Data Acquisition

Acquisition systems are based on lightweight 24-bit 5-channel GPS-synchronized recording units covering the frequency range from 0 to 50 kHz. These can be used in stand-alone mode or from a central control unit. Electrodes are normally low-noise Pb-PbCl2, but for use on frozen ground these may be substituted by special steel-alloy rods. To minimize Johnston noise under conditions of high contact impedance, buffer amplifiers are used at the electrodes, permitting good S/N on ice or on sand dunes.

A variety of magnetic sensors are employed, including the latest generation of low-noise broad-band induction coils which cover the range from 10 KHz to 0.0001 Hz.

Sophisticated processing has been developed to deal with the high level of noise in industrial areas (which include production oil fields and active mines).