In the 1970s, NIST redefined the working volt using the Josephson effect, a phenomenon discovered by Brian Josephson in 1962. A Josephson junction generates an accurate voltage proportional to microwave frequency and fundamental constants. NIST researchers developed a four-junction array to maintain the U.S. legal volt by comparing its 10-millivolt output to 1-volt electrochemical cells.
Don Sullivan and Mogens Levinsen had a key insight: connecting multiple junctions in series could produce larger voltages without requiring precise current adjustment. This approach proved practical and eliminated the need for careful junction biasing, enabling more accurate voltage standards.
Keywords: Josephson, Junction, Standards
