Electrode Array of General Electrical Resistivity Survey

4P-VES electrode array includes Schlumberger and Wenner array. It is used to study the variation of resistivity with depth.

For Schlumberger array, potential electrodes M, N are located amidst current electrodes A, B symmetrically, and the origin O is the mid point of potential electrodes MN and current electrodes AB.

While Wenner array is a special case of Schlumberger array, that is, AM=MN=NB. Since AB/2=a, MN/2=b, and a=3b,