DC AND AC TECHNIQUES FOR RESISTANCE AND IMPEDANCE MEASUREMENTS

Techniques related to the establishment and the comparison of primary standards of resistance and capacitance are described and discussed. In the field of resistance, the characteristics of primary standard resistors of 1-OMEGA and 10000-OMEGA are presented and dc resistance-ratio measurement techniques reviewed, including the series-parallel method, the Warshawsky bridge and the cryogenic current comparator bridge. A review of techniques and results regarding very low-frequency ac measurements of dc standard resistors is also given. In the field of capacitance, the realization of the farad using calculable standards is discussed as well as the techniques for accurate measurements of four terminal-pair impedances used in particular for linking the farad and the ohm.