自镇流LED灯光效测量不确定度评定

通过测量自镇流LED灯的光通量和功率,计算得到光效,建立了不确定度评定的数学模型,分析了测量过程中存在的不确定度来源,量化了不确定度分量,从而求出了合成不确定度和扩展不确定度。     

LED 2π空间光通量测量方法及不确定度分析

光通量是LED最重要的参数之一,在LED光通量测量中通常使用积分球对其进行标定。由于LED与传统光源相比在自身结构和发光特性上有很大的不同,特别是在LED 2π空间光通量测量中,其自吸收效应以及积分球内挡屏都有可能带来测量误差,分析中通过实验对影响LED光通量测量的主要因素进行对比,并予以讨论。同时,通过选择适当的实验对象和装置,以及测量过程中对各影响因素的计算,分析LED 2π空间总光通量的测量不确定度。     

发光二极管(LED)国家光度标准的研究

用变角光度测量装置建立LED光度标准的方法,LED光强度测量不确定度为3.9%,LED光通量测量不确定度为4.8%.     

测量不确定度的分析及应用

本文对测量误差和测量不确定度的基本概念作了简单介绍,得出测量结果的可靠程度是通过分析和评定测量不确定度来确定的;本文着重介绍和探讨了测量不确定度的计算步骤和计算方法,并结合电气实验室经常遇到的电压测量给出不确定度分析和计算实例;本文还介绍了单次测量条件下如何利用已知条件进行不确定度的估计以及不确定度的应用范围。     

发光二极管（LED）国家光度标准的研究

用变角光度测量装置建立LED光度标准的方法，LED光强度测量不确定度为3．9％，LED光能量测量不确定度为4．8％。     

产品质量检测不确定度的分析及应用

本文对测量误差和测量不确定度的基本概念作了简单介绍，得出测量结果的可靠程度是通过分析和评定测量不确定度来确定的；本文着重介绍和探讨了测量不确定度的计算步骤和计算方法，并结合电气实验室经常遇到的电压测量给出不确定度分析和计算实例；本文还介绍了单次测量条件下如何利用已知条件进行不确定度的估计以及不确定度的应用范围。     

变压器油含水量测量结果不确定度评定

本文对电力变压器油含水量测量不确定度进行评定,建立了数学模型,通过对影响测量结果的不确定度分量的分析,计算出被测量的合成不确定度和扩展不确定度。     

变压器电压比测量结果的不确定度评定

本文介绍了电力变压器的电压比测量不确定度的评定。建立了数学模型,通过对影响测量结果的不确定度分量的分析和量化计算被测量的合成不确定度和扩展不确定度。     

影像测量仪尺寸测量误差不确定度评定

该文运用GUM方法,建立测量模型,对影像测量仪尺寸测量误差进行测量不确定度评定,并分析其不确定度分量的各个来源,其中包括标准器引入的不确定度分量、环境因素引入的不确定度分量及测量重复性引入的不确定度分量。通过一系列计算,最终得到各校准点的测量结果不确定度,为广大测量人员提供不确定度分析参考依据;便于在实际测量中通过查表调用或带入公式计算直接得到不确定度,提高工作效率;为下一级测量引入一条不间断的测量链,保证量值的准确可靠。     

变压器油击穿电压测量结果不确定度评定

本文对变压器油击穿电压测量不确定度进行评定,建立了数学模型,通过对影响测量结果不确定度分量的分析,计算出被测量的合成不确定度和扩展不确定度。     

第四代光谱辐射度和色温度国家基准装置的研制

基于高温黑体辐射源BB3500M研究并建立了第四代光谱辐射度和色温度国家基准装置。采用稳流和稳温相结合的反馈工作模式,开启后3 h即达到温度稳定。3 016 K时,1 h内的温度变化小于0.59 K。温度测量直接溯源至Pt-C和Re-C高温共晶点黑体,2 980 K时的测量不确定度为0.64 K(k=1)。光谱辐射亮度和光谱辐射照度的波长范围向短波分别扩展至220 nm、230 nm,长波扩展至2 550 nm,达到全波段光谱辐射亮度CCPR-S1比对的能力。新基准增加了分布温度参数的测量能力,2 353 K和2 856 K的测量不确定度(k=1)分别改善为1.6 K和2.1 K。对基准装置入射光学系统的辐照不均匀性以及短波紫外大气传输过程所带来的散射和吸收进行了数值计算,提出理论修正方法,将辐照不均匀性测量误差减小0.3%,大气传输误差减小0.29%。     

Spectral Radiation Drift of LEDs Under Step-Mode Operation and Its Effect on the Measurement of the Non-Linearity of Radiation Thermometers

The non-linearity (NL) of radiation thermometers is critically involved when realizing ITS-90 above the silver point. It has to be corrected for, and its uncertainty should be adequately specified. In this article, results are presented of NL measurements based upon the superposition method and involving light emitting diodes (LEDs) with high radiance output, peaked at a wavelength of 645 nm. To this end, the two LEDs in question have been operated in the pulse mode with a fixed phase shift. Their spectral radiances have been measured by the radiation thermometers to be tested, separately or superimposed by means of a beam splitter. Still the drift in the spectral radiance observed after switching on the LEDs has to be taken into account and corrected for, since this drift, interfering during the superposition procedure, could corrupt the sum rule for the fluxes involved, which is the crux of the superposition method. Therefore, experimental research has been carried out to characterize the drift of LEDs operated in the pulse mode with a fixed phase shift. The result indicated that the drift could be roughly specified in terms of characteristic time intervals: non-linear drift in the first tens of seconds followed by a quasi-linear drift in the subsequent time interval. The crossover time from non-linear to quasi-linear drift could be ascertained by experiment. In the course of the superposition process, switching of the LEDs was done in such a way that only the quasi-linear part of the drift was involved which allowed for the correction of the drift in the NL measurements, as will be reported. Two radiation thermometers were involved in the NL measurements at radiance temperatures between the silver point and 3153 K: an LP-4, with a central wavelength of 650 nm and 10 nm bandwidth, manufactured by KE-Technologie and the primary standard pyrometer PSP, with a central wavelength of 660 nm and 10 nm bandwidth, developed by NIM.     

Thermodynamic Radiation Thermometry Using Radiometers Calibrated for Radiance Responsivity

Using radiometry, thermodynamic temperatures can be determined by a variety of experimental techniques. Radiometers without imaging optics can be calibrated for spectral power or spectral irradiance responsivity, and radiometers with imaging optics can be calibrated for radiance responsivity. These separate approaches can have different uncertainty components with different uncertainty values. At NIST, thermodynamic radiation thermometry is performed using radiation thermometers calibrated for radiance responsivity using laser-irradiated integrating sphere sources (ISS). The radiance of the ISS is determined using Si-trap detectors whose spectral power responsivity is traceable to the electrical substitution cryogenic radiometer. The radiometric basis of the NIST approach is discussed. The uncertainty budget for the measurements as well as the characterizations to determine the component uncertainty values is listed.     

网络时间同步的不确定度评定研究

为了评定网络时间同步的不确定度,基于中国计量科学研究院的网络时间服务系统,以时间综合测量仪 TimeAcc-007为时差测量仪器,在局域网环境下设计并进行网络时间同步实验。分析了客户端和服务器端同步实验测量的时差数据,建立了网络时间同步的时差不确定度数学模型,分析并评定了测量结果重复性、服务器参考 源、服务器时间戳、客户端时间戳及网络往返路径时延等不确定度分量。结合不确定度分析结果,提出了改善网络 授时精度的相关算法。     

Applicability of light-emitting diodes as light sources for active differential optical absorption spectroscopy measurements

We present what is to our knowledge the first use of light-emitting diodes (LEDs) as light sources for long-path differential optical absorption spectroscopy (LP-DOAS) measurements of trace gases in the open atmosphere. Modern LEDs represent a potentially advantageous alternative to thermal light sources, in particular to xenon arc lamps, which are the most common active DOAS light sources. The radiative properties of a variety of LEDs were characterized, and parameters such as spectral shape, spectral range, spectral stability, and ways in which they can be influenced by environmental factors were analyzed. The spectra of several LEDs were found to contain Fabry-Perot etalon-induced spectral structures that interfered with the DOAS evaluation, in particular when a constant temperature was not maintained. It was shown that LEDs can be used successfully as light sources in active DOAS experiments that measure NO2 and NO3 near 450 and 630 nm, respectively. Average detection limits of 0.3 parts in 10(9) and 16 parts in 10(12) respectively, were obtained by use of a 6 km light path in the open atmosphere.     

光谱辐射亮度国际比对与结果分析

基于高温黑体辐射源BB3500M,中国计量科学研究院(NIM)自主研制了第四代光谱辐射亮度国家基准装置,波长范围覆盖220~2550nm,以稳定的钨带灯作为传递标准,改善了测量不确定度。黑体辐射源的温度测量溯源至Pt-C和Re-C固定点黑体,在3021 K采用WC-C固定点黑体进行验证,NIM和全俄光学物理计量院(VNIIOFI)之间的测量偏差小于70 mK。采用新基准装置,NIM参加了光谱辐射亮度国际APMP-PR.S6比对。NIM研制了两套入射光学系统,成像倍率分别为0.58和1.00,立体角为0.006sr和0.008sr,采用两套系统复现光谱辐射亮度量值的差异小于±0.40%。APMP-PR.S6比对结果表明:在紫外、可见和近红外波长范围,NIM与参考值的平均相对偏差分别为0.59%、0.44%和0.34%。全部波长范围的平均相对偏差0.46%。在250nm、400nm、800nm、2500nm波长,光谱辐射亮度的测量标准不确定度分别为0.95%、0.50%、0.41%和0.80%。从而验证了第四代光谱辐射亮度国家基准装置的准确性和可靠性。     

高精密自动绝热量热计

介绍了中国计量科学研究院用新近开发的高精密自动绝热量热计的测量控制系统对美国国家标准技术研究院（NIST）的标准物质α-Al2O3进行的比热测量,并对测量结果和不确定度作了分析。该自动绝热量热计是中国计量科学研究院原有的绝热量热计的发展,它继承了原有量热计的本体,又开发了高精度量热和温度自动测量控制系统。进行了与NIST的数据和其它数据对比以及不确定度分析。测量结果与NIST的数据相比,其相对均方根偏差为0．447％,一致性为0．167％。合成相对标准不确定度为0．333％。结果表明,该自动绝热量热计具有高精密量热和比热测量的能力。     

Development of a Tunable LED-Based Colorimetric Source

A novel, spectrally tunable light-source utilizing light emitting diodes (LEDs) for radiometric, photometric, and colorimetric applications is described. The tunable source can simulate standard sources and can be used as a transfer source to propagate photometric and colorimetric scales from calibrated reference instruments to test artifacts with minimal increase in uncertainty. In this prototype source, 40 LEDs with 10 different spectral distributions were mounted onto an integrating sphere. A voltage-to-current control circuit was designed and implemented, enabling independent control of the current sent to each set of four LEDs. The LEDs have been characterized for stability and dependence on drive current. The prototype source demonstrates the feasibility of development of a spectrally tunable LED source using LEDs with up to 40 different spectral distributions. Simulations demonstrate that such a source would be able to approximate standard light-source distributions over the visible spectral range—from 380 nm to 780 nm—with deviations on the order of 2 %. The tunable LED source can also simulate spectral distributions of special sources such as discharge lamps and display monitors. With this tunable source, a test instrument can be rapidly calibrated against a variety of different source distributions tailored to the anticipated uses of the artifact. Target uncertainties for the calibration of test artifacts are less than 2 % in luminance and 0.002 in chromaticity for any source distribution.     

An Optical Frequency Comb Tied to GPS for Laser Frequency/Wavelength Calibration

Optical frequency combs can be employed over a broad spectral range to calibrate laser frequency or vacuum wavelength. This article describes procedures and techniques utilized in the Precision Engineering Division of NIST (National Institute of Standards and Technology) for comb-based calibration of laser wavelength, including a discussion of ancillary measurements such as determining the mode order. The underlying purpose of these calibrations is to provide traceable standards in support of length measurement. The relative uncertainty needed to fulfill this goal is typically 10⁻⁸ and never below 10⁻¹², very modest requirements compared to the capabilities of comb-based frequency metrology. In this accuracy range the Global Positioning System (GPS) serves as an excellent frequency reference that can provide the traceable underpinning of the measurement. This article describes techniques that can be used to completely characterize measurement errors in a GPS-based comb system and thus achieve full confidence in measurement results.