In this paper, an analysis of the unsteady laminar flow in a cone-and-plate system where the angular velocity of the cone is modulated sinusoidally with time is performed. This is used to test the frequency response of circular or rectangular electrochemical sensors embedded flush with the plate plane. By using different viscosities, it is possible to separate experimentally the effect of the hydrodynamic transfer function between the angular velocity and the velocity gradient at the plate from the effect of the frequency response of mass transfer probes between the velocity gradient and the instantaneous limiting current. Excellent agreement between theory and experiment is found in the frequency range of interest for both circular and rectangular probes.