Figure 3
From: Resistivity Probability Tomography Imaging at the Castle of Zena, Italy
A sketch of the dipole-dipole electrode device for geoelectrical prospecting. A (positive) and B (negative) are the current electrodes to inject a current of intensity I into the ground. M and N are the potential electrodes to measure the voltage Δφ. The dipole length is a and k = 1, 2,... determines the spacing between the dipoles as an integer multiple of a.