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Head Flying Height Assessment

IP.com Disclosure Number: IPCOM000084377D
Original Publication Date: 1975-Nov-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 2 page(s) / 36K

Publishing Venue

IBM

Related People

Bate, G: AUTHOR [+2]

Abstract

The flying height between a magnetic medium and a recording head is assessed by analyzing the shape of the electrical signals detected by the recording head, when reading information that it has recorded.

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Head Flying Height Assessment

The flying height between a magnetic medium and a recording head is assessed by analyzing the shape of the electrical signals detected by the recording head, when reading information that it has recorded.

A recording head initially writes information on a magnetic medium. The medium is then rewound, and the recording head's write winding is sensed, instead of being driven, during a second recording pass (or a separate read head can be used). A trace of the resulting signal (Fig. 1) will be asymmetrical about a line through its peak, if the head was in contact with the medium during the write pass. The amount of symmetry is accurately determined by plotting the ratio of the integrated left (V(L)) and right (V(R)) amplitudes greater than 67% of the peak (Fig. 2).

When the head is not in contact with the medium, the amplitude trace will be symmetric, and the ratio plot gives a unique curve characteristic of the head-to- medium relationship. A "standard" ratio curve may be used as a comparative test for checking the uniformity of later manufactured heads, media and transport adjustment. The ratio may also be calibrated to become an absolute indication of the flying heights of individual heads.

The necessary calculating may be continuously performed by the circuit in Fig. 3. Positive signals derived from the differentiated head signals are passed by operational amplifier Q1 to be further differentiated by amplifier Q2. Amplifiers Q3 and Q...