传递水三相点容器在国际计量局的比对

国际计量局作为主导实验室组织了由20个国家计量标准实验室参加的CCT-K7水三相点容器国际关键比对.按照比对协议,参加者均选择了1个校准的传递容器送到国际计量局与两个共同的参照容器进行比对.介绍了国际计量局的比对,包括:冻制方法、实验装置、测量步骤、比对结果及相应的不确定度评定.比对结果表明:多数水三相点容器在0.15 mK范围内一致.     

VSMOW Triple Point of Water Cells: Borosilicate versus Fused-Quartz

To investigate an ideal container material for the triple point of water (TPW) cell and to reduce the influence to the triple-point temperature, due to the deviation of the isotopic composition of the water, both borosilicate and fused-quartz glass shelled TPW cells with isotopic composition substantially matching that of Vienna Standard Mean Ocean Water (VSMOW) were developed and tested. Through a specially designed manufacturing system, the isotopic composition, δD and δ¹⁸ O, of the water in the TPW cell could be controlled within ±10‰ (per mil) and ±1.5‰, respectively, resulting in control of the isotopic temperature correction to better than ± 8 μK. Through an ampoule attached to the cell, the isotopic composition of the water in the cell could be individually analyzed . After manufacture, the initial triple-point temperatures of the two types of cell were measured and compared to assess the quality of the cells and manufacturing process. Cells fabricated with the new system agree within 50 μK. Two innovatively designed borosilicate and fused-quartz TPW cells were made, each with six attached ampoules. One ampoule was removed every 6 months to track any changes in purity of the water over time.     

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)。     

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...     

一种快速冻制水三相点瓶的方法

水的三相点是热力学温度的唯一基准点,也是1990年国际温标(ITS-90)定义的最基本的、及其重要的固定点.水三相点的复现是通过水三相点瓶的冻制和保存来实现的,本文介绍了一种快速且实用的水三相点瓶冻制方法,并阐述了此种方法的优点.     

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。     

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.     

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.     

Establishment of a New National Reference Ensemble of Water Triple Point Cells

The results of the Bilateral Comparison EURAMET.T-K3.5 (w/VSL, The Netherlands) with the goal to link Switzerland’s ITS-90 realization (Ar to Al) to the latest key comparisons gave strong indications for a discrepancy in the realization of the triple point of water. Due to the age of the cells of about twenty years, it was decided to replace the complete reference ensemble with new “state-of-the-art” cells. Three new water triple point cells from three different suppliers were purchased, as well as a new maintenance bath for an additional improvement of the realization. In several loops measurements were taken, each cell of both ensembles intercompared, and the deviations and characteristics determined. The measurements show a significant lower average value of the old ensemble of \(0.59 \pm 0.25\hbox { mK }(k=2)\) in comparison with the new one. Likewise, the behavior of the old cells is very unstable with a drift downward during the realization of the triple point. Based on these results the impact of the new ensemble on the ITS-90 realization from Ar to Al was calculated and set in the context to performed calibrations and their related uncertainties in the past. This paper presents the instrumentation, cells, measurement procedure, results, uncertainties and impact of the new national reference ensemble of water triple point cells on the current ITS-90 realization in Switzerland.     

Vapor Pressure of Water at Its Triple Point

The vapor pressure of water at its triple point was measured with exceptionally high accuracy by realizing it with a special apparatus and measuring the pressure with the NBS precision mercury manometer. The vapor pressure apparatus had a system for circulating the liquid water. Actual triple point conditions were established with a thin sheet of freshly distilled liquid flowing down over an exposed mantle of ice frozen on a vertical well. This technique reduced non-volatile contaminants and the vapor was repeatedly pumped to remove accumulated volatile contaminants. A diaphragm pressure transducer was used to separate the water vapor from the helium used to transmit the pressure to the manometer. The value found for the vapor pressure of water at its triple point was 611.657 Pa with an uncertainty of ± 0.010 Pa from random errors, computed at 99 percent confidence limits. The systematic errors are estimated to be insignificant relative to the random errors.