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Hanna, Saba A.

Electrical and Computer Engineering

2009

PhD

Naturally occurring electromagnetic oscillating fields in the very low frequency (VLF) range of the spectrum, from 1 kHz to 200 kHz are weak and difficult to detect under normal conditions. These naturally occurring VLF electromagnetic events are observed during thunderstorms, in certain mountain winds, and during earthquakes. On the other hand, man-made VLF electromagnetic fields are stronger, and have caused interference with electronic equipment and possibly pose a public health risk. Typical sources of these VLF emissions include television sets, video display terminals (VDT), electric motors, fluorescent lights, certain medical devices, radio stations, induction heating, and the ground wave emergency network (GWEN) used for military communications. Our main goals for writing this thesis are.
A. First, describe the development of a triaxial "VLF Gaussmeter", which can be made portable. This "VLF Gaussmeter" is based on a microcontroller with a built-in 10- bit A/D converter and has been designed to measure the magnetic flux density and frequency across the wide VLF bandwidth (BW). A digitized resolution of 0.2 mG is used for the 0 mG to 200 mG range, and 2 mG resolution for the range of 2 mG to 2000 mG. The meter has been designed to include the following features: automatic or manual range selection, data logging, single axis mode, peak hold, RS-232 communication port, and analog recorder output.
B. Second, describe how the meter is used for taking measurements of the frequencies and the magnetic field levels in residential and occupational environments, particularly around cathode ray tube displays, hybrid cars, and induction heating units. C. Third, compare the measurements to the established or recommended limits according to national standards so that engineers and scientists can understand these nontrivial electrical measurements.