共查询到18条相似文献,搜索用时 218 毫秒
1.
为了探究压缩热效应对近单晶硅液体(DSL-2329)温度的影响,可采用理论推导与实验结果相结合的方式分析计算DSL-2329液体恒温压缩系数与恒熵压缩系数的比值,比值越大,则液体温度对压强越敏感。在0.1mK的恒温液体测量环境中,通过对液体温度与所受压强的微量调节,实现单晶硅球特定的3种悬浮状态,这3种状态之间包括液体密度分别在恒温与恒熵条件下的变化过程,利用这3种特定悬浮状态之间的压强关系计算出液体等温压缩系数与等熵压缩系数的比值。实验数据表明,压强变化量越小,测得的恒熵压缩系数与液体恒温压缩系数的比值与理论值0.72越接近。 相似文献
2.
3.
《计量技术》2017,(4)
介绍设计及构建的流量计现场检定方法及检定系统,在线检测被检定流量计内液体温度以及标准金属量器内的液体温度、液体密度、液体体积和几何中心处压力;计算标准金属量器内液体经过温度修正后的液体体积;检测在检测过程中挥发的油气体积及质量;计算实际液体质量或体积与被检定流量计现场示值的相对误差。检定系统包括控制器、数据采集单元、标准金属量器、高精度质量流量计、磁致伸缩液位传感器、温度传感器、密度传感器、压力传感器、溢流报警器和打印机。在标准金属量器的计量颈内安装高精度磁致伸缩液位传感器,用于测量计量颈处的液位高度,得出一定容积值,通过在线温度传感器的测量与修正,引入在线密度检测,检测精度和测量效率高。 相似文献
4.
5.
利用电容式传感器测量液位的研究 总被引:1,自引:0,他引:1
采用差动电容差压传感器测量液体的压力,利用液体的压力公式计算液位,设计了一种便携式低功耗液位仪。该仪器可以实现液位信号的采集和运算,同时还配有温度检测系统,通过软件编程对液位进行温度补偿,同时计算出液位值,最后结果由LCD显示。 相似文献
6.
7.
8.
利用PVT-100分析仅对几种不同牌号的流延聚丙烯(CPP)进行了pVT特性测量,得到了比容随温度和压力变化的关系.通过公式法计算出热膨胀系数α和等温压缩系数β与温度和压力的依赖关系,并与由Tait方程计算出的α和β结果进行了比较.另外从比容随温度和压力变化的关系图得到了各种牌号CPP熔融温度Tm与压力的关系。最后通过高温凝胶渗透色谱GPC法测量实验前后样品的分子量表明CPP在pVT特性测试过程中有部分降解。 相似文献
9.
为确定阿佛加德罗常数,意大利计量院(IMGC)和日本国家计量研究院(NRLM)分别建立各自的单晶硅球固体密度基准.本文介绍了两个硅球首次比对的结果NRLM以绝对法测量出IMGC硅球的质量和体积;IMGC采用液体静力法,通过比较两个硅球,测定NRLM硅球的密度.并且,双方还分别对IMGC硅球的直径进行了测量.测量结果的一致性很好密度不确定度<0.16×10-6,质量不确定度<0.1×10-6,体积不确定度<0.06×10-6,直径不确定度<0.04×10-6. 相似文献
10.
单晶硅球密度的绝对测量是阿伏加德罗常数测量的关键技术。综述了单晶硅球密度测量的最新进展,包括硅球密度测量的技术原理、测量领域、影响因素、测量装置及最佳测量能力等等,分析了硅球密度测量的主要难点和关键技术,预测了相关研究的技术前景及发展趋势。 相似文献
11.
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1 kg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。 相似文献
12.
Kenny M.J. Netterfield R.P. Wielunski L.S. Beaglehole D. 《IEEE transactions on instrumentation and measurement》1999,48(2):233-237
The Avogadro constant is required to be determined with an uncertainty of less than 1×10-8 in order to allow an atomic definition of the kilogram. A single-crystal silicon sphere 93.6 mm diameter is used for this determination. A thin surface layer (typically 2 nm to 5 nm thick on flats and 10 nm or more on spheres) of contaminants such as oxide, water and hydrocarbons on the sphere can significantly affect the measurements due to corrections for density changes and to phase change on reflection in the diameter measurement by optical interferometry. The stability of this surface layer as a function of time is also of importance because of ongoing measurements. The nature of this contamination has been investigated using optical ellipsometry and ion beam analysis. It is concluded that the composition and structure of the surface layer are affected by a number of parameters and that the most appropriate method of achieving the desired accuracy is to remove the surface layer by etching and to form a hard stable coating of controlled thickness and composition. This coating may be either silicon dioxide or silicon nitride 相似文献
13.
14.
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
15.
16.
研制了一套高精度的流体压力-密度-温度(p,ρ,T)测量系统,其适用温度、压力和密度范围分别为90—290 K,0—3 MPa,0—2 000 kg/m3。该系统基于阿基米德原理,采用单浮子磁选耦合力传递方法,实现密度的高精度测量。该系统的温度、压力测量标准不确定度分别为5 mK、250 Pa(1.5 MPa量程)/390 Pa(3 MPa量程),密度测量最大相对标准不确定度为0.1%。用新研制的密度测量系统,对190—276 K温度区间和0—3 MPa压力区间的甲烷气体密度进行了测量,实验结果与REFPROP密度值有较好的一致性,验证了该系统的可靠性。 相似文献
17.
Hiromichi Watanabe Naofumi Yamada Masahiro Okaji 《International Journal of Thermophysics》2004,25(1):221-236
As a part of the program to establish a thermal expansion standard, the linear thermal expansion coefficients of single-crystal silicon have been determined in the temperature range 293 to 1000 K using a dilatometer which consists of a heterodyne laser Michelson interferometer and gold versus platinum thermocouple. The relative standard deviation of the measured values from those calculated from the best least-squares fit was 0.21%. The relative expanded uncertainty in the measurement was estimated to be 1.1 to 1.5% in the temperature range, based upon an analysis of thirteen standard uncertainties. The present data are compared with the data previously obtained by similar dilatometers and the standard reference data for the thermal expansion coefficient of silicon, recommended by the Committee on Data for Science and Technology (CODATA). The present data are in good agreement with the most recently reported data but not with the earlier high-temperature data used to evaluate the standard reference data, which suggests a need for the reevaluation of the standard reference data for the thermal expansion coefficient of silicon at temperatures above 600 K. 相似文献
18.
《Advanced Powder Technology》2021,32(11):4222-4234
In this study, carbon spheres were synthesized from rice husk with hydrothermal carbonization method at different temperatures and different reaction times. Surface areas and pore size distributions of carbon spheres were characterized by BET surface area device, sphere morphology by SEM, structural characterization by FTIR-ATR and XRD, and thermal properties and degradation mechanism by DTA/TG. In addition, hydrogen gas adsorption measurements of the samples were also carried out with the Hiden IMI PSI gas storage device. It can be said that the required temperature is 280 °C and the required reaction time is 6 h in order to obtain homogeneous and ideal sphere morphology carbon spheres from a lignocellulosic biomass in experiments carried out under different conditions in an acidic reaction medium. This is clearly seen from the SEM images. In addition, FTIR spectra and XRD patterns confirm that the sphere was obtained. According to the BET surface area and pore size distribution results, it can be said that the main significant difference is in the mesopore structure of the carbon spheres, even if the surface area values of the samples obtained at different temperatures and different reaction times increase linearly with temperature. In order to determine the usability of carbon spheres obtained in different conditions in the energy field, the gravimetrically measured H2 storage capacities at cryogenic temperature (77 K) and pressure range of 0–30 bar were determined as maximum 1.1% by weight. When the hydrogen storage capacities of the samples are evaluated together with the BET surface area values and pore size distributions, it shows that the hydrogen storage capacity in carbon spheres is directly proportional to the mesopore volumes. In addition, Langmuir and Freundlich isotherms related to adsorption equilibrium were investigated in order to better define the H2 adsorption that took place in these samples. Considering the regression coefficients of the obtained isotherms, it was determined that some of the carbon spheres were more compatible with the Langmuir isotherm and some with the Freundlich isotherm. 相似文献