METHOD AND CIRCUITRY FOR IN-SITU MEASUREMENT OF TRANSDUCER/RECORDING MEDIUM CLEARANCE AND TRANSDUCER MAGNETIC INSTABILITY

摘要

A method and circuitry are described for sensing the clearance between a magnetic transducer (10) and a moving magnetic recording medium (9) in a magnetic disk or tape storage system or alternatively sensing the degree of magnetic instability of a magnetic transducer in such a system. Magnetic transitions prewritten on a preselected area of the medium are read to obtain a readback signal. The width of said signal is sensed 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. The voltage is proportional to the width of the readback signal divided by the time period between successive transitions of identical polarity, so as to provide a measurement of clearance or degree of magnetic instability that is independent of the relative velocity between said transducer and medium. The voltage is digitized and compared to a prestored digital reference value. If the clearance is not within a preestablished acceptable range, a desired control operation is initiated, such as stopping movement of the medium. the preselected percentage can vary between 10% and 90%. However, when measuring transducer-medium clearance the percentage is preferably 45%-55%; whereas when measuring degree of instability, the percentage is preferably 30%-35%.