电阻变化法测量绕组温升的探讨

绕组温升是安全标准中的一项重要指标。因导体电阻随温度变化呈现某一规律,所以,测试出断电瞬时的电阻值就可推算出绕组温升。由于绕组断开电源后,温度逐渐下降,所以测得的电阻值并不是绕组断电瞬时的电阻值,我们可以通过短时间间隔读取的电阻测量值,利用作图法和回归分析法来确定断电瞬时的电阻值,从而推算出绕组温升。     

绕组温升测量结果不确定度的评定

在电器产品的安全型式试验过程中,一般会采用电阻法测量绕组的温升,但该方法需要测量的数值较多且计算的公式也较复杂,这给测量结果的不确度评定带来了一定的难度。本文以风扇电机绕组温升测量结果不确定度评定为实例,详细介绍了此类测量结果的不确定度评定过程和计算方法,以供试验人员参考。     

双目动态摄影测量技术研究与实现

针对振动条件下雷达天线型面变形测量问题,设计了基于双目视觉动态摄影测量系统.介绍了系统的组成和工作流程,并对其中的相机同步技术、相机控制场标定技术、圆形标志点中心定位技术、像点自动匹配技术进行了研究.系统通过图像采集卡实现了一种廉价的ns级双相机同步方式.用10参数模型对相机进行了标定.采用了一种高反射率的圆形人工标志,通过Canny灰度质心的方法实现了圆形标志点中心的定位.系统用两种方法实现了像点的自动匹配:第一种是基于待测物体近似坐标的驱动点匹配方法.第二种则是运用核线约束、像点残差约束和相对关系约束,完成像点自动匹配.进行了振动测量试验,试验结果表明在物距为1.5 m和物体振动频率小于50 Hz条件下,系统点位测量精度小于0.3 mm,平面度测量精度小于0.1 mm.     

弧焊电源变压器绕组温升快速测量的新方法

针对弧焊电源主器绕组温升检测需要进行绕组电阻值精确测量的问题，本文在恒温源法和双臂电地的基础上，利用计算机速测试物特性，提出了比较法的测量方案，由于孤焊电源器绕组可等效为电感Ｌ与电阻Ｒ的率联电路，当一恒流流过时，电流达到稳定的时间较长，根据阻尼振荡的大批量，Ｒ－Ｌ与一电容Ｃ构成欠阻尼的二阶系统，可使由电感引起的过渡过程的稳定时间缩短在一秒钟以内，从而实现了对绕组温升的快速，准确测量。     

Indoor GPS工业测量系统自标定技术研究

Indoor GPS工业测量系统在进行测量前必须标定各发射头之间的相对位置关系及其空间姿态,针对此自标定问题,采用单个圆柱型传感器配合标准尺进行测量,获得空间点相对于各发射头中心的水平方位角和垂直方位角,在此基础上建立了基于角度值的坐标参数转换模型,采用非线性最小二乘法进行解算以完成Indoor GPS的自标定。实验证明该方法简便可行。     

温升试验中温升测量结果的不确定度评定

本文对低压成套开关设备温升试验的测量方法、测量系统和测量程序等方面进行了分析,识别出检测结果的测量不确定度来源,并对温升试验中某点温升测量值的不确定度进行了评估。     

大气环境温度与压力传感器的自动化标定系统研究

目前大气环境传感器的测试和标定主要依赖于人工手动操作完成,测试和标定效率较低,结果准确率较差。为解决该问题,在分析大气环境传感器工作原理的基础上,搭建了一套由真空泵电机、气压控制器、高低温箱、金属密封腔、标准数字温度计、工控机、待标定大气环境传感器等部分组成的大气环境传感器硬件测试平台,并设计了大气环境自动化软件测试系统,通过工控机控制标准环境,对标准环境参数进行周期采样,自动判定稳态并记录标定所需参数,从而拟合出标定曲线。对待标定温度和压力传感器进行自动化标定测试,结果显示：温度标定的拟合相关系数为0.994 5,重复性误差为0.087%;压力标定的拟合相关系数为0.996,重复性误差为0.046%,验证了测试系统的可行性。此研究成果为大气环境传感器快速部署应用提供了有力支撑,对于推动自动化技术在大气环境参数测量领域中的应用具有重要意义。     

热电偶温度自动测量及预测系统研制

在利用热电偶对石油、石化等场所的设备进行温度测量时,由于某些测试环境的特殊性,这就要求热电偶对测温点进行"瞬态"测量,而热电偶的热接点由于受热惯性的影响,短时间很难对测温点进行准确测量.考虑到热电偶测温的阶跃响应特性,利用计算机及A/D转换装置研制了热电偶温度自动监测系统并编制了温度测试系统"预测"软件,在对部分采样的数据进行线性回归后,可实现对温度信号的自动采集及对测量值的跟踪"预测",缩短了测试时间并降低了测试强度.     

一种基于MATLAB的植物叶片参数测量系统

提出了一种基于MATLAB的植物叶片参数自动测量系统方案.该系统利用扫描仪获取包含标定物的叶片图像,对其二值化后进行边缘跟踪,获得标定物和叶片的边界,最后借助标定物的实际直径和面积得到叶片的面积、周长、长、宽等参数.经对两种叶片进行的实验.结果表明,此系统能够快速、准确地进行叶片参数的自动测量,具有较高的效率和实用性.     

标准太阳电池标定值计量方法研究

基于差分光谱响应度法搭建了标准太阳电池标定值校准装置,分析了标准太阳电池绝对光谱响应度随电池温度和偏置光辐照度的变化关系,通过数值拟合得到太阳电池短路电流与偏置电流的关系,实现太阳电池标定值测量不确定度1.2%(k=2)。搭建了标准太阳电池标定值户外计量装置,实现测量不确定度2.38%(k=2)。差分光谱响应度法与户外总辐射法测量结果比对的比率值为0.95,表明2种方法测量结果在不确定范围内量值等效。     

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.     

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.     

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.     

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)。