高精度钠热管固定点炉及其等温特性

介绍了中国计量科学研究院新研制的两台高精度钠热管固定点炉(SHPF-1、SHPF-2),并测量了其垂直温场.当这两台钠热管固定点炉的炉温分别控制在比铝凝固点低约2℃、3℃时,铝点容器温度计阱底部150 mm范围内温场均匀性分别为15 mK和11 mK,并与国外同类的钠热管固定点炉的技术指标进行比较.此外,分析了影响固定点炉等温性能的因素.     

高精度钾热管铝凝固点炉研制及性能测试

热管作为等温炉衬可提高固定点炉温场均匀性。为提高铝凝固点复现水平,研制了1套高精度钾热管铝凝固点炉。介绍了钾热管和固定点炉的研制流程,并测试了钾热管固定点炉性能。测试结果表明:采用分段升温的方式,炉子升温曲线平缓,整个升温过程中没有明显过冲现象,可有效保护铝凝固点容器的使用寿命;钾热管铝凝固点炉垂直温场均匀性为6.6mK;利用该钾热管铝凝定点炉可以实现铝凝固点温坪的复现,温坪重复性为0.02mK。     

三段控温固定点炉复现铝凝固点研究

固定点炉垂直温场均匀性是影响ITS-90国际温标固定点温坪质量的重要因素.为了提高铝凝固温坪的复现水平,设计了三段控温固定点炉,利用金属外壳铝固定点容器,研究了垂直温场均匀性及其影响因素;在此基础上,采用连续热流密度法高精度复现了铝凝固点.实验结果表明:通过调整上部、中部、下部炉温的设置,可改善固定点炉温场均匀性,铝凝...     

用黑体辐射法复现铝凝固点

本文叙述用精密直流光电温度计昨现纯金属铝凝固点的实验装置和实验方法，复现铝凝固点的总不确定度小于50mK，置信度为99%。实验中对3个铝点黑体石墨坩埚容器的凝固温度进行了多次测量，3个容器的铝凝固点温度之差不大于10mK。在8个月的时间内，对同一铝点坩埚容器的铝凝固点温度进行了11次测量，其标准偏差为15mK，长期重复性也很好。     

便携式锡凝固点复现技术研究

以中国计量科学研究院最新研制的小型锡凝固点装置为基础,开展不同的凝固速率及诱导技术对锡凝固点温坪复现影响的研究,致力于获得适合本装置最优的复现技术.实验结果显示:两支室温下的石英诱导棒分别诱导60s左右,固定点炉温度设置在比温坪值低0.6K,能够获得较理想的温坪曲线,温坪时长约9h,复现性为0.18mk,扩展不确定度1.40mK(k =2)     

钠热管炉等温性的实验研究

为高精度地复现铝凝固点,中国计量科学研究院研制了钠热管炉。本文使用S型热电偶和Agilent公司3458A精密数字表测量了新研制钠热管炉的垂直温场。实验结果表明,在未放铝凝固点容器的情况下,炉温约645℃时,钠热管腔体轴向垂直温场最大温度变化不超过0．2℃。此外,找到了理想的放置固定点容器的等温区,为铝凝固点的复现创造了好的外部等温环境。     

银、铝、锌和锡凝固点的高精度复现

我们成功复现了90国家温标定义的固定点：银、铝、锌和锡凝固点。本文介绍了这些凝固点的是现方法和实验结果,表明能满足建立0－961．78范围内90国际温标的高精度复现系统的要求。     

铝凝固点及银凝固点容器国际关键比对评述

介绍了国际计量局（BIPM）温度咨询委员会（CCT）关键比对4即铝凝固点及银凝固点容器国际比对。采用固定点容器直接比对的形式进行，共11个国家实验室参加了该项比对，介绍了比对的组织、比对过程、实验方法以及参考值的选取，同时给出了比对结果及比对等效图。     

同轴等温钠热管的研制

为了改善高温固定点炉的等温特性以提高铝、银凝固定点的复现水平,中国计量科学研究院近年来开展了高温钠热管固定点炉的研究。而建立钠热管的制作系统并独立自主地研制钠热管是该研究的关键。在吸收国内外同行积累的宝贵经验的基础上,设计了一套新的高温钠热管制作系统,并利用该系统成功研制了适用于铝凝固点复现的同轴等温钠热管。本文将详细介绍高温钠热管的制作系统、研制步骤及制作工艺。     

复现银凝固点以上国际温标(ITS-90)

叙述中国计量科学研究院复现我国银凝固点以上国际温标(ITS-90)的原理、方法、仪器设备、实验结果、温标不确定度评定以及参加国际关键比对的初步结果.我国961.78℃～2200℃温度基准的扩展不确定度为0.10～0.65℃(置信水平p=0.99).1998年参加国际计量局温度关键比对,结果令人满意.     

复现银凝固点以上国际温标(ITS-90)

叙述中国计量科学研究院复现我国银凝固点以上国际温标 (ITS 90 )的原理、方法、仪器设备、实验结果、温标不确定度评定以及参加国际关键比对的初步结果。我国 961 78℃～ 2 2 0 0℃温度基准的扩展不确定度为 0 1 0～0 65℃ (置信水平p =0 99)。 1 998年参加国际计量局温度关键比对 ,结果令人满意。     

Johnson Noise Thermometry near the Zinc Freezing Point Using Resistance-Based Scaling

Johnson noise thermometry (JNT) is a primary method of measuring temperature which can be applied over wide ranges. The National Institute of Standards and Technology (NIST) is currently using JNT to determine the deviations of the International Temperature Scale of 1990 (ITS-90) from the thermodynamic temperature in the range of 505–933 K, overlapping the ranges of both acoustic gas-based and radiation-based thermometry. Advances in digital electronics have now made viable the computationally intensive and data-volume-intensive processing required for JNT using noise-voltage correlation in the frequency domain. The spectral noise power, and consequently the thermodynamic temperature T, of a high-temperature JNT probe is determined relative to a known reference spectrum using a switched-input digital noise-voltage correlator and simple resistance-scaling relationships. Comparison of the JNT results with standard platinum resistance thermometers calibrated on the ITS-90 gives the deviation of the thermodynamic temperature from the temperature on the ITS-90, T − T ₉₀. Statistical uncertainties under 50 μK·K⁻¹ are achievable in less than 1 day of integration by fitting the effects of transmission-line time constants over bandwidths of 450 kHz. The methods and results in a 3 K interval near the zinc freezing point (T _90-ZnFP ≡ 692.677 K) are described. Preliminary results show agreement between the JNT-derived temperatures and the ITS-90.     

A Determination of the Ratio of the Zinc Freezing Point to the Tin Freezing Point by Noise Thermometry

A Johnson-noise thermometer (JNT) has been used with a quantized voltage noise source (QVNS), as a calculable reference to determine the ratio of temperatures near the Zn freezing point to those near the Sn freezing point. The temperatures are derived in a series of separate measurements comparing the synthesized noise power from the QVNS with that of Johnson noise from a known resistance. The synthesized noise power is digitally programed to match the thermal noise powers at both temperatures and provides the principle means of scaling the temperatures. This produces a relatively flat spectrum for the ratio of spectral noise densities, which is close to unity in the low-frequency limit. The data are analyzed as relative spectral ratios over the 4.8 to 450 kHz range averaged over a 3.2 kHz bandwidth. A three-parameter model is used to account for differences in time constants that are inherently temperature dependent. A drift effect of approximately −6 μK·K⁻¹ per day is observed in the results, and an empirical correction is applied to yield a relative difference in temperature ratios of −11.5 ± 43 μK·K⁻¹ with respect to the ratio of temperatures assigned on the International Temperature Scale of 1990 (ITS-90). When these noise thermometry results are combined with results from acoustic gas thermometry at temperatures near the Sn freezing point, a value of T − T ₉₀ = 7 ± 30 mK for the Zn freezing point is derived.     

Evaluating the Inhomogeneity of Thermocouples Using a Pressure-Controlled Water Heat Pipe

There exists various research reports concerning the evaluation methods for the measurement uncertainty due to inhomogeneity of thermocouples; however, the universal method is still waiting to be established. This article considers the evaluation methods for the measurement uncertainty due to inhomogeneity of thermocouples based on comparison between results of two measurement methods. The first method is to estimate the uncertainty from the immersion characteristics of a thermocouple within a fixed-point furnace during its realization. The second method is to estimate the uncertainty from the immersion characteristics of a thermocouple within a heat-pipe furnace with a long uniform region. A pressure-controlled water heat-pipe furnace with an immersion depth of 1000?mm is developed to enable this work. It overcomes the technical difficulties that existed in applying conventional sealed heat pipes to such applications. From the immersion characteristics of a thermocouple measured by the above two methods, we have introduced three measurement parameters. Estimating the measurement uncertainty due to the inhomogeneity from our measurement results as examples is discussed.     

Automated Realization of the Triple Point of Water Using the Mush Method

In order to investigate mechanisms of phase transitions of supercooled water in a triple-point-of-water (TPW) cell when a mush method was used to create an ice mantle, an automated apparatus using small TPW cells was developed to obtain the TPW. In this article, the design principle, the apparatus, and the procedure for an automated formation of ice mantles in small TPW cells are described. Supercooled water in small TPW cells spontaneously transformed into uniform metastable dendritic crystals throughout the cells at supercoolings ranging from 5.85 °C to 8.77 °C and then changed into stable hexagonal closed-packed cellular crystals, forming an outer ice mantle from the outside inward. Some pertinent explanations based on thermodynamic solidification theory were used to describe the phase transition process in the mush method. In addition, the experimental results indicated that the realized temperatures of water in the small TPW cells were in good agreement within 0.1 mK approximately 6 h after the initial spontaneous crystallization had occurred. Finally, the small TPW cells (s/n 008 and s/n 001) were directly compared with a conventional TPW cell (s/n NIM-1-211); the temperature differences between the small TPW cells and the regular TPW cell were less than 0.21 mK.     

用锌凝固点和水沸点检定二等标准铂电阻温度计的扩展不确定度评定

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。     

用锑凝固点装置分度超短热电偶的研究

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.