用于量值传递的高精度单晶硅球质量测量研究

基于单晶硅球与现行常用砝码的物理特性差异,提出空气浮力修正改进计算方法。通过对硅球质量测量时空气密度瞬态变化分析,得出单次测量序列中存在6种不同空气密度变化序列,根据不同精度等级测量对各环境参数变化限值的要求,利用CIPM公式计算环境条件动态变化下的空气密度变化量,分析得出即使在恒温恒湿精密实验室下开展测量,相邻2次测量间由于环境参数变化带来的空气密度变化幅度可达1×10^-4kg/m3。并以铂铱合金砝码作为参考砝码开展对标称质量值为1kg的高精度单晶硅球进行质量测量时,通过实验验证测量环境空气密度在单个测量序列中产生浮动变化时,采用改进后的空气浮力修正算法可减少15.1～30.2μg的计算误差。

Research on High Accuracy Mass Measurement of Silicon Sphere in the Dissemination of Mass Unit

Based on the differences on material and geometry properties among silicon spheres and other regular mass standards,an improved method to determine the air buoyancy correction in the silicon sphere mass measurement was proposed. Six types of air buoyancy fluctuations were concluded by studying the real-time data of air density during the mass measurement of silicon sphere. Since the environment conditions are changeable,it was observed that the air buoyancy fluctuations of 1 × 10^-4 kg/m³ were existed between any two adjacent weighing processes in mass measurement of silicon sphere. About 15. 1 ~ 30. 2 μg errors in the air buoyancy correction can be produced by ignoring the air density fluctuation in the mass measurement of a 1 kg silicon sphere( using a 1 kg platinum-iridium weight as reference standard).