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# Shielded Degauss Apparatus

IP.com Disclosure Number: IPCOM000115429D
Original Publication Date: 1995-May-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 4 page(s) / 81K

IBM

## Related People

Beeteson, J: AUTHOR [+1]

## Abstract

Although there is no medical evidence showing a detrimental effect on health caused by magnetic fields, there are various organizations that have promoted standards for a reduction in magnetic emissions from equipment such as computer monitors.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 79% of the total text.

Shielded Degauss Apparatus

Although there is no medical evidence showing a detrimental
effect on health caused by magnetic fields, there are various
organizations that have promoted standards for a reduction in
magnetic emissions from equipment such as computer monitors.

In the manufacture of monitors, it is normal to degauss the CRT
screen with a handheld coil which produces a substantial magnetic
field at mains frequency.

In Fig. 1, the field lines can be clearly seen to be symmetric
above and below the solenoid.  In this instance the apparatus is used
in
free air (&mu. = 1).

Shown in Fig. 1 is a simulation of the magnetic field from a
conventional manual degauss coil.  This operates to produce a strong
alternating magnetic field which is symmetrical about the front and
rear of the apparatus.  In operation, this is placed near the monitor
to be degaussed and then moved away from the monitor gradually,
resulting in the field intensity falling to a near-zero value.  The
actual determination of the magnetic field strength at an arbitrary
point from it's source is mathematically complex but for all
practical
purposes with regard to the present invention can be considered as an
inverse square law.  The field strength is defined as:
H = I over <4 pi> integral from C
<dl times r sub 0> over r sup 2 %%%% (A%m sup -2)%%%,%%%%
B = mu sub 0 mu sub r H

Note the r sup 2 term.

The placing of a structure, such as th...