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Flux Sensing System with a High Flux Density Timing

IP.com Disclosure Number: IPCOM000092528D
Original Publication Date: 1966-Dec-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Bradford, RC: AUTHOR [+3]

Abstract

Timing pulses are generated by mu-metal disk 10. This is provided with discrete areas 12 of embedded mu-metal. The areas are sensed by transducer 14. If the disk 10 is made entirely of mu-metal, areas 12 can be etched through. The change from mu-metal to no mu-metal is sensed by transducer 14. The latter is not used in a conventional manner by sensing flux emanating from a source such as a magnetic media, but is used to sense segments of high-permeability media within the vicinity of the air gap of the head.

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Flux Sensing System with a High Flux Density Timing

Timing pulses are generated by mu-metal disk 10. This is provided with discrete areas 12 of embedded mu-metal. The areas are sensed by transducer
14. If the disk 10 is made entirely of mu-metal, areas 12 can be etched through. The change from mu-metal to no mu-metal is sensed by transducer 14. The latter is not used in a conventional manner by sensing flux emanating from a source such as a magnetic media, but is used to sense segments of high- permeability media within the vicinity of the air gap of the head.

An excitation current having a frequency f is applied to single-turn coil 16. Depending upon the magnitude of the current, the core material near the holes through which coil 16 is wound gives rise to a circular magnetic flux surrounding each hole. The material near the hole thus becomes more or less saturated twice during each cycle. The reluctance of the entire transducer 14 varies accordingly.

This results in a single output rich in the second harmonic 2f of frequency f.

Because of the unavoidable unbalance of the magnetic reluctance about the holes and because of the magnetic nonlinearities, substantial amounts of the fundamental and higher harmonics are present. Highly selective band filter amplifier 26 is required to extract the useful information in the form of the signal- modulated second harmonic from the total head output as generated from coil
16.

In this system the flux within head 14 is produce...