A bilateral comparison of measurement of diameters and characteristic impedance of precision 3.5 mm coaxial air lines

This paper summaries a bilateral comparison of measurement of the diameters of two precision 3.5 mm coaxial air lines. These mechanical measurements were made independently by two national metrology institutes: NMIJ and NPL. The laboratories also calculated the characteristic impedances based on the measured diameter values. The difference between the characteristic impedances calculated by the two laboratories for both lines was less than 0.02 Ω. The uncertainty of this difference at a 95 % level of confidence, for each line, was 0.08 Ω and 0.31 Ω.