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CCT-K7水三相点容器国际关键比对 总被引:1,自引:1,他引:0
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。 相似文献
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本文介绍了为研究因不同区域海洋中海水的氧、氢同位素存在的差异对水三相点温度的影响而采用的方法。即选取两种不同水域的天然海水,按照相同的工艺制作水三相点容器,采用相同的方法复现水三相点,然后通过容器间的比对进而研究其对水三相点温度的影响。比对结果表明,利用此法制作的水三相点容器复现的水三相点温度在±0.04mK范围内一致,且水三相点的复现性均优于0.05mK。 相似文献
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不同来源的水三相点容器的比对 总被引:1,自引:0,他引:1
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. 相似文献
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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. 相似文献
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介绍了与标准平均海水同位素(VSMOW)成分相近的石英水三相点瓶的研制过程和试验分析结果.利用新的制作工艺,所有水三相点瓶的同位素成分δD和δ18O可被分别控制在±10‰和±1.5‰之内,这样即使没有进行同位素修正,由同位素成分与VSMOW的偏离对温度的影响仍可控制在±8μK之内.如果对某个水三相点容器的同位素成分单独分析,并用分析结果对水三相点温度值进行修正,则由上述因素对温度的影响可控制在±3μK之内.实验结果表明,硼硅玻璃水三相点瓶的年漂移约为-13μK,而石英水三相点瓶年漂移约为-2μK,因此,石英水三相点瓶比硼硅玻璃水三相点瓶的性能更加优越. 相似文献
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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. 相似文献
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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. 相似文献
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K. Kodaira 《International Journal of Thermophysics》2011,32(11-12):2261-2268
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. 相似文献
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K. D. Hill 《International Journal of Thermophysics》2014,35(3-4):611-619
Contamination of triple-point-of-water (TPW) cells by the chemical components of the borosilicate glass that contains the water is now widely recognized as the principal contributor to long-term drift of the cell temperature. To add to the available experimental data, a comparison of 24 TPW cells of various ages (from 10 years to 59 years), manufacturers (NRC, Jarrett, Isotech), and materials (borosilicate glass and fused quartz) was undertaken in 2013. Twelve cells from this group were compared to one another in 1997. By comparing the current inter-cell temperature differences to those determined 16 years earlier, it was found that some cells have remained stable, others have become colder (as might be expected from ongoing dissolution of the glass), and one or two show an apparent increase in temperature that seems anomalous. Also included among the 24 cells are five cells of borosilicate glass and five of fused quartz that were purchased 10 years ago. By comparing the relative temperature differences among this group of borosilcate and fused-quartz-encapsulated cells to the values obtained when they were last compared 6 years ago, it was found that the average temperature of the borosilcate group of cells decreases by \(-6\,\upmu \mathrm{K}\,{\cdot }\,\mathrm{year}^{-1}\,({\pm }2\,\upmu \mathrm{K}\,{\cdot }\,\mathrm{year}^{-1})\) , in reasonable agreement with an average drift of \(-4\,\upmu \mathrm{K}\,{\cdot }\,\mathrm{year}^{-1}\) suggested 12 years ago. It was concluded that fused quartz is the superior container for TPW cells. 相似文献
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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. 相似文献
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Miruna Dobre 《International Journal of Thermophysics》2008,29(3):799-807
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. 相似文献
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M. Dobre A. Peruzzi M. Kalemci J. Van Geel M. Maeck A. Uytun 《International Journal of Thermophysics》2018,39(5):60
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. 相似文献