The AC Josephson Effect Monitoring of the Unit of EMF in Canada

The experimental program outlined is directed toward the utilization of the ac Josephson effect to maintain surveillance of the unit of EMF in Canada. Preliminary results indicate a weighted mean value of 2e/h = 483 593.0 ± 0.2 (0.4 ppm) GHz/VNRc(73) which is, at present, not precise enough to detect the small drifts normally encountered in the mean value of the standard cell group upon which VNRC is based.