Geomagnetic Electrokinetrograph (GEK): A Technological Advancement in Long-Term Continuous Monitoring of Fluid Flow Velocity

Based on research performed at the Woods Hole Oceanographic Institution, a compact Geomagnetic Electrokinetograph has been developed capable of measuring underwater electric fields in the fraction of a millivolt range. While principally designed for the measurement of large-scale fluid flow, its applications include small-scale fluid flow, corrosion generated fields and detection of natural and man-made telluric fields. This instrument utilizes silver-silver chloride (AgAgCl) electrodes which interface with the fluid medium through hollow water or gel filled tubes comprising a "Salt-Bridge". The "Salt-Bridge" technique enables the electrodes to be placed in close proximity to each other in an extremely stable temperature and salinity environment. Electromechanical valves are used to switch the electrodes with respect to the salt-bridge arms permitting electrode offset voltage determination. An "AutoZero Circuit" measures and corrects for electrode offset to better than 10 microvolts.