The Josephson Effect and Voltage Standards

Josephson voltage standards with series arrays of up to 20 000 tunnel junctions can generate stable reference voltages at arbitrary values between - 15 V and + 15 V. These standards, which are now installed in many national and industrial laboratories, are used to calibrate Weston cells or Zener reference standards, to measure the linearity of digital voltmeters, and as precise potentiometers for the measurement of voltage and resistance ratios. The fundamental principles, the historical development, the design, the fabrication and the operation of these voltage standards are reviewed.