Voltage calibration systems using Josephson junction arrays

The authors review the fundamentals of Josephson voltage standards and show how computer control makes these standards simple to use in a variety of applications. It is noted that the accuracy and stability of voltage standards based on the Josephson effect far surpass those of all other voltage-standard devices. The voltage generated is independent of environmental and material characteristics because it is based on a fundamental constant, the ratio of the elementary charge to Planck's constant. International agreement on the value of this constant ensures uniformity and reproducibility throughput the world. In 1990. there are about 25 laboratories in the world with Josephson voltage standard systems. These systems realize the intrinsic definition of the volt with an accuracy that is far above what can be achieved with transfer standards.<>