Comparison of realizations of the thermometric fixed points of the ITS-90 in the range  38  C to 420  C between Canada and Mexico

Ancsin, J; Méndez-Lango, E.

doi:10.1088/0026-1394/33/4/18

Cited by 3 publications

(7 citation statements)

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“…These values are also given in Tables 2 to 5. (The resistance of the PRT at the run-off point was consistently reproducible within a fraction of 1 mK [2]. )…”

Section: Zn Sn and Inmentioning

confidence: 84%

“…As pointed out in [2], the temperature difference between two cells realizing a given fixed point can be determined by…”

Section: Comparison Methodsmentioning

confidence: 99%

“…In 1996 a pragmatic rather than esoteric approach was taken. Fixed points, as used for routine calibration of PRTs, without any special treatment of either the fixed points or the PRTs, of the Centro Nacional de Metrología (CENAM, Mexico), and the NRC were compared using a set of portable cells [2]. In this work, the irrelevance of accurate determinations was discussed in detail, using method B.…”

Section: Comparison Methodsmentioning

confidence: 99%

“…Some of the fixed points were compared via the fixed points of the portable calibration apparatus developed at the NRC a number of years ago. It consists of a small furnace, that could be carried as "on board" luggage, together with a set of metal-clad open cells of Zn, Sn, In, Ga and (sealed) Hg [2]. A small sample of Al (66 g) in its quartz housing units, similar to that described in [3], was also carried to be used in a furnace of the host laboratory.…”

Section: About the Comparisonmentioning

confidence: 99%

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Comparing fixed points of the ITS-90 as realized in Canada, Argentina and Brazil

et al. 2001

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“…These values are also given in Tables 2 to 5. (The resistance of the PRT at the run-off point was consistently reproducible within a fraction of 1 mK [2]. )…”

Section: Zn Sn and Inmentioning

confidence: 84%

“…As pointed out in [2], the temperature difference between two cells realizing a given fixed point can be determined by…”

Section: Comparison Methodsmentioning

confidence: 99%

Section: Comparison Methodsmentioning

confidence: 99%

Section: About the Comparisonmentioning

confidence: 99%

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Comparing fixed points of the ITS-90 as realized in Canada, Argentina and Brazil

et al. 2001

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“…A portable calibration laboratory, developed at the NRC a few years ago, consisting of two sets of small cells (2.5 cm diameter and 22.5 cm high) and a small furnace (20 cm 30 cm 35 cm high, accommodating all cells except Hg), was used to compare the fixed points [1]. The cells of one set are metal-clad graphiteencased (for industrial use) and those of the other set are sealed in quartz (for laboratory use).…”

Section: Introductionmentioning

confidence: 99%

The reproducibility of some thermometric fixed points and the accuracy of temperature measurements using platinum resistance thermometers

Ancsin¹,

Méndez-Lango²

1999

Metrologia

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The reproducibility of some thermometric fixed points and the accuracy of four platinum resistance thermometers (PRTs) were studied. It was found that the fixed points of aluminium (Al), zinc (Zn), tin (Sn), indium (In) and gallium (Ga) were realized reproducibly within ± 0.17 mK; ± 0.11 mK; ± 0.10 mK; ± 0.13 mK and ± 0.12 mK, respectively. Because the actual impurities and their concentration in our samples (of 99.9999 % or 99.999 99 % purity) are unknown, the systematic uncertainty due to impurities cannot be estimated. However, any of the samples of Ga, In, Sn, Zn and Al is consistent with the rest within ± 0.2 mK, using a cubic or quadratic deviation function, in the temperature range 0 C to 660 C. This indicates that the effect of impurities is negligible.Four PRTs were selected at random. They were calibrated repeatedly, first up to the Zn point and then up to the Al point. The resistance of each PRT drifted. From time to time, for each PRT, a seemingly well-established resistance drift suddenly and unpredictably changed to a different rate of drift. Occasionally, the resistance of the PRTs shifted. Such unpredictable changes obviously limit the accuracy of temperature measurements using PRTs no matter what the accuracy of their calibrations. In the case of our four PRTs, the uncertainty of temperature measurements near 660 C ranged from about ± 1 mK to about ± 2.5 mK even though they were all calibrated at all fixed points well within ± 0.25 mK uncertainty. Possible explanations are offered for the apparently permanent drifts and the erratic shifts in the resistance of the PRTs. Some comments are made concerning the ambiguity of "immersion tests" in general. The furnaces of the National Research Council of Canada used in this work are high-temperature adiabatic calorimeters.

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ITS-90: the instability of the Al point

Ancsin

2003

Metrologia

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Experiments, described below, revealed certain shortcomings of the current definition of the Al point: pressure in sealed type Al cells made of quartz was observed prior to their sealing and was found to steadily decrease. Consequently, the realized Al points using sealed quartz cells are in a state of drift. In addition, the initial Al point values yielded by open cells are higher than the subsequently realized ones: five different gases were used to apply the initial 1 atm pressure over the Al samples (air, N 2 , Ar, He, CO 2 ). Each of them appeared to contaminate slightly the Al samples, lowering the initial value of the Al point by 1 or 2 mK. However, sealed quartz triple point cells remained stable at their initial value indefinitely. Thus, the triple point of Al is a more reliable fixed point than the defining Al freezing point itself.

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Comparison of realizations of the thermometric fixed points of the ITS-90 in the range 38 C to 420 C between Canada and Mexico

Cited by 3 publications

References 1 publication

Comparing fixed points of the ITS-90 as realized in Canada, Argentina and Brazil

Comparing fixed points of the ITS-90 as realized in Canada, Argentina and Brazil

The reproducibility of some thermometric fixed points and the accuracy of temperature measurements using platinum resistance thermometers

ITS-90: the instability of the Al point

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