两种不同的冰套冻制方法——固态干冰法、低温热管法

本文介绍了两种不同的冰套冻制方法———固态干冰法和低温热管法。采用这两种方法分别在两个水三相点容器内冻制冰套 ,通过实验研究冻制方法对水三相点温度的影响。实验结果表明 :这两种冻制方法对水三相点温度的影响非常小 ,即两个水三相点容器所复现的水三相点温度在± 0 .0 4mK范围内一致     

两种不同的冰套冻制方法--固态干冰法、低温热管法

本文介绍了两种不同的冰套冻制方法--固态干冰法和低温热管法.采用这两种方法分别在两个水三相点容器内冻制冰套,通过实验研究冻制方法对水三相点温度的影响.实验结果表明这两种冻制方法对水三相点温度的影响非常小,即两个水三相点容器所复现的水三相点温度在±0.04mK范围内一致.     

金属外壳水三相点容器

水三相点是ITS-90国际温标中最重要的定义固定点,其复现不确定度是传递到整个温标的.目前,通常采用不同的冻制方法在硼硅玻璃或石英水三相点容器内冻制均匀的冰套来复现水三相点.冻制过程中,由于在水三相点容器内生成冰桥,会造成容器的破裂.为了解决此难题,研制了金属外壳水三相点容器,利用高纯水自发相变原理,在液体槽内自动冻制...     

水三相点瓶冰套冻制方法的探索

水三相点是定义热力学温度单位的唯一参考点,也是ITS-90国际温标最重要的定义固定点。水三相点的复现是通过水三相点瓶内冻制冰套来实现。文章首先介绍了几种传统的冰套冻制方法,其次讨论了其优缺点;最后着重介绍了一种快速简单可行的冻制冰套的新方法,并阐述了此种方法的优点。     

不同来源的水三相点容器的比对

本文介绍了水三相点在开尔文热力学温度和ITS-90国际温标中的重要地位.重点介绍了麦克劳式水三相点容器内冰套的冻制方法及水三相点的复现.同时,NIM与ISOTECH同种结构的水三相点容器进行比对.比对结果表明,不同来源的水三相点容器复现的水三相点值在±0.04mK范围内一致.     

不同来源的水三相点容器的比对

本文介绍了水三相点在开尔文热力学温度和ITS-90国际温标中的重要地位。重点介绍了麦克劳式水三相点容器内冰套的冻制方法及水三相点的复现。同时,NIM与ISOTECH同种结构的水三相点容器进行比对。比对结果表明,不同来源的水三相点容器复现的水三相点值在±0.04mK范围内一致。     

水三相点瓶自动冻制保存装置复现性研究

介绍了型号为CIMM-TH-0230的水三相点瓶自动冻制保存装置,对该装置进行水三相点温坪复现性研究,并考核装置的各项指标。实验结果显示:该装置冻制的水三相点的温坪在48 h内变化不大于0.2 m K,复现性小于0.04 m K,稳定性优于0.5 m K,不同瓶子之间复现的温度差值不大于0.4 m K。试验数据表明该装置非常适合水三相点瓶的自动冻制、保存与复现。     

论一种恢复水三相点容器性能的方法

本文介绍了在研究水三相点容器长期可靠性能的实验中，国外所采用的一种恢复水三相点容器性能的方法。我们利用此方法制作两组容器，通过对照实验研究此方法对水三相点温度的影响。实验结果表明：由于此方法不能最大程度除去溶解在容器水中、吸附在容器内壁面的气体，导致所复现的水三相点温度偏低约0．13mK。     

论一种恢复水三相点容器性能的方法

本文介绍了在研究水三相点容器长期可靠性能的实验中 ,国外所采用的一种恢复水三相点容器性能的方法。我们利用此方法制作两组容器 ,通过对照实验研究此方法对水三相点温度的影响。实验结果表明 :由于此方法不能最大程度除去溶解在容器水中、吸附在容器内壁面的气体 ,导致所复现的水三相点温度偏低约 0 13mK。     

环境对水三相点温度的影响

本文通过实验研究了环境对水三相点温度的影响。实验结果表明 ,当环境温度为 2 0 5℃ ,环境热辐射引起所测量的水三相点值偏高约 0 1 4～ 0 1 7mK ;热辐射对水三相点温度的影响随着热辐射强度的增强而增大 ;在高精度复现、准确测量水三相点时 ,用黑布罩住温度计及水三相点容器口 ,可以消除环境热辐射的影响。     

Behavior of Triple-Point-of-Water Cells for Different Sizes of the Ice Mantle

The effect of differences in the amount of ice mantle on the realization temperature of the triple point of water (TPW) was investigated. Three TPW cells were used in the experiment as the TPW cell under test. These TPW cells were manufactured at different times. An ice mantle was prepared for each cell, and the amount of these ice mantles was changed when the ice mantle was re-prepared. Comparison measurements were carried out between a standard TPW cell and the three cells under test, and the temperature difference was measured. As a result, although an identical TPW cell was used, a change in the temperature difference was observed when the amount of ice mantle was different. In the case of the TPW cell that was manufactured 30 years ago, the observed temperature change was larger than 0.1 mK. It is considered that the principal cause is the dissolution of glass elements from the TPW cell.     

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.     

Analysis of the Comparison of TPW Realizations in Europe in Light of CCT Recommendation 2 (CI-2005)

Three comparisons of different triple-point-of-water (TPW) realizations in Europe have been organized under the auspices of EUROMET (EUROMET Projects 278, 549, and 714). Thirty European national metrology institutes were involved in these three comparisons that took place from 1994 to 2005. The aim of these successive projects was to assess the uncertainties associated with the practical realization of the triple point of water in Europe. Fifty-four TPW local cells were compared to a traveling standard cell (ref 679) circulated with an isothermal enclosure. The same equipment was used for the three projects, and LNE-INM regularly checked the stability of the TPW standard cell. Recently, LNE-INM has devoted efforts to bring the French standard at the triple point of water into close agreement with CIPM Recommendation 2 (CI-2005). The isotopic fractionation between water and ice when the cell is in use was experimentally studied. Several new TPW cells delivered by the manufacturer with water samples were added to our batch of reference cells. A French laboratory analyzed the isotopic compositions of these samples. These actions allow the French national definition of temperature at the triple point of water to be changed. A new temperature was associated with TPW cell 679 in agreement with the CIPM recommendation. In this presentation, the latest TPW cell measurements carried out by LNE-INM are presented. The results from EUROMET Projects 278, 549, and 714 are investigated in light of these changes.     

Implementing a New Group of TPW Cells as National Standard: Impact on Calibration Services

The definition of the kelvin is based on the triple-point temperature of highly pure water having the isotopic composition of ocean water (more specifically, the isotopic composition is equivalent to that of VSMOW). Belgian national metrology realizes the triple point of water (TPW) as the mean of temperatures measured in three sealed cells. In order to take into account the isotopic composition effect on TPW temperature, the ensemble of cells was replaced in 2006. Three new cells, with isotopic analysis of the contained water, were bought from different manufacturers. The new group of cells was compared to the old TPW national realization in order to quantify the effect of moving towards a new reference. Two different standard thermometers were used in all the cells to take 10 daily measurements on two different ice mantles. The measured resistances were corrected for hydrostatic head, self-heating, and isotopic composition (when available) before calculating the difference. A difference of about 87 μK was found between the old and the new national references. This difference is transferred to customers’ thermometers and cells through calibrations, and the change has to be documented in each new calibration certificate. An additional consequence of the new ensemble cell implementation is the significant reduction in the spread of deviations of individual cells from the mean temperature. The maximum difference between two cells of the ensemble is 96 μK for the old reference cells and 46 μK for the new reference cells corrected for isotopic composition effects.     

4种不同水源的水三相点容器的比对

为了研究水源对水三相点温度的影响,采用4种不同的水源并按照相同的制作工艺研制高质量的水三相点容器.同时,将这些容器进行了比对实验.比对结果表明:这些不同水源的水三相点容器复现的水三相点值在±0.02 mK范围内一致.故推断出水源对水三相点温度的影响很小.     

The Impact of Isotopic Concentration,Impurities, and Cell Aging on the Water Triple-Point Temperature

In 2005, the National Institutes of Standards and Technology (NIST) and Fluke’s Hart Scientific Division initiated a study to validate the isotopic correction algorithm applied to the realization temperature of triple point of water (TPW) cells. Additionally, the study quantified the impact of water sample impurities on the TPW cell realization temperature. For this study, eight TPW cells containing water of the same nominal isotopic concentration as Vienna Standard Mean Ocean Water (VSMOW) were used. Five of the cells were manufactured with fused-quartz envelopes and the remaining three with borosilicate envelopes. One TPW cell of each type was uniquely designed so that water samples could be periodically removed to analyze the isotopic composition and to monitor any changes in water purity with time and thereby correlate changes in composition with changes in realization temperature. The borosilicate TPW cells gave an average drift of −13 μK · yr⁻¹ and the more stable fused-quartz TPW cells gave an average drift of −2 μK · yr⁻¹.     

Effect of Impurities on the Triple Point of Water: Experiments with Doped Cells at Different Liquid Fractions

Recent international comparisons showed that there is still room for improvement in triple point of water (TPW) realization uncertainty. Large groups of cells manufactured, maintained and measured in similar conditions still show a spread in the realized TPW temperature that is larger than the best measurement uncertainties (25 µK). One cause is the time-dependent concentration of dissolved impurities in water. The origin of such impurities is the glass/quartz envelope dissolution during a cell lifetime. The effect is a difference in the triple point temperature proportional to the impurities concentration. In order to measure this temperature difference and to investigate the effect of different types of impurities, we manufactured doped cells with different concentrations of silicon (Si), boron (B), sodium (Na) and potassium (K), the glass main chemical components. To identify any influence of the filling process, two completely independent manufacturing procedures were followed in two different laboratories, both national metrology institutes (VSL, Netherlands and UME, Turkey). Cells glass and filling water were also different while the doping materials were identical. Measuring the temperature difference as a function of the liquid fraction is a method to obtain information about impurities concentrations in TPW. Only cells doped with 1 µmol·mol^?1 B, Na and K proved to be suitable for measurements at different liquid fractions. We present here the results with related uncertainties and discuss the critical points in this experimental approach.     

CCT-K7水三相点容器国际关键比对

在国际互认框架内，国家计量标准的国际等效性是通过国际计量委员会（CIPM）的咨询委员会组织的一系列国际关键比对来确定的。温度咨询委员会（CCT）委托国际计量局（BIPM）作为主导实验室组织了由20个国家实验室参加的CCT-K7水三相点容器国际关键比对。比对结果表明：这些国家基准水三相点值在0．171mK范围内一致。此外，为了减小国家实验室复现水三相点的系统差，需要进一步研究同位素组成对水三相点温度的影响以及同位素修正。     

高准确度水三相点容器

水三相点的高精度复现及准确测量是保证国际温标ITS-90实施的关键。水三相点容器内高纯水的同位素组成会影响复现的水三相点温度值。为了提高水三相点复现水平,减小氢氧同位素的影响,研制了带有氢氧同位素分析的石英及硼硅玻璃高准确度水三相点容器。为了评价容器的性能,开展了硼硅玻璃和石英水三相点容器的比对。实验结果表明:同位素修正前,石英玻璃和硼硅玻璃水三相点容器复现的水三相点在0.058mK范围内一致;同位素修正之后,容器之间的差异在0.017mK范围内一致。采用高准确度水三相点容器复现水三相点的扩展不确定度为0.066mK(k=2)。