A Complicate Response of Compact EMI Sensors over Shallow Local Conductive Targets

The paper presents a modeling of different type of compact EMI sensors response over a local conductive shallow depth targets. The target as well as Tx and Rx coils are approximated by the vertical magnetic dipoles. All the calculations are made under the model of uniform conductive space. Three types of coil configuration are considered. First is semi two coil device with fixed transmitter that carries out the sounding by the changing both the intercoil separation and frequency. The second type is three coil multi frequency sensor with fixed geometry. All the coils in previous configuration are arranged at the same plane. The last new type is multi frequency sensor with the receiver coils that placed at the line inclined to the horizon. A field example is considered as well. The theoretical and practical investigations show that shallow local conductive anomalies produce sophisticated response for compact EMI sensors with spaced coils. It yields from one to four anomalies over one target. The new proposed coil configuration produces the single anomaly