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UBC Theses and Dissertations

The fluxgate electric field meter : a feasibility study Cover, Keith Sean


The fluxgate electric field meter is a new solid-state instrument capable of measuring slowly varying electric fields equally well in an insulating or conducting medium with high resolution. The field meter determines the strength of an electric field by measuring the potential difference between two insulated electrodes immersed in the electric field. The electrode insulation is important because it eliminates the contact potential noise between the conductive material of the electrode and a conductive medium. The capacitance of the insulated electrodes is of the order of 10pF; therefore measurement of the potential difference between the electrodes requires an electrometer with extremely low bias current and high input resistance. A novel electrometer was concieved and designed to accomplish this task. The new electrometer is a solid-state analogue of the vibrating-capacitor electrometer and is claimed to have zero bias current. MOS capacitors are substituted for the vibrating capacitor. The noise level for the crude, proof-of-concept electrometer was 220μVHz[sup -1/2] at 1Hz. This noise level is only 20 dB worse than the best commerical device I could locate. A crude, proof-of-concept electric field meter constructed with the electrometer had a high frequency cutoff of 150Hz and low frequency cutoff of 100μHz. Possible applications of the fluxgate electric field meter include measurement of atmospheric and interplanetary electric fields, measurement of static charge buildup, and geophysical surveys.

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