共查询到18条相似文献,搜索用时 875 毫秒
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直流电流比差仪(外形见本期广告插页)用来测量两直流电流的比差。当把分流器上通过的被测电流及分流器电阻上的压降变换成电流并通入比差仪,则比差仪的示值直接反映出分流器电阻值的相对误差。此测量方法比分流器阻值的双电桥测量法、电位差计测量法要准确、方便得多,并适合于现场检定。 相似文献
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综合相对测量法能克服绝对测量法的不足,有效提高介质损耗角的在线测量精度,目前研究仅限于2到3台同相电容型设备的综合相对测量法的应用,不具普遍性。本文介绍了综合相对测量法的基本原理,以3台和4台同相设备的综合相对测量法的应用为例,利用归纳方法,给出N(N≥3)台设备中任意i(1≤i≤N)台设备的故障诊断矩阵,为综合相对测量法的使用提供了依据。根据阈值诊断和模糊数学理论,提出了基于综合相对测量法的两种故障诊断方法及影响其正确诊断的几个因素,为综合相对测量法的实际使用提供了思路。 相似文献
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1000kV CVT误差的现场试验方法 总被引:4,自引:1,他引:3
1000kV电容式电压互感器(CVT)是我国特高压交流试验示范工程中的新型设备,其准确度(误差)的现场试验在世界上没有先例。为确保1000kV CVT误差现场试验的顺利实施,开展了对1000kV CVT现场试验方法的研究,结合试验示范工程用1000kV CVT的结构特点和具体参数,提出了差值法、电压系数测量法等3种方法,通过比较这些方法的优缺点,表明在现场宜用1000kV电磁式标准电压互感器作为试验标准、采用差值法进行CVT的准确度(误差)现场试验;根据试验方法所需的标准装置,研制出1600kV标准电容器、1000kV量值传递用和现场用电磁式标准电压互感器。同时,对测量中可能导致不确定度的来源进行分析,使测量中的偏差控制在允许误差的1/3以内。 相似文献
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计量保证方案(MAP)是目前国际上通用的确保量值传递体系完整的技术措施之一。电能计量保证方案(EMAP)是计量保证方案(MAP)在电能量值传递体系中的具体应用,其核心技术是通过定期的期间核查和量值比对收集数据,采用概率论(probability)和数理统计(statistics)的理论和方法,建立相应的数学模型,并对核查和比对的测量数据进行分析评估,再根据评估结果判断计量检定机构的检测能力及水平,提出影响计量检定机构检测水平的主要因素,并给出纠正方案。电能计量保证方案在量值传递过程中起到承上起下的作用,以保证系统量值传递的准确、可靠和统一,并作为申请计量授权工作的重要技术依据。 相似文献
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本文叙述国际电报电话谘询委员会(CCITT)和国际无线电谘询委员会(CCIR)所推荐的测量群时延特性的双载频交替测量法。文中讨论了普通Nyquist方法测量群时延特性所遇到的困难,分析了采用双载频交替测量法的优点,对该方法的原理作了通俗的说明。 相似文献
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本文介绍了中国计量科学研究院发展的光学密度,光谱规则透射比,漫反射比,漫反射因数等光谱光度计量基准标准的测量原理,基本结构和测量不确定度,以及相应的一系列计量标准物质的性能。 相似文献
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一、常用维修方法液晶(LCD)彩电电源板的维修方法与CTR(显像管)彩电电源电路的维修方法基本相同。除了采用常见的"直观检查法"、"电阻测量法"、"电压测量法"、"波形测量法"等方法外,根据液晶彩电电源板的电路结构和特点,还可采用以下几种方法。1.外接电压法"外接电压法"就是将机外或机内适合需求的电压或信号,接入电源板相应的位置,为相关电路供电,根 相似文献
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de Vries G. Beek J.F. Lucassen G.W. van Gemert M.J.C. 《IEEE journal of selected topics in quantum electronics》1999,5(4):944-947
The double integrating sphere setup (DIS) measures diffuse reflectance, diffuse transmittance and collimated transmittance, from which the optical properties of tissue (the absorption coefficient μ a, the scattering coefficient μs and the anisotropy of scattering g) are estimated. The effect of light losses in the DIS and optical thickness on optical properties estimation by the inverse adding doubling algorithm (IAD) and uniqueness of measurement have been investigated using a Monte Carlo method. Results were obtained for optical properties in turbid tissues (0.80⩽albedo⩽0.99, 0.80⩽anisotropy⩽ 0.99, 1.5⩽optical thickness⩽7.5) sandwiched between glass slides. At optical thickness=6.0 the loss of light through the glass slides is ranging from 13%±0.5% (at albedo=0.80) to 15%±0.5% (at albedo=0.98) of the incident power. The loss of light at the exit port in the transmittance sphere is increasing up to 50% of the incident power at highly forward scattering. These losses result in a dependency on optical thickness of the optical properties estimation by the IAD algorithm. Furthermore, because of these losses, the DIS setup measurement is found to be fundamentally nonunique, when simultaneously measuring the diffuse reflectance, diffuse transmittance and collimated transmittance 相似文献
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Jackson A.W. Pinsukanjana P.R. Gossard A.C. Coldren L.A. 《IEEE journal of selected topics in quantum electronics》1997,3(3):836-844
Improved control over layer thickness has been realized using optical interference techniques such as reflectance spectroscopy. It is now common to observe spectra of distributed-Bragg-reflector (DBR) mirrors during growth to make corrections for growth rate drifts. Real-time optical flux monitoring (OFM) by atomic absorption allows precise layer control by measuring group III fluxes continuously during growth. The flux information can be used to operate growth shutters and to control effusion cell heaters in a feedback loop. Improved substrate temperature measurement by diffuse reflectance spectroscopy (DRS) allows precise measurement of substrate temperature. DRS is not subject to the same errors encountered in pyrometer or thermocouple measurements of substrate temperature 相似文献
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在日常使用积分球对测试样品进行光通量测量的时候会发现即使是同一套测试设备和同一个测试样品在相隔几个月后重新进行光通量测量有一定概率会得到有一定差异的结果。而造成这个差异的原因则有可能是试验时积分球内温度不同而导致的。我们通过多款不同类型的灯具分别在多个不同积分球球内温度下进行试验,并对试验结果展开分析,最终发现:不同温度下光通量测量不同,是由于灯具在不同温度下发出光通量不同所导致的。 相似文献
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Wei-Chiang Lin Toms S.A. Jansen E.D. Mahadevan-Jansen A. 《IEEE journal of selected topics in quantum electronics》2001,7(6):996-1003
A simple but effective method of spectral processing was developed to minimize or remove the effects of the presence of superficial blood on tissue optical spectra and, hence, enhance the performance of optical-spectroscopic-based in vivo tissue diagnosis and surgical guidance. This spectral-processing algorithm was developed using the principles of absorption-induced light attenuation wherein the ratio of fluorescence intensity (F) and the hth power of diffuse reflectance intensity (Rd) at a given emission wavelength λm is immune to spectral distortions induced by the presence of blood on the tissue surface. Here, the exponent h is determined by the absorption coefficients of whole blood at the excitation and emission wavelengths. The theoretical basis of this spectral processing was verified using simulations and was experimentally validated. Furthermore, the optical spectra of brain tissues collected in vivo was processed using this algorithm to evaluate its impact on brain tissue differentiation using combined fluorescence and diffuse reflectance spectroscopy. Based on the simulation, as well as experimental results, it was observed that using F/Rdh h can effectively reduce or remove spectral distortions induced by superficial blood contamination on tissue optical spectra. Thus, optical spectroscopy can also be used intraoperatively for applications such as surgical guidance of tumor resection 相似文献
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