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Title: Equipamento eletromagnético para prospecção geofísica e modelamento reduzido
metadata.dc.creator: FONSECA, Nélio Raimundo Medeiros da
metadata.dc.contributor.advisor1: VERMA, Om Prakash
Keywords: Prospecção - Métodos geofísicos
Eletromagnético indutivo
Ataci - BA
Issue Date: 13-Dec-1979
Publisher: Universidade Federal do Pará
Citation: FONSECA, Nélio Raimundo Medeiros da. Equipamento eletromagnético para prospecção geofísica e modelamento reduzido. 1979. 88 f. Dissertação (Mestrado) - Universidade Federal do Pará, Centro de Geociências, Belém, 1979. Curso de Pós-Graduação em Ciências Geofísicas e Geológicas.
Abstract: In the last decade, electromagnetic methods constituted an efficient technique for prospecting of minerals. The objective of this work was to develop an equipment for quantitative electromagnetic prospecting of conducting bodies using dipole-dipole technique. The equipment can also be adopted for reduced scale model experiments. The equipment, in principle, measures the variation in the mutual electromagnetic coupling of two coils, namely the transmitting and the receiving coils. Ground will also contribute to this coupling when the coil system is used near it. This mutual impedance of the transmitter – receiver - ground system shall vary in the vicinity of an anomalous conductor which is manifested as a variation in the signal induced in the search coil. The equipment consists of two sets: a transmitter and a receiver alongwith accessories. The transmitter generates an electromagnetic field at frequencies of 520 Hz and 3090 Hz, and a reference signal for the receiver which is connected through a cable. The receiver first separates the anomalous secondary e.m. field from the uniform primary field. Then this secondary signal is decomposed into two orthogonal components, one inphase and other in quadrature with respect to the primary field. Amplitudes of these phase components can be measured directly in terms of the percentage of the primary field within a precision of 1%, using two amplitude scales. The sensibility of the receiver is 0.5 μV. Electronic circuits were rigorously tested by using precise laboratory instruments. The performance of the e.m. equipment was verified (a) by carrying out classical e.m. model experiments in the laboratory and comparing them with the published results; and (b) by taking some e. m. traverses in an area near Araci, in the State of Bahia, which has been prospected by "Rio Doce Geologia e Mineraçáo S/A-DOCEGEO". All these tests verify a highly good performance of the equipment in terms of its precision and usefulness for field work.
Appears in Collections:Dissertações em Geofísica (Mestrado) - CPGF/IG

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