Investigation of ac voltage measurement requirements for an oscillatory dynamic mode version of the watt balance

Recently a new form of the watt balance apparatus for measuring the Planck constant has been proposed that employs an oscillatory rather than a constant coil velocity during the dynamic mode of the experiment. The resulting AC voltage of frequency around 1 Hz and amplitude around 1 V would need to be measured to a relative standard uncertainty of better than 1 × 10^-8. A quantum voltmeter employing a programmable Josephson voltage standard and a sampling voltmeter with preamplifier is proposed to achieve this. This paper discusses some of the design issues involved with such a measurement.