ESTABLISHED THE DENSITY STANDARD OF NATIONAL INSTITUTE OF METROLOGY (THAILAND)

摘要

The density standard in Thailand was established in 2007 in cooperation with NMIJ (National Metrology Institute of Japan). The main purpose is to serve the calibration demand of density equipment, which is constantly increasing in the industrial field. Hydrometer and solid density are the mainly used in this industrial field. Density hydrometer in the range of 600-2000 kg/m~3 with the highest scale division of 0.2 kg/m~3 was calibrated by using the hydrostatic weighing method (CUCOW's method) with the relative uncertainty of between 45 and 70 ×10~(-6). The silicon crystal ring is used as a density standard for measuring the density using the hydrostatic weighing method, the density of liquid was determined under the relative uncertainty of 24×10~(-6), which is the main source of overall uncertainties of hydrometer calibration. According to the procedure of measurement of working liquid density, the silicon ring was replaced by stainless steel and aluminum alloy work pieces in order to determine their solid density. The result of measurement relative uncertainty was about 35×10~(-6). This paper was summarizing all work which has been done by NIMT's density laboratory.