直流电阻箱两种测量方法的不确定度评定

文章从测量方法、数学模型、不确定度来源等方面入手阐述了分别用8508A数字多用表直流电阻档做标准和用QJ48直流比较电桥做标准校准直流电阻箱时,如何对直流电阻箱示值误差的测量结果进行不确定度评定。     

直流比较电桥标准装置测量不确定度评定报告

主要论述在执行JJG982-2003《直流电阻箱检定规程》时,采用QJ48型直流比较电桥检定0.01级直流电阻箱时,对其测量结果进行测量不确定度评定的方法。     

直流电阻箱测量结果的不确定度评定

文章对直流电阻箱示值误差测量结果的不确定度做了详细评定,可作为用数字多用表检定直流电阻箱的一个典型实例参考。     

Excel在一种直流电阻箱检定装置不确定度评定中的应用(一)

直流电阻箱的检定通常使用高等级的直流比较仪式电桥或直读电桥等，这些设备操作复杂、费时费力。随着高稳定度恒流源的出现和直流数字电压表的应用，直流电阻箱的检定变得简单方便。但是，直流电阻箱的等级是按相对误差确定的．而数字表的允许误差是由两部分组成：一部分与读数成线性关系；另一部分与量程有关。另外，在测量大阻值电阻上的电压时，数字表的输入阻抗将带来较大的误差。为此，需要对测量不确定度进行详细的评定，从而确定一个满足检定不确定度要求的最佳方案。本文将Excel运用到测量不确定度的评定计算中，从而很方便地实现了对每一测量点的测量不确定度进行评定。     

电阻箱检定时测量不确定度的评价

介绍了用QJ48型直流比较电桥装置检定电阻箱时，测量标准不确定度的分析和评价过程；讨论了影响评价结果不确定度的几个主要来源；通过一组实例，给出了电阻箱检定不确定度的分析和评价结果，该过程和结论可应用在对于计量标准进行相应指标的不确定度分析上，也可用于估计电阻箱检定本身的不确定度。     

直流电阻箱示值误差的测量不确定度评定

本文采用高精度数字万用表直接测量法校准电阻,对直流电阻箱示值误差的测量不确定度进行评定,建立了不确定度评定的数学模型,分析了测量过程中存在的不确定度来源,并量化不确定度分量,从而求出合成不确定度和扩展不确定度.     

直流电桥示值误差测量结果的不确定度评定

文章以直流电桥检定装置之主标准直流电阻箱z×78对直流单臂电桥QJ23检定为例,进行示值误差测量不确定度评定.     

直流电阻箱检定设备比对及其不确定度分析

分别采用数字多用表和全自动电阻校验装置检定同一被测电阻箱,通过比对试验客观掌握直流电阻箱检定装置现状,确保量值准确统一可靠,并对测量结果进行不确定度分析。     

用数字表8846A检定直流电阻箱

测量直流电阻箱,如果直接用数字表的电阻测量功能,则对数字多用表的测量不确定度要求比较高,如果利用转换开关分别对被检电阻箱和标准电阻进行不同步测量,处理数据又很复杂。     

直流电阻箱测量结果不确定度的评定

本文介绍了直流电阻箱测量结果不确定度的评定方法。     

Estimation of Parameters of Universal Distribution of Moments of Failure of Products

A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling.     

Evaluation of optical properties of highly scattering media by moments of distributions of times of flight of photons

A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue.     

Estimation of potentialities of methods of summation of direct measurement errors

Conventional methods for summation of direct measurement errors are considered. Conditions under which these methods provide consistent results are stated. It is proposed to utilize for characteristic of the total error, its interval estimator or the half-sum of the value obtained by adding up its arithmetic and geometric random errors.Translated from Izmeritel'naya Tekhnika, No. 4, pp. 10–12, April, 1995.     

空压机轴承箱蜗壳温度探头油封改造

由于空压机进气侧轴承箱蜗壳温度探头密封效果不好,使空压机及其后续管道受到油污染。后将温度探头的O形圈密封改为骨架油封,杜绝了轴承箱漏油问题。文章简介空压机的结构和技术参数,详细介绍了骨架油封的制作和优点。     

Characteristics of mechanical properties of materials in studies of conditions of attainment of marginal states

It is shown that conditions of attainment of marginal states in the material of structural components are formulated on the basis of analysis of force and deformation criteria of formation and development of destruction. The parameters of these criteria are data on types of structural materials, standard and special characteristics of their mechanical properties, structural forms of considered elements of the equipment, and their operating stress loading. In this case, the construction of a system of state equations for describing interrelation of current damage, external actions, and responses to them is based on the concept of calculating variations in properties of materials at all stages of the design life cycle.     

Determination of parameters of microstructural inhomogeneity of deformation of metals by the method of modeling

The article suggests a method of evaluating the microstructural inhomogeneity of deformation of metals by modeling. The method includes the measurement of deformations of metal according to meshes of a dividing grid with small base and the calculation of the distribution parameters of microdeformations in model representation. It is shown that the modeling method makes it possible objectively to evaluate the microinhomogeneity of deformation of metals independently of the chosen mesh size of the dividing grid. New structural characteristics are introduced: the base and wave of variation expressing the degree of crumbling or amalgamation of metal grains by inhomogeneity of deformation.Translated from Problemy Prochnosti, No. 7, pp. 40–44, July, 1991.     

Analysis of the rate of propagation of the wave of change of boiling modes

An approximate analytical expression is derived for the velocity of the front of the wave of change of boiling modes on a rod and on a plate. The impact of the Thomson effect and of the heater orientation in the gravity field is included. Adequate agreement is demonstrated between the derived relations and experimental data.     

水三相点复现的不确定度评定

水三相点是开尔文热力学温度的唯一基准点，也是ITS-90国际温标重要的定义固定点。因此，水三相点不确定度分析对整个温标的建立、温度量值传递起着至关重要的作用。近3年来，中国计量科学研究院研制出一系列高质量的水三相点容器，加强了水三相点的研究，为不确定度的分析提供了更为可靠的实验依据。同时，不确定度的分析也是客观评价新研制容器性能的一个重要指标。因此，根据实验结果对新研制容器所复现的水三相点进行了不确定度评定。评定结果表明，其扩展不确定度为0．16mK(k=2．69，P=0．99)。