An electrode array is a configuration of electrodes used for measuring either an electric current or voltage. Some electrode arrays can operate in a bidirectional fashion, in that they can also be used to provide a stimulating pattern of electric current or voltage. Common arrays include: * Schlumberger (Wenner) * Wenner alpha * Wenner beta * Wenner gamma * Pole-pole * Dipole-dipole * Pole-dipole * Equatorial dipole-dipole