Objects are examined with electric fields to determine properties of the objects. An active-plane (300) is defined by active electrodes (301-308) mounted on a dielectric-membrane (309). A processor energizes a first active electrode during a coupling operation and monitors a second active electrode. A cooperating plane (310) is defined by cooperating electrodes (321-329). The cooperating plane is displaced from the active plane and the processor selects electrical attributes (grounded, floating etc.) for selected cooperating electrodes during each coupling operation.