Browse Prior Art Database

Three-Axis Magnetic Field Detector

IP.com Disclosure Number: IPCOM000099606D
Original Publication Date: 1990-Feb-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 3 page(s) / 76K

Publishing Venue

IBM

Related People

Dickerson, JA: AUTHOR [+4]

Abstract

Image distortion as observed on the screen of a CRT monitor can be eliminated at the time of manufacture. External magnetic fields present in the environment where the monitor ultimately operates degrades this "near perfect" image. In Fig. 1, a magnetic field detector is shown attached to the rear cover of a monitor. The operator manually operates the mechanical actuator at the time of initial monitor installation. Three magnetic field components (X-Y-Z) will be measured with a knob rotation of 270o .

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Three-Axis Magnetic Field Detector

       Image distortion as observed on the screen of a CRT
monitor can be eliminated at the time of manufacture.  External
magnetic fields present in the environment where the monitor
ultimately operates degrades this "near perfect" image.  In Fig. 1, a
magnetic field detector is shown attached to the rear cover of a
monitor.  The operator manually operates the mechanical actuator at
the time of initial monitor installation.  Three magnetic field
components (X-Y-Z) will be measured with a knob rotation of 270o .

      Conditions occasionally exist where fields from nearby AC power
cables or a desk-type fluorescent lamp will cause modulated image
distortion.  For these situations, the actuator knob can be left in
the position which provides dynamic compensation to cancel the
"problem" field.

      Calibration is the "home" position for the actuator knob (see
Fig.  2).  The first magnetic component "Z" is measured after the
knob has been rotated 180o .  When this position is reached, the knob
extends 6 mm toward the operator (making the "Y" measurement).  With
an additional rotation of 90o, the final measurement is made (X).

      A Hall effect magnetic field detector and support
analog/digital electronics is contained on the printed circuit card
located on the hinge opposite the knob.

      Infrared light sources and photo detectors are used to
determine magnetic sensor position.