Improvements on the design of a four terminal-pair coaxial bridge

This paper describes how recent modifications made at the four terminal-pair coaxial bridge (4TCB), in operation at Inmetro, have improved the coaxiality of the bridge, significantly reducing the net current in the coaxial cables, thus reducing both electromagnetic noise and possible systematic errors. This has improved the reliability and repeatability of impedance measurements, and has enabled us to achieve uncertainties as low as parts in 10⁸.