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1.
Most platinum resistance thermometers (PRTs) sent to CENAM for calibration are of the industrial type (IPRT). The cells used
to calibrate both standard PRTs (SPRTs) and IPRTs form part of the national standard of temperature. In order to reduce their
use, we built a set of fixed-point cells, furnaces, and baths to calibrate IPRTs using fixed points, including an apparatus
and cells to reproduce the Hg triple point. To realize the triple point of mercury (TP-Hg), an apparatus that operates from
room temperature to − 45 ◦C using a CENAM-constructed heat pipe was designed and built. With the heat pipe, it is unnecessary to use a recirculation
bath to provide a temperature-controlled environment, the temperature gradient is reduced, and the system is more efficient
because its thermal mass is reduced. In this way, it is possible to reproduce the TP-Hg for long periods of time to facilitate
IPRT calibration, using cells of smaller size than is conventional and without using expensive liquid baths. The system was
tested with cells having 400 g and 800 g of mercury, and a reproducibility of about 0.1 mK was obtained. 相似文献
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本文介绍了长度在44mm-109mm,直径不大于8mm的各种型号热电偶在锑凝固点(660,323℃)上的一种分度方法。 相似文献
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按时规范,JJF1059-1999,对二等标准铂电阻温度计在锌凝固点及水沸点检定的不确定度进行了评定,通过建立测量数学模型确定各标准各不确定度分量,并按不确定度传播公式给出固定点间各温度点的扩展不确定度及包含因子。 相似文献
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本文介绍了在检定83.8058K~273.16K温度范围铂电阻温度计时,用液氮点代替氩三相点的有关装置、检定方法和检定结果处理,以及用液氮点与用氩三相点检定结果的比较。 相似文献
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K. Anhalt A. Zelenjuk D. R. Taubert T. Keawprasert J. Hartmann 《International Journal of Thermophysics》2009,30(1):192-202
The paper describes the new experimental setup assembled at the PTB for the absolute spectral responsivity measurement of
radiation thermometers. The concept of this setup is to measure the relative spectral responsivity of the radiation thermometer
using the conventional monochromator-based spectral comparator facility also used for the calibration of filter radiometers.
The absolute spectral responsivity is subsequently measured at one wavelength, supplied by the radiation of a diode laser,
using the new setup. The radiation of the diode laser is guided with an optical fiber into an integrating sphere source that
is equipped with an aperture of absolutely known area. The spectral radiance of this integrating sphere source is determined
via the spectral irradiance measured by a trap detector with an absolutely calibrated spectral responsivity traceable to the
primary detector standard of the PTB, the cryogenic radiometer. First results of the spectral responsivity calibration of
the radiation thermometer LP3 are presented, and a provisional uncertainty budget of the absolute spectral responsivity is
given. 相似文献
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针对混合制冷剂等挥发性混合物粘度测量的需要,研制了一种新的适用于测量低沸点混合物粘度的旋转式毛细管粘度计。该新型粘度测量装置在压力容器内嵌入旋转式毛细管粘度计,将旋转法升液和压力容器承压结合起来,避免了传统密封型毛细管粘度计由于抽放气的升液方式而导致混合物成分的变化,可以实现在较高压力下循环测量挥发性混合物溶液的粘度。采用R22和R290对旋转式毛细管粘度计进行了标定,并用R410A对粘度计的测量精度和性能进行了评价,粘度测量值与文献值最大相对偏差为0.81%。 相似文献
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氩三相点作为国际温标ITS-90的重要低温固定点,在国家基准量值传递中有着重要的意义。中国计量科学研究院研制了基于准绝热原理的密封型氩三相点装置,能够对长杆铂电阻温度计进行氩三相点高精度复现,并且通过开发自动控制与测量软件实现了实验过程自动化测量与控制。实验结果表明,使用新研制的密封氩三相点装置使氩三相点的温坪时间提高到23 h以上,其中在16 h的温坪变化在0.2 mK以内,同时温坪复现性达到0.1 mK以内,成功解决了恒定热流法氩三相点复现过程中温坪时间短、复现难度大等问题,保证国家基准量值传递的准确性。 相似文献
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介绍了真空绝热法测量材料低温比热的原理及方法。考虑到测量系统中样品架、加热器及温度计等附加物引入的热容因素,建立了比热测量误差的传递关系式,并给出了分析数据。对具体测量中有关精度的问题进行了探讨。 相似文献
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If a radiation thermometer is calibrated by measuring the temperatures of two cavities having different geometries, sometimes
discrepancies arise between them, even though their emissivities are close to that of a blackbody. The origin of such discrepancies
may result from the size-of-source effect, and in the distance-to-target effect for those thermometers that offer focusing
capability. Examples include: (a) out-of-focus image changes the reading: different focus settings produce different results
and (b) measurements taken at different distances produce different results. These effects are discussed, their contribution
to the measurement uncertainty is evaluated, and some recommendations are made for practical blackbody cavities or radiators
to reduce such effects. 相似文献
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A. Onuki 《International Journal of Thermophysics》1998,19(2):471-479
Nucleation near the gas–liquid critical point depends sensitively on whether the pressure or the volume is fixed. We consider near-critical fluids close to the coexistence curve. (i) Upon decompression to a constant pressure with a fixed boundary temperature, bulk nucleation can well be induced from a gas state, whereas from a liquid state boiling is easily triggered in the thermal diffusion layer near the boundary. In this case, bulk nucleation in a metastable gas is described by the classical Lifshitz–Slyozov theory. (ii) Upon cooling of the boundary temperature under the fixed-volume condition, bulk nucleation can be realized in a liquid and a modified Lifshitz–Slyozov theory follows. However, if a gas is cooled from the boundary at a fixed volume, liquid droplets readily appear in the thermal diffusion layer, apparently suggesting no metastability in a gas in agreement with previous experiments. (iii) On the other hand, if a liquid is heated at the boundary wall, boiling readily occurs both at a fixed volume and at a fixed pressure. 相似文献
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首先介绍了系统误差的定义及分类,包括定值系统误差和变值系统误差,其中变值系统误差又分为线性系统误差和周期系统误差;然后分别介绍了不同种类的系统误差对测量结果的影响以及发现方法,最后阐述了消除和减少各种系统误差的方法。 相似文献
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在液氮自然循环流动时,对竖直多孔表面管管内沸腾换热及外管单面加热时竖直多孔表面套管内沸腾换热,进行了实验研究,分析并讨论了通道的当量半径、热流密度及含气率对沸腾换热的影响。 相似文献
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Nadine Kosseifi Pascal Henry Biwole Christian Mathis Germain Rousseaux Sverine Agnes Eliette Boyer Harunon Nakagawa Yoshlkaw Thierry Coupez 《材料科学与工程:中英文B版...》2013,(5):281-290
The laser-induced fluorescence (LIF) thermometry is applied to measure the temperature field surrounding a single vapor bubble growing at an artificial nucleation site. In order to correct measurement errors due to the non-uniformity of the incident laser intensity, the two-color LIF thermometry technique is used in this nucleate boiling experiment. This technique is based on the use of two fluorescent dyes: the temperature sensitive dye Rhodamine B and the temperature insensitive dye Sulforhodamine-lO1. The concentration of the dyes is optimized by analyzing the behavior of fluorescence intensities. The mapping between the two images is determined through a geometrical calibration procedure. This technique presents a success in correcting the non uniformities due to the reflection of the light at the bubble surface and to the temperature gradient. The obtained temperature fields show that the two-color LIF is a promising technique in the investigation of nucleate boiling. 相似文献
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A. Silva Ribeiro J. Alves e Sousa C. Oliveira Costa M. Pimenta Castro M. G. Cox 《International Journal of Thermophysics》2008,29(3):902-914
The uncertainty required by laboratories and industry for temperature measurements based on the practical use of platinum
resistance thermometers (PRTs) can commonly be achieved by calibration using temperature reference conditions and comparison
methodologies (TCM) instead of the more accurate primary fixed-point (ITS-90) method. TCM is suitable for establishing internal
traceability chains, such as connecting reference standards to transfer and working standards. The data resulting from the
calibration method can be treated in a similar way to that prescribed for the ITS-90 interpolation procedure, to determine
the calibration coefficients. When applying this approach, two major tasks are performed: (i) the evaluation of the uncertainty
associated with the estimate of temperature (a requirement shared by the ITS-90 method), based on knowledge of the uncertainties
associated with the temperature fixed points and the measured electrical resistances, and (ii) the validation of this practical
comparison considering that the reference data are obtained using the ITS-90 method. The conventional approach, using the
GUM uncertainty framework, requires approximations with unavoidable loss of accuracy and might not provide adequate uncertainty
evaluation for the methods mentioned, because the conditions for its valid use, such as the near-linearity of the mathematical
model relating temperature to electrical resistance, and the near-normality of the measurand (temperature), might not apply.
Moreover, there can be some difficulty in applying the GUM uncertainty framework relating to the formation of sensitivity
coefficients through partial derivatives for a model that, as here, is somewhat complicated and not readily expressible in
an explicit form. Alternatively, uncertainty evaluation can be carried out by a Monte Carlo method (MCM), a numerical implementation
of the propagation of distributions that is free from such conditions and straightforward to apply. In this paper, (a) the
use of MCM to evaluate uncertainties relating to the ITS-90 interpolation procedure, and (b) a validation procedure to perform
in-house calibration of PRTs by comparison are discussed. An example illustrating (a) and (b) is presented. 相似文献
20.
Results of an investigation of small-size ampoules of the fixed points of gallium and indium are described. It is concluded that they can be used as an inexpensive standard means of measuring temperature. 相似文献