A number of electromagnetic instruments with fixed frequency transmitterreceiver has been developed by Centre de Recherches Geophysiques (Garchy, France) in order to measure magnetic susceptibility and electrical resistivity of ground. A dipole-dipole induction tool (SH3) was built for some meter penetration from the surface (spacing=1.5m, frequency=8kHz) and has allowed electrical resistivity and magnetic susceptibility mapping to be applied to archaeological exploration. A "ROMULUS" probe (spacing 0.85m, frequency=4kHz) has followed as a borehole version (diameter 0.04m) for mineral exploration by Bureau de Recherches Geologiques et Minieres (Orleans, France). Another borehole instrument called "ERIC" was then designed on the same principle (frequency=1kHz) but with variable transmitter-receiver spacing (5m, 10 m, 20m) for ten meter scale investigation of conductive bodies around the hole. The method, its field of application and design of equipments is described. Several examples of shallow investigation surface maps and borehole induction logs are presented.

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