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Testing Magnetic Tape With A Magnetometer

IP.com Disclosure Number: IPCOM000095430D
Original Publication Date: 1964-Jan-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 36K

Publishing Venue

IBM

Related People

Speliotis, DE: AUTHOR [+2]

Abstract

The method is for testing the magnetic properties of a complete reel of magnetic tape without unwinding or destroying any part of the tape. The mode of operation is based on the principles of the vibrating sample or vibrating coil magnetometer. Properties determined include coercivity, remanence coercivity, saturation magnetization, saturation remanence, and the field required to produce any fraction of saturation remanence. Complete hysteresis loops are also obtained in an almost static fashion. Variations in the composition or thickness of the ferromagnetic tape surface can also be estimated.

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Testing Magnetic Tape With A Magnetometer

The method is for testing the magnetic properties of a complete reel of magnetic tape without unwinding or destroying any part of the tape. The mode of operation is based on the principles of the vibrating sample or vibrating coil magnetometer. Properties determined include coercivity, remanence coercivity, saturation magnetization, saturation remanence, and the field required to produce any fraction of saturation remanence. Complete hysteresis loops are also obtained in an almost static fashion. Variations in the composition or thickness of the ferromagnetic tape surface can also be estimated.

In the upper right drawing, a synchronous motor, electromechanical transducer, is coupled to rigid rod 10 on the lower end of which is reel holder 11 driven with oscillations of small amplitude and low frequency. A 1/16 inch displacement at 25 cps is quite adequate. The magnetic field between the two poles of electromagnet 12 induces a moment in the ferromagnetic sample which has a vertical spatial variation due to the oscillations. By changing the electromagnetic field, the induced moment can also be varied with time. These variations are picked up by paired coil assembly 13 and recorded or viewed on an oscilloscope. Reel holder 11 is a light nonmagnetic case with a clamped removable side to facilitate insertion and removal of a reel.

The lower drawing shows that coil assembly 13 has pairs of radially and concentrically arranged pickup coils. These are mounted on either side of holder 11 and at equivalent positions along the same horizontal line. Since it is desirable to get a good average m...