Video display terminal fringing magnetic field measurements

Abstract

Possible occupational health or public health risks due to video display terminals (VDTs) are addressed. The authors note the errors of current jargon and correctly define the terms needed to describe the fringing magnetic flux density near any magnetically deflected, raster scan, cathode ray tube display. Theory and preliminary measurements have shown that the ELF AC electric field related to VDT display electronics is small, and the electromagnetic field strength at any frequency is truly negligible as an occupational health risk near any cathode ray tube display. Application of Maxwell's equations shows that the commonly used pickup coil responds to the derivative of magnetic flux density. The transducer needs an integrator to respond properly to the sawtooth waveforms of deflection fields. Correct measurements of VDT fringing magnetic fields are presented. A Swedish test method is briefly discussed. The conclusion from this work is strong. Theory and these measurements show there is not a verifiable occupational health risk from the fringing ELF electric or magnetic fields or any frequency electromagnetic fields near VDTs. >