According to one aspect, embodiments herein provide a PVR comprising a resonator having an oscillation frequency, the resonator comprising at least one proof-mass, a mechanical reference, at least one drive plate located adjacent a first side of the at least one proof-mass, and at least one sense plate located adjacent a second side of the at least one proof-mass, a voltage source coupled to the drive and sense plates, a reference oscillator configured to provide a reference signal having a reference frequency to the voltage source; and an output, wherein the voltage source is configured to provide a bias voltage signal to the at least one drive and at least one sense plates of the resonator to drive the oscillation frequency of the resonator to match the reference frequency, and wherein the bias voltage signal is also provided to the output of the PVR as a voltage reference signal.