Simple power measurement system

A simple power measuring system for low frequencies and sinusoidal conditions is described using commercially available instrumentation. It is composed of a phantom power source, current shunt, two sampling voltmeters and controlling computer. Power is calculated from measured voltage, current and phase of the phantom source. The uncertainty budget is evaluated after voltage and phase corrections are applied. Selection technique for current shunts as absolute current to voltage converters is proposed. Using such a system, an uncertainty of 60 /spl mu/W/VA was achieved.