An apparatus and method for measuring parasitic differences between dissimilar conductive paths on a semiconductor is provided. The apparatus provides a ring oscillator which has two propagation paths. The first path is traversed on a logical transition from low to high, and the second path is traversed on a logical transition from high to low. The gate stages for the first path may be interconnected via a metal conductive layer, and the gate stages for the second path may be connected to a dissimilar metal, or polycide, for example. A single output signal is produced which has a period equal to twice the delay of the inverter stages, plus any delay associated with the parasitic difference in the two paths. The duty cycle of the periodic signal may then be used to determine the parasitic difference between the two materials used to interconnect the stages in the ring oscillator.