HR: 0802h
AN: NS11C-0696    [Abstracts]
TI: Building Better Electrodes for Electrical Resistivity and Induced Polarization Data
AU: Adkins, P L
EM: padkins@mpt3d.com
AF: Multi-Phase Technologies, LLC, 420 S. Rock Blvd, Sparks, NV 89431, United States
AU: * La Brecque, D J
EM: dlabrec887@yahoo.com
AF: Multi-Phase Technologies, LLC, 420 S. Rock Blvd, Sparks, NV 89431, United States
AB: In the third year of a project to understand and mitigate the systematic noise in resistivity and induced polarization measurements, we put a significant effort into understanding and developing better electrodes. The simple metal electrodes commonly used for both transmitting and receiving of electrical geophysical data are likely the Achilles" heal of the resistivity method. Even stainless steel, a commonly used electrode material because of its durability, showed only average results in laboratory tests for electrode noise. Better results have been found with non-polarizing metal-metal salt electrodes, which are widely used as surface electrodes and in IP surveys. But although they produce small measurement errors, they are not durable enough for in-situ borehole resistivity surveys, and often contain compounds that are toxic to the environment. They are also very seldom used as transmitters. In laboratory studies, we are exploring other materials and configurations for low-noise compound electrodes that will be nontoxic, inexpensive, and durable and can be used as both transmitters and receivers. Testing of the electrical noise levels of electrodes is an arduous task involving repeated measurements under varying conditions at field scales. Thus it is important to find methods of sorting out likely candidates from the mass of possible electrode configurations and construction methods. Testing of electrode impedance versus current density appears to provide simple criteria for predicting the suitability of electrodes. The best electrodes show relatively low overall contact impedance, relatively small changes in impedance with increased current density, and relatively small changes in impedance with time. Furthermore it can be shown that resistivity and induced polarization performance of electrodes is strongly correlated, so that methods of finding electrodes with low impedance and good direct current performance usually provide better quality induced polarization data and vice- versa.
DE: 0694 Instruments and techniques
DE: 0994 Instruments and techniques
DE: 1895 Instruments and techniques: monitoring
SC: Near-Surface Geophysics [NS]
MN: 2007 Fall Meeting