Desenvolvimento De Um Sistema Hlem De Campo Magnético Induzido, No Domínio Da Freqüência, Para Prospecção Mineral

An electromagnetic system was developed<br>using some parts of an old Slingram ABEM EM35/88<br>as transmitter and receiver coils and matching<br>transformers. Modern circuits with low noise lock-in<br>amplifiers and analog multiplier were used to detect<br>signal from a high magnetic permeability receiver<br>coil. In phase and quadrature voltage of lock-in<br>amplifiers outputs were achieved using square<br>waveform reference from the transmitter coil circuit.<br>Comparison of these voltage by a precise analog<br>multiplier give us the electrical apparent conductive<br>of the overburden layer (conductor). One third lock-in<br>circuit was used to adjust the spacing intercoil by<br>nulling the total field component.