OhmCorr™ has two probes spaced 1.97" (5cm) apart which are placed in holes drilled to a depth of 3/8th" (8mm) and filled with conductive gel. The direct digital read-out of resistivity is displayed on the LCD when the control switch is activated. OhmCorr™ and CorMap™, when used together, provide an economical and sound diagnostic system of corrosion in reinforced concrete.