In a non-destructive, production-oriented technique for measuring an electrical characteristic of a material, a first nonconductive flexible sheet having a first conductive pattern thereon is pressed against a portion of the surface of the material, and a second nonconductive flexible sheet having a second conductive pattern thereon is pressed against another portion of the surface of the material. An electrical signal is applied between the two patterns and the effect of the material on the signal is measured to obtain a desired electrical characteristic of the material. The method and apparatus are particularly useful for measuring, at microwave frequencies, the propogation velocity factor and dielectric constant of substrates for use in thin film microwave circuits. For such measurements, the first and second conductive patterns advantageously comprise a resonant circuit and a ground plane. The measurement is made by applying a swept frequency signal to the resonant circuit while simultaneously monitoring reflected power from the resonant circuit.