Prospecting modulo and the device null which utilize the commercial cycle signal

摘要

PURPOSE:To simply execute measurement with high accuracy by deriving an underground specific resistance from a ratio of an electric field component and a magnetic field component of the sum of a primary electromagnetic field radiated from a transmission line and a secondary electromagnetic field generated by a current induced under the ground by the primary electromagnetic field. CONSTITUTION:Two pieces of potential electrodes 121, 122 are embedded under the ground at a prescribed internal, usually at an interval of about 20-30m, and also, an earth electrode 13 is embedded. Subsequently, an induction coil 11 is placed so as to be orthogonal to a transmission line. A measuring instrument body 101 amplifies detecting signals from the induction coil 11 and an electric field sensor 12 by amplifiers 21, 22, respectively, and also, 50Hz or 60Hz and its higher harmonic component are extracted by filters 31, 32 and applied to a data processor 4. The data processor 4 brings an obtained signal to high speed Fourier transform and detects intensity of an electric field and a magnetic field to each frequency, and from a ratio of the electric field and the magnetic field, an underground specific resistance is calculated, and outputted by an output device 5 consisting of a printer, etc.