Accuracy of measurements of the quantized Hall resistivity by a direct current comparator type potentiometer: calibration using a Josephson potentiometer

The accuracy of measurements of the quantized Hall resistivity (QHR) by a direct-current-comparator (DCC)-type potentiometer is estimated based on a linearity calibration of the potentiometer using a Josephson potentiometer. The power coefficient contribution to the nonlinearity of the DCC potentiometer was found to be 0.15+or-0.02 p.p.m./(100 mV)/sup 2/ at 18.5+or-0.5 degrees C in 1985 and 0.21+or-0.03 p.p.m./(100 mV)/sup 2/ at 20.5+or-0.5 degrees C in 1988. The possibility of accurate measurements of the ratio QHR/R/sub STD/ with uncertainties less than 0.05 p.p.m. by the DCC potentiometer is discussed.<
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