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This paper summarizes the calibration of precision coaxial air lines in a 3.5-mm line size. The standard system of the National Metrology Institute of Japan (NMU) is used to accurately obtain mechanical measurements of the diameters and lengths of lines. Length compression of approximately 6.0 μm and diameter distortions caused by connections with specified torques have been observed in 3.5-mm air lines. A small insertion loss in the millimeter-wave frequency range has also been detected. Furthermore, NMIJ has established standards for scattering parameters in the frequency range up to 110 GHz for coaxial air lines in the 1.0-mm line size by the enhancement of mechanical measurement systems. [ABSTRACT FROM AUTHOR]

A new ac-dc comparator system of 20-1000 V has been developed at the National Metrology Institute of Japan (NMLJ) for the calibration of ac-dc thermal voltage converters (TVCs), which are used as national ac-dc transfer standards. The ac-dc transfer differences of high-voltage transfer standards were evaluated by a traditional step-up procedure. The voltage dependence of the ac-dc transfer difference was observed in the earlier step-up procedures over 300 V, as reported by the latest international intercomparison. The experimental results for high- voltage TVCs with several different range resistors at the NMU suggest that the voltage dependence may primarily be caused by input connectors of range resistors and the change in the resistance value of the resistor and TVC modules due to heating from resistors. This paper describes the voltage dependence improvement of ac-dc transfer differences over 300 V at the NMLJ. [ABSTRACT FROM AUTHOR]

An ac shunt calibration system at the National Metrology Institute of Japan (NMIJ) has been developed. The uncertainties of the system were estimated 3.4 \mu\Omega/\Omega for in-phase and 8.6 \mu\rad for quadrature at 55 Hz/5 A. Meanwhile, the enhancement of the system is planned up to 10 kHz/10 A. For this goal, the accuracy and high-frequency performance of the buffer amplifier, which have the largest influence on the uncertainties, have been improved by developing a load effect reduction (LER) circuit. The LER circuit cancels out the effect of output impedance of the buffer amplifier. The effect of the circuit on the buffer amplifier allows the uncertainties of the ac shunt calibration system to be reduced into 2.6 \mu\Omega/\Omega and 8.2 \mu\rad at power frequencies. [ABSTRACT FROM AUTHOR]

A fiber-based frequency comb has been developed to measure the frequency of a 633-nm iodine-stabilized laser at the National Metrology Institute of Japan (NMIJ). The measured frequency was consistent with the previous results measured with a Ti:sapphire-based comb. The NMLJ comb was shipped to Australia for the validation of the measurement capability of the National Measurement Institute, Australia (NMIA) and NMIJ combs using a common microwave reference and a common optical frequency. Consequently, the frequency consistency of the two combs was approximately 8 × 10-17. Furthermore, we demonstrate that an absolute mode number of the comb can easily and clearly be determined by using the two combs. [ABSTRACT FROM AUTHOR]

We present the results of a joint project to identify the origin of a discrepancy between the value of the Si lattice-parameter obtained by the Istituto Nazionale di Ricerca Metrologica and that obtained by the National Metrology Institute of Japan. The re-evaluation of diffraction in the laser interferometry indicates that misalignment of the interfering beams could account for the observed difference. [ABSTRACT FROM AUTHOR]