THE READBACK TRANSDUCER

A new method is described for noninvasively measuring the mechanical c learance between a recording head slider and the magnetic medium in ha rd-disk drives. The method is based on the detection of the pulse widt h of the read transducer output. A variation in clearance produces a p roportional variation in pulse width. The proportionality factor can b e determined by simulating the spacing loss using a digitized isolated impulse, typical for the respective head-disk combination. Instrument ation is presented that provides an output voltage proportional to the ratio (PW(x)/T) of the pulse width at x% of the peak amplitude PW(x) and the period T of the readback signal. This instrumentation measures the absolute slider-disk clearance by evacuating the air from the dis k drive. The bandwidth is such that clearance dynamics can also be mea sured. This allows clearance measurements as well as the detection of undesirable slider-disk interactions, in situ, in fully operational di sk drives.