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1.
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
2.
A miniature metallic cell for the water triple point (TPW, temperature 273.16 K) was developed for capsule-type thermometer
calibrations for realizations with adiabatic calorimetry techniques. The LNE-INM/Cnam previously developed a copper cell for
the water triple point and the techniques for cleaning, filling, and sealing. On the basis of previous work, a new copper
cell prototype for the TPW was developed and filled at the LNE-INM/Cnam. Measurements were performed using an appropriate
calorimeter and a comparison block containing several thermometers. Preliminary results show a scatter of the temperatures
measured at the phase transition of the order of 0.2 mK when measurements are repeated over a short-term period (1 month).
A positive drift in the phase transition temperature of about 30μK·month−1 was observed over several months. Studies are in progress to improve the cell, to reduce the reproducibility uncertainty
to less than 0.1 mK and to have a phase transition with better temporal stability. 相似文献
3.
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)。 相似文献
4.
Isotopic analysis of the water used in KRISS triple point of water (TPW) cells was performed by three separate laboratories.
The δD and δ
18O isotopic composition of six ampoules, made from two TPW cells, were analyzed by isotope ratio mass spectrometers. The analysis
data showed that δD and δ
18O were − 62.17‰ and − 9.41‰ for the KRISS-2002-Jan cell, and − 36.42‰ and − 4.08‰ for the KRISS-2005-Jun cell. The temperature
deviation of the triple point of water for these cells calculated from Kiyosawa’s data and the definition of the TPW were
+ 45.07μK for the KRISS-2002-Jan cell, and + 25.49μK for the KRISS-2005-Jun cell. The KRISS TPW temperature was + 92μK higher
than the CCT-K7 KCRV after correcting for the deviation of the isotopic composition from Vienna Standard Mean Ocean Water. 相似文献
5.
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
6.
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
7.
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
8.
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
9.
10.
Jun Tamba Muneo Sakai Isao Kishimoto Masaru Arai 《International Journal of Thermophysics》2008,29(5):1749-1760
The twenty-one participating laboratories in the international key comparison of water-triple-point cells (CCT-K7) can be
classified into three groups: two laboratories that corrected the effect of the isotopic composition of water, four laboratories
that had information on the isotopic composition but did not correct the effect, and the remaining laboratories that had no
information. There were significant differences in the realized national standard for the triple point of water (TPW) between
those laboratories that applied the isotopic correction and those that did not. The isotopic correction is now considered
essential for the triple point of water. Since the National Metrology Institute of Japan (NMIJ) did not apply the isotopic
correction and estimated large uncertainties at the time of the CCT-K7 comparison, we subsequently developed new cells for
the TPW to improve the reliability and to reduce the uncertainty of the realization as a national reference. The isotopic
compositions of seven cells were analyzed, and a chemical impurity analysis of one cell was performed. The good consistency
among seven cells was shown in the results obtained when the isotopic correction was applied to the realized temperatures
measured experimentally. The expanded uncertainty of the new national reference of NMIJ is estimated to be 49 μK (k = 2), and as a result of this improvement, the expanded uncertainty for calibrating a water-triple-point cell is 80 μK. The
previous reference of NMIJ, reported in CCT-K7 to have an expanded uncertainty of 302 μK, is 42 μK lower than the new one.
The new reference value is within the uncertainty of the previous national reference, and the new uncertainty is completely
covered by the previous uncertainty. Furthermore, the new reference of NMIJ shows good agreement with the national references
of the six laboratories able to apply isotopic corrects to their results for CCT-K7. These facts confirm the validity and
the linkage to the CCT-K7 of both the previous and the new national references of NMIJ. 相似文献
11.
液氮冻制冰套法对水三相点温度的影响 总被引:3,自引:2,他引:3
介绍了液氮作为冷却剂在水三相点容器内冻制冰套的方法。利用该方法同时在两个不同真空度的水三相点容器内分别冻制冰套。通过实验,研究了此方法对所复现的水三相点温度的影响。实验结果表明:冻制过程中产生的应力以及开始生成的小冰晶引起水三相点温度偏低;并且,其对水三相点温度的影响随着水三相点容器内真空度的降低而增大。随着应力慢慢消除,小冰晶逐渐长大为大冰晶,所复现的水三相点值逐渐回升并趋于稳定。因此,为了高精度复现和准确测量水三相点,采用该冻制方法时,必须将冰套老化至少5天以后,才可以消除其对水三相点温度的影响。 相似文献
12.
E. Renaot Y. Hermier M. H. Valin G. Bonnier F. Adunka A. Van Der Linden M. Dobre M. Šmíd A. Bronnum T. Weckstrom E. Tegeler U. Noatsch M. Anagnostou E. Turzo-Andras S. Nemeth M. White P. Marcarino P. Steur A. Pauzha V. Augevicius M. de Groot J. Nielsen F. Helgesen W. Roszkowski E. Grudniewicz R. Kuna E. Filipe I. Lobo S. Gaita V. Chimenti J. Ivarsson S. Duris J. Ranostaj J. Bojkovski A. Steiner S. Ugur J. Gray S. Bruce R. Rusby D. Head 《International Journal of Thermophysics》2008,29(3):991-1000
The EUROMET.T-K3 comparison is the regional extension of CCT-K3. The comparison involved the six European national metrology
institutes (NMIs) previously involved in CCT-K3 (LNE-INM/CNAM, SMU, INRiM, NMi-VSL, NPL, PTB) and 18 additional European national
laboratories. The comparison was divided into five different loops, each coordinated by a co-pilot chosen from the laboratories
having participated in the CCT-K3 comparison. LNE-INM/CNAM played the role of pilot in linking the five loops. In each loop,
an artifact in the form of a standard platinum resistance thermometer (SPRT, 25 Ω) was circulated among the participating
laboratories. To have sufficient information about the possible drift of the SPRTs, the co-pilots performed a calibration
over the full temperature range at the beginning and at the end of the loop. A EUROMET reference value (ERV), taking into
account the whole comparison, was defined, and the differences (T
Lab − T
ERV) were calculated with the associated uncertainties. The method for establishing the link between the participants in CCT-K3
and in EUROMET.T-K3 is described.
Institut National de Métrologie (BNM-INM/CNAM at the time of the comparison, LNE-INM/CNAM since 1 January 2005), Paris, France. 相似文献
13.
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
14.
15.
16.
To improve the uncertainty of the aluminum fixed point, a study was launched by LNE-INM/CNAM in the framework of the EUROMET
Project 732 “Toward more accurate temperature fixed points” (Coordinating laboratory: LNE-INM/CNAM, 17 partner countries).
A new open cell was filled with aluminum of 99.99995% purity. A French laboratory carried out elemental analysis of the sample
using glow discharge-mass spectrometry (GD-MS). The values of the equilibrium distribution coefficient k and of the derivative of the temperature of the liquidus line with respect to the concentration of impurity i will be obtained through collaboration with a French physical and chemical laboratory. In the past, some aluminum cells were
opened after several melts and freezes. The aluminum ingot was sticking to the graphite crucible, indicating that physicochemical
reactions had likely occurred between Al and C. To avoid this reaction, an effort was made to draw benefit from the Al2O3 film that appears immediately on the surface of the aluminum ingot when it is exposed to oxygen. The open aluminum cell was
tested in different furnaces and with different thermal insulator arrangements inside the fixed-point assembly. The observed
drifts of the plateaux were always larger than the expected values. The cell was opened to inspect the aluminum ingot. The
ingot was extracted easily, since no sticking to the crucible had occurred. The aluminum showed a very bright surface, but
the presence of many “craters” throughout the thickness of the ingot was surprising. In some cases, the thermometer well was
even apparent. 相似文献
17.
In 2006, the CIPM clarified the definition of the kelvin by specifying the isotopic composition of the water to be used in the realization of the triple point. At the same time, the Consultative Committee for Thermometry gave recommended values for the isotopic correction constants to be used for water departing from the specified composition. However, the uncertainties in the values for the correction constants were undesirably large due to unresolved differences between the data sets from which the values were determined. This paper derives improved values of the constants by considering additional data from isotopic fractionation measurements and the heats of fusion and freezing points of the relevant water isotopologues. Values of the corrections determined from the expanded data are A D = 671(10) μK, A 18O = 603(3) μK, and A 17O = 60(1) μK. A typical correction made with these values lies just within the expanded uncertainty (k = 2) of the corrections made with the older values, but has about half the uncertainty. 相似文献
18.
M. Stevens R. Benyon S. A. Bell T. Vicente 《International Journal of Thermophysics》2008,29(5):1685-1695
In order to effectively implement the Mutual Recognition Arrangement (MRA) of the International Committee for Weights and
Measures (CIPM), national metrology institutes (NMIs) are required to support their claims of calibration and measurement
capability (CMC) with a quality system compliant with ISO/IEC 17025, and with suitable evidence of participation in key or
supplementary comparisons. The CMC review process, both at regional and inter-regional levels, uses criteria that combine
the provisions mentioned above, together with additional evidence demonstrating scientific and technical competence of the
institutes. For dew-point temperatures, there are key comparisons in progress under the Consultative Committee for Thermometry
(CCT) and under the European regional metrology organisation (EUROMET), together with information available on past regional
supplementary comparisons. However, for relative humidity there are, to date, no such comparisons available to support CMC
entries. This paper presents and discusses the results of a preliminary investigation of the use of relative humidity and
temperature transmitters in order to determine their suitability for the intercomparison of standard humidity generators in
support of CMC claims for the calibration of relative humidity instruments. The results of a recent bilateral comparison between
2 NMIs at the extremes of the range up to 98%rh at 70 °C, and down to 1%rh at −40 °C are reported. Specific precautions and
recommendations on the use of the devices as transfer standards are presented. 相似文献
19.
R. N. Kacker R. U. Datla A. C. Parr 《Journal of research of the National Institute of Standards and Technology》2003,108(6):439-446
Key comparisons carried out by the Consultative Committees (CCs) of the International Committee of Weights and Measures (CIPM) or the Bureau International des Poids et Mesures (BIPM) are referred to as CIPM key comparisons. The outputs of a statistical analysis of the data from a CIPM key comparison are the key comparison reference value, the degrees of equivalence, and their associated uncertainties. The BIPM publications do not discuss statistical interpretation of these outputs. We discuss their interpretation under the following three statistical models: nonexistent laboratory-effects model, random laboratory-effects model, and systematic laboratory-effects model. 相似文献
20.
A. Merlone F. Moro A. Castrillo L. Gianfrani 《International Journal of Thermophysics》2010,31(7):1360-1370
This article reports on the construction details of an isothermal cell, referenced to the triple point of water (TPW), together
with characterization of its temperature uniformity and stability. The traceability of the temperature measurements is also
defined and reported. The cell has an inner chamber of 15 mm diameter, and it is 150 mm long. Its temperature is actively
controlled and maintained stable within 0.1 mK, for an unlimited time. The temperature gradient is limited to less than one
millikelvin over the length of the cell which is kept in a horizontal position. This accurate temperature control is achieved
by means of a series of three vacuum chambers, one inside the other. A special heater, reflectors, standard platinum resistance
thermometers, several feedthroughs, an auxiliary thermostat, specific electronics, and dedicated software are used for the
active control. The device represents a mixture of cryogenic and contact thermometry techniques, and it has been designed,
assembled, and characterized at the Istituto Nazionale di Ricerca Metrologica. This temperature-stabilized cell is a part
of a more complex experimental setup, based on near-infrared precision laser spectroscopy, devoted to the experimental determination
of the Boltzmann constant. 相似文献