Abstract: An improved electrode construction for apparatus for testing the integrity of thru-hole plating in printed circuit boards and the like by measuring the effective thickness thereof. A first conically shaped electrode assembly is adapted to be displaced along a predetermined path into engagement with one of the defining marginal perimetric edges of a plated thru-hole in a circuit board. A second and complementally shaped electrode assembly is adapted to be displaced into engagement with the other defining marginal perimetric edge of the thru-hole. Each of such electrode assemblies includes a pair of discrete selectively contoured electrode elements adapted to make line contact with the marginal defining edges of the thru-hole, whereby a predetermined magnitude of constant current can be passed through the plating intermediate one pair of electrode elements, and the voltage drop developed thereby across the thru-hole plating measured by the other pair of electrode elements.