GEOLOGICAL SURVEY MEASURING DEVICE Russian patent published in 1997 - IPC

FIELD: measurement of electrical resistivity variations with time. SUBSTANCE: device has ac generator connected to point sources in the form of electrodes, communication line, recorder, receiving elements. Device is also provided with control unit, two synchronous detectors, band filter, comparison unit, phase shifter, two variable-gain matching amplifiers. Receiving elements are, essentially, two electric-field strength transducers; control unit inputs are connected to one of point sources and to ac generator and its outputs, to control inputs of synchronous detectors whose outputs are connected to recorder and second inputs, to comparison unit output via band filter; inverting input of comparison unit is connected to communication line through first variable-gain matching amplifier. Noninverting input of comparison unit is also connected through series-connected phase shifter and second variable-gain matching amplifier to communication line linked with outputs of first and second electric-field strength transducers. Each transducer has series-connected primary sensor, transformer, and preamplifier; transducers are arranged symmetrically to one of point sources. In addition, control unit has input current transformer and comparator, multiplier, frequency divider, all connected in series with it; outputs of comparator and frequency divider function as outputs of control unit. EFFECT: improved measurement accuracy. 2 cl, 3 dwg