—We consider the ranges of current and voltage values for laterolog tools. It is shown that expansion of the dynamic range of these parameters is possible by mathematical focusing and digital filtering and by fulfillment of the conditions for the effective number of bits and by compliance with the tool requirements. The principles of mathematical focusing are considered by the example of the 5BK tool designed by AO NPF Geofizika (Joint-Stock Company) in Ufa. The digital-filtering calculation and application technique is described. The results of well tests are presented.