This disclosure relates to a sensor for imaging boreholes with improved durability to impact along the wall of the borehole, which may protect the sensor from premature wear. Such an apparatus may include a housing, one or more button electrodes coupled to the housing, one or more current return electrodes couple to the housing, and a guard electrode disposed at least partly around the one or more button electrodes. The one or more button electrodes may transmit or receive an electrical or electromagnetic signal through the underground formation, and the one or more current return electrodes receive or transmit the signal. The guard electrode may block portions of the electrical or electromagnetic signal that did not pass through the underground formation. In addition, the guard electrode may include a number of holes to enable the guard electrode to couple to the housing while providing additional structural durability.