Reassessment of a Determination ofeh, Using Macroscopic Quantum Phase Coherence in Superconductors

The discovery of a possible systematic error in the Parker-Langenberg-Denenstein-Taylor determination of $\frac{e}{h}$, using the ac Josephson effect, has led to a remeasurement together with a reassessment of the original data. A number of factors contributing to the experimental uncertainty were carefully reexamined. The result of the remeasurement is in good agreement with the result reported by Parker et al. A comparison of the present result with the result of a reanalysis of the data Parker et al. indicates that the suspected systematic error, if present in the earlier experiment, is almost certainly less than 2 parts per million.