Various embodiments include planar sensor arrays for use in determining characteristics of a material under test (MUT). The planar sensor arrays can include a set of electrodes positioned to enhance a depth and clarity of detection into the material under test. Some embodiments include an electromagnetic sensor array having: a first set of two rectilinear electrodes, positioned opposed to one another across a space; and a second set of two rectilinear electrodes, positioned opposed to one another across the space, the second set being off-set from the first set, wherein the first set and the second set are configured to detect an electromagnetic impedance of the MUT.