Stability and Performance of the Binary Compensation Unit for Cryogenic Current Comparator Bridges

As a key module of the redesigned cryogenic current comparator setup, the binary compensation unit is now in everyday use for resistance calibration at Physikalisch-Technische Bundesanstalt (PTB), as well as in a number of national metrology institutes. In a first step, its excellent performance was demonstrated in consistency checks involving the quantum Hall resistance and normal resistors with nominal values 100 Omega and 12.9 k Omega. Meanwhile, the stability of this compensation unit could be evaluated, too. Our analysis is based on the results of calibrations at regular intervals of 20 weeks covering more than three years. Also the influence of temperature has been studied experimentally. From the data presented here, we conclude that the device under test can be considered to be stable within 1 part in 10(4) over ten years.