US Patent 7683650 Measurement instrument with synchronized interference signals

An instrument for measuring electrical parameters includes a measurement section having a measurement aperture; and a support section providing at least one of power and digital control for the measurement section. The support section has an interference signal frequency, wherein the interference frequency is an integer multiple of the reciprocal of the measurement aperture and the measurement aperture and the interference signal are phase-locked. As a result, the effect of the interference signal on electrical parameters measured is minimized.