共查询到19条相似文献,搜索用时 187 毫秒
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在进行质量量值传递时,空气浮力修正成为重要的影响量。本文通过对空气中质量测量的基本原理分析和折算质量计算公式推导,推导出空气浮力修正因子。文中进行了空气浮力因子的数值模拟,通过数值模拟曲线分析出空气浮力修正因子的影响,并在曲线图上便捷的查出空气浮力修正因子,直接应用于砝码折算质量的计算。 相似文献
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对于准确度等级高的砝码在进行折算质量的不确定度评定时,要考虑空气浮力修正,如果空气浮力小于被测砝码最大允许误差的九分之一时,可不进行空气浮力修正,而将其放人空气浮力不确定度进行计算。 相似文献
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0引言用于检定砝码的电子天平如何选择?主要考虑何种技术参数?参数应满足何种要求?JJG99-2006《砝码》检定规程中规定:在测量砝码质量选择衡量仪器时,衡量仪器的计量特性在进行测量之前要已知。如果被检砝码进行空气浮力修正,则其合成标准不确定度不得超过被检砝码质量最大允许误差绝对值的六分之一;如果被检砝码不进行空气浮力修正,则合成标准不确 相似文献
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从砝码允差表中不难看出,毫克组(1mg~500mg)砝码有一个特点:它们的检定精度相同。由于有这样一个特点,使得判定是否应进行空气浮力修正问题变得非常简单。在砝码检定规程(JJG99—81)中规定:“在检定砝码时,由于空气浮力所引入的误差不得超过该砝码检定精度的五分之一,否则,必须对空气浮力进行修正。”即进行空气浮力修正的条件为: 相似文献
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Patrick J. Abbott Zeina J. Jabour 《Journal of research of the National Institute of Standards and Technology》2011,116(4):689-702
Vacuum weighing of mass artifacts eliminates the necessity of air buoyancy correction and its contribution to the measurement uncertainty. Vacuum weighing is also an important process in the experiments currently underway for the redefinition of the SI mass unit, the kilogram. Creating the optimum vacuum environment for mass metrology requires careful design and selection of construction materials, plumbing components, pumping, and pressure gauging technologies. We review the vacuum technology1 required for mass metrology and suggest procedures and hardware for successful and reproducible operation. 相似文献
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为了克服单晶硅球密度测量静力称重法精度受液体表面张力的影响,研究了压浮法进行单晶硅球密度精密比较测量方法和测量系统。在一定的温度下,调节压力,利用液体压缩系数控制液体密度使标准单晶硅球和被测单晶硅球稳定悬浮于工作液体中,通过温度、压力和悬浮高度的测量,计算出二者之间的密度差值。通过双层控温系统保证了液体温度长期波动在±0.25 mK内,利用标准单晶硅球在不同温度-压力悬浮条件线性关系计算出液体压缩系数。试验证明,压浮法测量装置实现了单晶硅球密度差值的精密测量,标准测量相对不确定度为2×10-7。 相似文献
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In general mass measurements are carried out in air and that’s why air buoyancy correction plays a major role in mass measurements and it is totally dependent on density of air of the laboratory during the measurement. The density of air is calculated from temperature, relative humidity, air pressure, concentration of CO2 monitored (for CIPM formula only) in the laboratory rather direct determination and for calculation of density of air, CIPM-2007 formula is recognized as most accurate formula. Since CIPM formula is very complicated formula and it is not required for less accurate measurements, different National Metrology Institutes have derived simple equations to calculate air density and those are known as approximation formulas. We had gone through a comparative analysis among different formulas of density of air to evaluate which approximation formula is most accurate compare to CIPM-2007 formula. 相似文献
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For a new determination of the Avogadro constant using small crystals of isotopically enriched silicon, the density of a sample was determined at Physikalisch-Technische Bundesanstalt. The sample has a mass of 58 g and a 28Si enrichment of about 99.98%. Its density was compared by the pressure-of-flotation method to the density of a large hollow transfer standard that was manufactured from natural silicon, to have the same density. The flotation measurement yielded a relative density difference of 0.64(10) 10-6. The density of the transfer standard was then measured by hydrostatic weighing, which is traceable to a primary density standard. Thus, the density of the small 28Si sample was determined to be 2320.08031(40) kg/m 3, i.e., with a relative standard uncertainty of 0.17 10-6 相似文献
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