Abstract: A well logging system using an induction measurement. The system includes an emitting coil and a plurality of receiving coils. The emitting coil induces eddy currents in the medium surrounding the coils. The receiving coils then measure magnetic fields produced by the eddy currents. Two of the receiving coils are selected at a time and used as a receiving coil and a counter-receiving coil. The signal generated in the two coils are used to determine a weighted difference to better define the vertical resolution of the device. Compensation coils may be added to remove fields which are induced in the receiving coils directly from the transmitting coil.

Abstract: A microdevice is provided for measuring the electromagnetic characteristics of a medium in a borehole. The microdevice includes at least one emitting or transmitting coil (31), and at least one receiving coil (41,51). The microdevice generates an A.C. voltage at the terminals of the transmitting coil and measures a signal at the terminals of the receiving coil. The microdevice also includes an E-shaped electrically insulating, soft magnetic material circuit serving as a support for each of the coils and which is positioned adjacent to the medium in the borehole.