Case history: magnetic interference from a power supply to a computer terminal-magnetic shielding was the solution!

This paper discusses interference to a video display terminal which was rack-mounted in the near vicinity of a high current switch mode AC power supply. Preliminary testing showed that the interference (visualized as `waves´ on the screen) was due to low frequency magnetic interference emanating from the (non-shielded) power supply. The installation of magnetic shielding over the power supply eliminated the problem. Results are presented of measurements of the magnetic fields at the VDT location both prior to and after the application of magnetic shielding and recommendations for future designs are detailed