New hydrostatic weighing apparatus for auto-density measurement of seven weights

A new hydrostatic weighing apparatus (HWA) is designed to load the weight of 1 g to 1 kg by using a loading plate which is made of a thin plate accurate in volume and mass. With this apparatus, the density of up to seven weights in the range of 1 g to 1 kg can be automatically measured in sequence. As a result of measurement, the uncertainty of 95% confidence level with k = 2 was 0.18 kg m−3 for 1 kg weight and 56 kg m−3 for 1 g weight. It was possible to measure the density of standard weights so that one can verify the E1 class weights within the maximum allowable error recommended by OIML. It was shown that major contributing factors of this apparatus to the uncertainty are volume of the loading plate, sample reading of the balance and reciprocal sensitivity of the balance.