Using an induction coil sensor to indirectly measure the B-field response in the bandwidth of the transient electromagnetic method

In time-domain systems, the traditional sensor used in transient electromagnetic (EM) systems<br>is an induction coil. This sensor measures a voltage response proportional to the time rate of<br>change of the magnetic field in the EM bandwidth. By simply integrating the digitized output<br>voltage from the induction coil, it is possible to obtain an indirect measurement of the magnetic<br>field in the same bandwidth.<br>The simple integration methodology is validated by showing that there is good agreement<br>between: a) synthetic voltage data integrated to a magnetic field, and b) synthetic magnetic-field<br>data calculated directly. Further experimental work shows that airborne EM magnetic-field data<br>collected with an induction coil correspond quite closely to that measured using a SQUID<br>magnetometer.<br>Comparison of measured voltage and magnetic-field data show that the two sets of profiles have<br>quite different characteristics. The magnetic-field data is better for identifying, discriminating<br>and interpreting good conductors, while suppressing the less conductive targets.