Operational Experience with a Cryogenic Volt Monitoring System

An experimental cryogenic measuring system, employing the dc and ac Josephson effects, which has been used to monitor the National Physical Laboratory maintained voltage standard is described in detail. Results obtained with this system over a period of 1 years are presented and compared with those from a system using room temperature potentiometry, which has already been described. Emphasis is laid on experience gained with cryogenic components of the system. The final section outlines a design for a portable Josephson apparatus based on experience with the present system, which would be capable of calibrating standard cells with maximum possible precision.