Tech Tip 06 Magnetic Fields Can Distort Computer Screens -
Distortion of characters on computer screen - Magnetic fields
(EMF) affecting screen - Electric fan near screen - Screen is
near power transformer or other "heavy" electrical distribution
- Relocate monitor away from EMF source - Relocate EMF source -
Shield monitor from fields - Change monitor refresh rate An
individual reported a computer monitor screen was "jumping
around". An investigation revealed that an Electromagnetic Field
(EMF) of 11 mG was interfering with the screen. The distortion
appeared as a wavy screen and oscillating of text primarily
around the edges of the screen. A similar screen is illustrated
in figure 1. Measurements in the area suggested that the EMF was
due to electrical distribution circuits running under the floor.
Magnetic field interference to monitor screens does not usually
occur until a level of roughly 10 mG. Some high resolution
screens have detected image distortion at 3-4 mG. Magnetic field
strength decreases rapid