Development of a 60 Hz power standard using SNS programmable Josephson voltage standards

We are implementing a new standard for 60 Hz power measurements based on precision sinusoidal reference voltages from two independent programmable Josephson voltage standards (PJVS): one for voltage and one for current. The National Institute of Standards and Technology PJVS systems use series arrays of Josephson junctions to produce accurate quantum-based dc voltages. Using stepwise-approximation synthesis, the PJVS systems produce sinewaves with precisely calculable rms voltage and spectral content. We present measurements and calculations that elucidate the sources of error in the rms voltage that are intrinsic to the digital-synthesis technique and that are due to the finite rise times and transients that occur when switching between the discrete voltages. Our goal is to reduce all error sources and uncertainty contributions from the PJVS synthesized waveforms to a few parts in 10⁷ so that the overall uncertainty in the ac-power standard is a few parts in 10⁶.