《JJG 795—2016耐电压测试仪检定规程》中几个问题的探讨

与《JJG 795—2004》相比,检定规程从耐压仪的准确度等级、设定电压和显示电压的检定、击穿报警预置电流和泄漏电流的检定,以及耐压仪输出容量的检定几个方面探讨了《JJG 795—2016耐电压测试仪检定规程》的变化,以及存在的问题。     

浅析燃油加油机检定过程中常见问题

按照JJG443-2006《燃油加油机检定规程》的规定,加油机的检定采用容量比较法,即将加油机示值与标准金属量器测得的加油机输出的实际容量进行比较,得出其相对误差。在实际检定中笔者发现,由于各种原因,直接影响到检定结果的准确性。下面针对加油机检定过程中常见问题作一些分析。     

关于JJG795-2016《耐电压测试仪检定规程》的探讨

本文介绍了新近颁布的JJG795-2016《耐电压测试仪》检定规程在贯彻执行时对输出电压检定及检定点选择、泄漏电流和击穿报警电流的检定、输出电压持续时间的检定的理解和探讨     

耐压测试仪检定中容易出现的几个问题

耐压测试仪检定时有3个重要参数：输出电压、击穿报警电流和电压持续时间。笔者认为，击穿报警电流和电压持续时间这两个参数的检定容易出现以下问题：     

加油机检定中油温测量常见问题分析与探讨

按照JJG443-2006《燃油加油机》检定规程的规定,加油机的检定采用容量比较法,即将加油机示值与标准金属量器测得的加油机输出的实际容量进行比较,得出其相对误差。温度对被测液体体积的影响较大,根据资料介绍,对汽油来说,     

JJG744-2004中关于摄片机检定的建议

JJG744—2004《医用诊断X射线辐射源》检定规程中关于摄片机的检定主要有辐射输出的质，辐射输出的线性、重复性，辐射野与光野一致性，X射线管的电压、电流、焦点及加载时间8个检定项目，其中X射线管的电流与加载时间两项指标要求首次检定时检．后续检定可不检。一般影响X射线摄片质量的主要因素有X射线管的有效焦点、辐射输出的质、辐射输出的重复性及线性等。     

耐电压测试仪输出交流电压示值误差测量值的不确定度评定

根据检定规程所规定的检定条件和检定方法,对耐电压测试仪输出交流电压示值误差的测量值进行不确定度评定。     

耐电压测试仪的击穿电流和容量测试法的研究

本文论述了在检定耐电压测试仪的击穿电流误差和容量时,设计出新的电阻器结构,同时满足这两项检定对电阻的阻值及负载能力的要求;在测试击穿电流时,也采取固定电阻,调节电压,使其与容量测试方法相同,达到减少测试设备数量和测试方法的相统一。     

直流稳压电源现场检定装置设计

本文主要介绍了直流稳压电源现场检定装置的组成及设计方案.通过设计直流电子负载、智能电网调整器、稳压电源自动检定装置,实现了直流稳压电源的电源电压调整率、负载调整率、输出电压短期稳定性、纹波电压、电压表、电流表示值误差的自动检定,提高了计量检定工作效率,解决了大功率直流稳压电源的现场保障问题.     

实施《JJG795-2004耐电压测试仪试行检定规程》的几点探讨

本文对于JJG795-2004《耐电压测试仪试行检定规程》中有关耐压测试仪输出电压、击穿报警电流误差及电压持续保持时间的检定方法谈几点探讨意见。     

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)。