共查询到20条相似文献,搜索用时 15 毫秒
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《IEEE transactions on instrumentation and measurement》1972,21(4):350-353
The principle of power measurement by thermal means has the advantage of a very large bandwidth and gives the possibility to realize time or frequency encoding in a simple way. The new method described is based on a known operation using special thermal converters with several heaters. The multiple heating, however, is done by a multiplexing operation on single-heater converters. It is shown that, by means of this principle, a power meter can be set up enabling precision measurement in a wide range of frequency. The measurement of real power in polyphase systems is another application of the same principle. 相似文献
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工频接地电阻测量是电气测量的基本参数之一,但在实际测量存在许多问题,导致测量结果不准确,文章以最常用的三极直线法测量工频接地电阻为例,结合国家有关规范和标准的要求,对接地装置的接地电阻测量原理进行分析和总结,提出提高测量结果准确性的意见和建议。 相似文献
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《IEEE transactions on instrumentation and measurement》1972,21(3):255-258
A direct digital method of measuring the noise power in a low-pass random waveform is described. The input-output relationship and the sensitivity of the digital detector are determined. Direct digital measurement of noise power offers a number of advantages in the instrumentation of radiometers and other noise-measuring systems. 相似文献
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频率测量结果的不确定度是频率测量系统测量质量的重要指标,按照不确定的A类和B类分量的评定方法,本文分析了用频标比对法对高精度频率源进行测量时各种因素影响引入的不确定度,并提出了该方法测频的不确定度评定公式,同时又给出了频率源老化率指标的不确定度评定方法.实验表明,本文的不确定度分析方法是正确和有效的. 相似文献
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介绍了针对低频噪声源三种参数的测试方法.讨论了低频噪声源的最大输出功率、噪声输出幅度以及噪声带宽测试的实现途径. 相似文献
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基于混沌理论的频率测量方法 总被引:5,自引:0,他引:5
本文提出了应用混沌理论来进行频率测量的新方法。基于混沌系统对初值以及参数极度敏感的特性,将使频率的测量过程具有较高的精确度和灵敏度。理论分析和仿真结果都证明了这种方法的有效性。 相似文献
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介绍一种简便测定材料硬度与弹性模量比(H/E)的新方法,根据维氏硬度压痕的加载和卸载曲线的差别就可直接计算 H/E 值。 相似文献
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拟合测量正弦信号频率的不确定度 总被引:1,自引:0,他引:1
介绍了用四参数最小二乘曲线拟合法评价正弦信号频率时不确定度的分析和评价.通过使用国军标GJB 3756-1999"测量不确定度的表述及评定"中推荐的方法,讨论了影响评价结果不确定度的几个主要误差来源,包括采集速率误差、采集序列的谐波失真、采集序列的噪声及非谐波失真、采集序列中信号周期的抖动、软件拟合运算误差的影响等,给出了正弦信号频率的测量不确定度及减小不确定度的主要措施.结合一个实际例证的评价结果,验证了该过程的正确性和可行性. 相似文献
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《Journal of Modern Optics》2013,60(7):813-821
The laser speckle pattern produced by the coherent illumination of a small circular portion of a doubly exposed photograph contains enough information to reveal not only the displacement but also the rotation of a rigidly moving two-dimensional field. The displacement of the field is contained in the resulting parallel speckle fringe spacing in the usual way. The magnitude of the rotation of the field, however, may be determined by measuring the radius of the circular region within which these displacement speckle fringes appear. Photographs and analyses of the resulting speckle patterns are presented. Non-rigid two-dimensional motion and its relation to incompressible fluid flow is also discussed. 相似文献
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针对变压器工频短路电流测量需求,研究了外积分式罗氏线圈技术和光纤电流传感技术。建立了2种传感器的低频数学模型,基于MATLAB/Simulink仿真计算传感器对工频短路电流的响应特性,结果表明:罗氏线圈对工频短路电流的测量精度受其下截止频率影响,下截止频率越低,测量精度越高;光纤电流传感器理论上可以精确复现工频短路电流。采用多种电流传感器进行变压器工频短路电流现场对比测试,结果表明:电流比较仪、光纤电流传感器及下截止频率为0.02Hz的罗氏线圈测得的电流波形吻合较好,而下截止频率为0.2Hz的罗氏线圈测量结果出现了明显的偏移,且无法归零,与仿真分析结论基本一致。对于外积分式罗氏线圈,为保证高精度测量,建议下截止频率应低于0.1Hz;光纤电流传感器具有极好的直流及低频响应特性,是工频短路电流高精度测量的理想方案。 相似文献
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为了解决测量噪声下的损伤定位和定量识别问题,提出了基于测量位移的两阶段识别方法和基于统计理论的损伤敏感度分析方法。首先利用损伤刚度的改变特性和测量位移来确定损伤指标,再通过损伤指标的相关自由度变化来确定损伤单元,然后利用自由度缩聚的方法推导出损伤程度的定量计算公式。并利用统计理论来分析噪声对识别结果的影响,推导出损伤指标和损伤程度的噪声敏感性计算公式。数值仿真结果表明,基于测量位移的两阶段损伤识别方法不仅可以精确的识别出损伤位置和程度,而且识别效果受测量噪声的影响较小,该方法明显优于直接广义逆法。 相似文献
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《IEEE transactions on instrumentation and measurement》1983,32(4):508-509
An advanced temperature control system has been developed for calorimetric method of electromagnetic wave power measurement. The temperature deviation can be reduced by repeatedly substituting the controlled variable through a DA converter and an adder. The system has been applied to a calorimeter for laser power with experimental results yielding good agreement with analytical predictions. 相似文献
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《IEEE transactions on instrumentation and measurement》1972,21(4):353-357
The accuracy and frequency response limitations in the present square-law responding laboratory wattmeters have promoted the search for alternate methods of ac power measurement using electronic instrumentation. The three-voltmeter method is based on an old principle of operation implemented by new analog circuitry. Results of the tests reported here show a precision of power calculation with 0.01 percent error at frequencies below 5 kHz. A unique test procedure is described for the comparison of the three-voltmeter device and a time-division multiplier wattmeter operating at zero power factor. 相似文献