Progress in Resistance Ratio Measurements Using a Cryogenic Current Comparator at LCIE

The cryogenic current comparator (CCC) built at LCIE allows measurement of resistance ratios equal to ??(1 ?? 4 ?? 10-5) where ?? = 1, 10, 100, 64.53, or 129.06. The equipment is now currently used for intercomparison of 1-?? standard resistors with a typical standard deviation of 5 ?? 10-9 (one single observation) and for calibration of 10 000-?? resistors in terms of 1-?? resistors with a standard deviation of 2 ?? 10-8 (1 single observation). Comparison of the 100/1 (or 10/1 ?? 10/1 ratio of the CCC with the ratios of Hamon-type series parallel dividers is reported. The agreement between these different ratios is better than 1 ?? 10-8.