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Spectrum measurements of electromagnetic-noise in coal mines.

Authors
Bensema-WD; Adams-JW
Source
Proceedings of Thru-the-Earth Electromagnetics Workshop, August 15-17, 1973, Colorado School of Mines, Golden, Colorado. Geyer RG, ed., Pittsburgh, PA: U.S. Department of the Interior, Bureau of Mines, Grant G0133023, 1973 Dec; :151-155
Link
NIOSHTIC No.
20033486
Abstract
A portable, multichannel battery-operated mine-permissible measurement system was developed to measure the rms magnetic-field noise spectrum in the frequency range from 100 Hz to 375 kHz. During each measurement, the entire spectrum is measured simultaneously through the use of time-domain recordings which are later analyzed by Fast Fourier Transform processing. Dynamic ranges of 60 dB in a 125 Hz bandwidth are obtained for spectra covering the range from 100 Hz to 100 kHz. The method also allows a three-dimensional display of the way spectrum occupancy changes with time. Calibration and correction procedures allow absolute field strength measurement with an uncertainty of not more than 3 dB. We feel that further analysis of the system errors will allow this uncertainty to be reduced to less than 1 dB. Ambient magnetic field noise spectra covering frequencies from 100 Hz to 100 kHz are given for several underground coal mine locations. Examples are also given of magnetic field noise on the surface above the mine, noise in the mine face area, noise radiated by specific equipment, the voltage spectrum found on a 600 V dc trolley wire, and noise picked up simultaneously on loops and on roof support bolts.
Keywords
Mining-industry; Mining-equipment; Underground-mining; Radio-waves; Electromagnetic-energy; Electromagnetic-fields; Electromagnetic-wave-transmission; Electromagnetic-interference
Publication Date
19731231
Document Type
Conference/Symposia Proceedings
Editors
Geyer-RG
Fiscal Year
1974
NTIS Accession No.
NTIS Price
Source Name
Proceedings of Thru-the-Earth Electromagnetics Workshop, August 15-17, 1973, Colorado School of Mines, Golden, Colorado
State
CO; DC
Performing Organization
National Bureau of Standards
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