Influence of inductive coupling between leads on resistivity measurements in multilayer soils

A detailed study of the influence of inductive coupling between current and potential leads on soil resistivity measurements has been carried out. Two commonly used measurement arrangements, Wenner and Schlumberger, are modeled and analyzed at different frequencies and for different soil structures. The study quantifies the coupling between current and potential leads for typical separation distances between the leads for uniform and multilayer soils. The results show that high operating frequencies or small separation distances between leads result in high inductive coupling levels, as expected. The study also shows that when the resistivity of a uniform soil or the bottom layer resistivity of a multilayer soil is low, the measurement error caused by the inductive coupling is large. Coupling levels presented in this paper can be used as a reference to estimate possible errors in soil resistivity measurements.