Evaluation of automatic sub-multiple mass calibration for sub-milligram weights at NMIJ

Abstract

Mass standards are essential for the precise measurement of mass. Due to the increasing demand for small mass measurements, it is essential to be able to disseminate the sub-milligram mass standard from the National Metrology Institutes. Recently, the National Metrology Institute of Japan has developed an apparatus for mass calibration of sub-milligram weights by automatically transporting the weights. Consequently, the masses of the weights can be calibrated accurately and reliably. Sub-multiple calibration is often used for accurate mass calibration of weights smaller than 1 kg. In this study, by combining this method with the developed apparatus, the mass calibration uncertainty of sub-milligram weights was improved. The mass calibrations of 0.1 mg, 0.2 mg, and 0.5 mg weights were performed with standard uncertainties of 0.019 µg, 0.023 µg, and 0.040 µg, respectively. These uncertainties were smaller than the calibration uncertainties obtained by manually transporting sub-milligram weights to an ultra-micro balance.