钳形接地电阻测试仪校准的新方法

本文介绍了钳形接地电阻测试仪的原理,设计了一种结合标准电阻器法和电流电压法,完成对钳形接地电阻测试仪进行校准的新方法,并能实现对钳形接地电阻测试仪电流表的校准。     

钳形接地电阻测试仪的应用与局限性分析

本文简单介绍了钳形接地电阻测试仪（以下简称钳表）的测量原理。通过在一般建筑物防雷检测和油罐区防雷检测工作中的实际运用,分析钳表对比普通接地电阻测试仪的优越性和局限性,探讨钳表的测试方法和计算方法。     

钳形接地电阻测试仪校准方法探讨

钳形接地电阻测试仪是用来测量任何有回路系统之接地电阻值,在国外已成功应用多年,由于其测量方法简便,重复性好等优点,近年来在我国逐步地推广使用,目前我国还没有正式发布的校准规范。本文经过实际工作的实践,提出了钳形接地电阻测试仪的校准方法供探讨。     

双钳接地电阻测试仪校准方法的研究

本文介绍了双钳接地电阻测试仪的工作原理,讨论了双钳接地电阻测试仪的校准方法并给出了不确定度的评定。     

输电线路杆塔接地电阻测量方法研究

由于杆塔接地极对地电阻存在问题、杆塔连接螺栓处严重锈蚀导致接触电阻很大;更严重的已形成开路;靠近地面的接地线部分在电化学腐蚀的作用下接地线变细,甚至断裂。所以输电路杆塔接地电阻的测量十分重要。本文介绍了摇表、钳形接地电阻测试仪。对测试输电线路杆塔接地电阻时的工作原理进行分析,通过数据进行比较两种测试方法的不同,然后介绍了两种测试方式的联系以及注意事项,以便在输电线路杆塔接地电阻测量中能够更好的使用仪器使测量更准确。     

JJG1054-2009《钳形接地电阻仪》检定规程解读

一、制定背景 钳形接地电阻仪是传统接地电阻测量技术的重大突破,在国内外生产和使用已有十几年,我国于2001年开始生产。测量方法与接地电阻表所采用方法完全不同,在测量有回路的接地系统时,不需辅助电极,不需将接地体与负载隔离,只需将被测接地线置于钳口几何中心位置,即可从液晶屏上读出接地电阻值,实现在线测量。因此,钳形接地电阻仪广泛应用于电力、气象、电信、油田、建筑及工业电气设备的接地电阻测量。     

浅析利用钳形地阻表测量架空线路杆塔接地电阻的正确方法

随着电力系统的不断发展壮大和完善。架空线路杆塔接地电阻是否满足要求是网络安全运行的重要保证,定期测量架空线路杆塔接地电阻是有效的维护方法之一。本文主要分析了钳形地阻表测量架空线路杆塔接地电阻的一些正确方法。     

接地电阻测量技术在牵引变电所的应用

分析伏安法、ZC-8型接地电阻测试仪测试法、三极法等测量接地网的原理及其局限性,利用FET-3数字式地网电阻测试仪测量接地电阻的原理、测试方法,来提高牵引变电所接地电网电阻的准确性.     

接地导通电阻测试仪测量不确定度评估

接地导通电阻测试仪是用于测量交流电网供电的电器设备(如家用电器、电动电热器具、医用电气设备及测量、控制和试验室用电气设备)的可触及金属壳体与该设备引出的安全接地(线)之间导通电器的电阻。文章介绍了接地导通电阻测试仪测量不确定度评估,为接地导通电阻测试仪测量不确定度测量不确定度的评估起到模板作用。     

数字式钳形接地电阻仪测量结果不确定度评定

一、概述1.测量依据JJG1054-2009《钳形接地电阻仪》检定规程。2.环境条件温度:(20±5)℃,湿度:(40～75)%RH。3.测量标准接地电阻仪检定装置(以下简称"检定仪"),型号:JD-1B,测量范围:(0.001～1000)Ω,MPE:±0.1%。4.被测对象数字式钳形接地电阻仪(以下简称"钳阻仪"),型号:ETCR2000B,测量范围:(0.01～1000)Ω,MPE:±(1%～20%)。5.测量方法利用标准电阻器法,用钳阻仪钳住检定仪输出端的连接导线,连接导线应置于近似钳头几何中心位置,并与钳圈垂直。按钳阻仪选取的检定点调节检定仪的电阻值,     

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.     

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.     

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.     

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)。