Measurements of ELF and VLF Emissions from VDTs.

人们对“Vdts的电磁辐射”给予了关注。VDT是一种视频显示终端--计算机监视器屏幕。根据IEEE EMC标准1140 1994，测量了极低频(5赫兹-2千赫)和甚低频(2千赫-400千赫)的电磁辐射。测量了4个CRT(14‘)的电磁辐射，结果表明，ELF的磁场强度为73.4nT~656.0nT，VFL的磁场强度为73.4nT~1693.9nT，场强为2.5V/m。阐明了极低频的垂直偏转绕组和甚低频的水平偏转绕组、反激式变压器是产生磁场的来源。

Attention has been given to "electromagnetic emissions from VDTs". A VDT is a video display terminal-a computer monitor screen. I measured the electromagnetic emissions in ELF (5Hz-2kHz) and VLF (2kHz-400kHz) based on IEEE EMC standard 1140 1994. As a result of measuring the electromagnetic emissions from 4 CRTs (14'), the magnetic field strength was 73.4nT-656.0nT in ELF,and 73.4nT-1693.9nT,electric field strength was 2.5v/m in VLF.To seek for the source of magnetic field, the distribution aroud the VDT were measured in detail. It was clarified that the source of the magnetic field was vertical deflection winding in ELF and horizontal deflection winding, flyback transformer in VLF.