Method and apparatus to detect potential gradients at the earth's surface

摘要

A generator operating at a known frequency produces a pulsed current in the ground, through two electrodes in contact with it, at or near the surface. The line between the electrodes determines a direction. A measurement instrument is connected to the electrodes, detecting a signal in antiphase with the pulses. The signal is filtered, deriving an amplitude whose sign indicates a direction along the electrode line. An Independent claim is included for equipment carrying out the method. Preferred Features: Signal filtering takes place at a frequency between one fifth of the pulsed current frequency and five times this frequency. Filtration passband is a function of the quality of the signal obtained. The measurement instrument working frequency, is a multiple or sub-multiple of the pulsing frequency. The measurement apparatus is synchronized with edges of the pulsed current