Assessment of errors from different electrode materials and configurations for electrical resistivity and time-domain IP data on laboratory models

In the last twenty years Electrical Resistivity Tomography and time-domain Induced Polarization techniques have been widely used for geological, environmental, chemical and hydro-geological applications. As a matter of fact, the choice of electrodes (material and number) to be employed is crucial to avoid large measurement errors. The aim of this work is the quantitative assessment of errors in acquisition with respect to different electrode materials and configurations, as well as a comparison with previous results. To this end, a cylindrical column (height of 280 mm, diameter of 135 mm) is set up and all measurements are performed on a 7 electrode, 2D horizontal cross-section. Resistance, chargeability and self-potential measurements for different electrode materials (steel, iron, aluminium, copper and carbon) are acquired over a cylindrical sample filled by water with known conductivity. A statistical analysis of the experimental data demonstrates that iron and steel provide the best performances both for resistance and for chargeability. Carbon and copper are reliable for resistive surveys, but not for capacitive ones. Standard deviations associated to aluminium electrodes are the highest among the five materials. Changing the number of electrodes (from 7 to 20) results in an exponential increase of resolution of the resistive and chargeable anomalies included in the samples.