Considerations Relating to Type 1 and Type 3 Non-uniqueness in SPRT Interpolations of the ITS-90

Rusby, R. L.; Pearce, J. V.; Elliott, C. J.

doi:10.1007/s10765-017-2319-2

Cited by 11 publications

(18 citation statements)

References 8 publications

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“…Type 3 non-uniqueness (NU3). This conclusion is consistent with the recommendations of Rusby et al [53], but different to that recommended in [35,42], which suggests combining the uncertainties due to NU3 and SRI. A useful consequence of the conclusion and Rusby's recommendation is that subranges can be added to ITS-90 without compromising the uncertainty of other subranges, so long as the interpolations used in the new subranges do not introduce significant SRI.…”

Section: Nu3 Uncertainty In Its-90supporting

confidence: 86%

“…Certainly, for these two subranges, the average SRI is negligible compared to the interpolation error itself. The standard deviations of the peak SRI for each of five studies fall between 0.29 mK and 0.48 mK [53], which is of a similar magnitude to the uncertainties in the fixed-point realisations reported in the BIPM key-comparison database.…”

Section: Subrange Inconsistencysupporting

confidence: 65%

“…For the subranges in the temperature range between the mercury to aluminium fixed points, there are six ITS-90 interpolating equations leading to fifteen instances of overlaps, with each overlap having its own SRI. To date, most studies [37,[49][50][51][52] have investigated the SRI between the waterzinc and water-aluminium interpolations, as summarised in the appendix of [53]. The extreme value for the SRI occurs near 93 • C, and analysis from the five studies yields estimates of the mean maximum SRI ranging from −0.22 mK to +0.23 mK, while the mean of all studies is 0.1 mK.…”

Section: Subrange Inconsistencymentioning

confidence: 99%

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Standard platinum resistance thermometer interpolations in a revised temperature scale

White

Rourke

2020

Metrologia

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The thermal metrology community is considering revising the International Temperature Scale of 1990 (ITS-90), motivated by the opportunity to improve the thermodynamic accuracy, reproducibility, and ease of use of the scale, as well as health and safety concerns with the use of mercury in the current scale. This paper considers the mathematical structure of the standard platinum resistance thermometer (SPRT) interpolations of the ITS-90 and identifies (i) mathematical features that are advantageous and should be retained, (ii) opportunities for improvements, and (iii) the research required to maximise the benefits from such improvements. The improvements considered include minor adjustments that leave ITS-90 intact, numerical adjustments to reference resistance ratios that preserve the structure of ITS-90, fixed-point replacements, new subranges, and large-scale changes in the mathematical structure of the interpolations. A significant research effort will be required to implement some of the changes. Overall, an improvement in the thermodynamic accuracy by a factor of about ten is relatively easily realised, but improvements in reproducibility of the scale of even a couple of tens of percent will be hard won. For most users, the costs and inconvenience of a substantial scale revision may outweigh the benefits.

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Section: Nu3 Uncertainty In Its-90supporting

confidence: 86%

Section: Subrange Inconsistencysupporting

confidence: 65%

Section: Subrange Inconsistencymentioning

confidence: 99%

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Standard platinum resistance thermometer interpolations in a revised temperature scale

White

Rourke

2020

Metrologia

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“…In 2017 Rusby et al [8] reported the SRI between [TPW, Zn] and [TPW, Al] for a total of 159 NPL-calibrated SPRTs with a standard deviation of 0.41 mK and a mean of approximately −0.12 mK (excluding one outlier). Some dependence on the manufacture of the SPRTs was reported, which led to the small negative mean value.…”

Section: Past Investigations On Subrange Inconsistency Of Long-stem S...mentioning

confidence: 99%

Survey of subrange inconsistency of long-stem standard platinum resistance thermometers

et al. 2021

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The subrange inconsistency (SRI) of a large ensemble of long-stem standard platinum resistance thermometers (SPRTs), representative of worldwide production, has been investigated for all pairs of ITS-90 overlapping subranges between 83.8058 K and 933.473 K. The results are reported in terms of various statistical parameters to facilitate their comparison with the results of different authors, although a statistical test, applied to one specific pair of subranges, supported a Gaussian distribution of the results and justified the subsequent use of the mean and standard deviation as statistical parameters. Depending on the pair of overlapping subranges, the mean SRI as calculated varied from −1.23 mK to +0.21 mK and the SRI standard deviation varied from 0.04 mK to 0.62 mK. These numbers generally increased with the upper temperature limit of the pair of subranges, especially where the lower subrange requires a point which is not included in the upper subrange. The contribution to SRI from the fixed-point uncertainty propagation (PoU) was evaluated. The results showed that, although the effect of PoU on SRI largely cancels out for points common to both subranges, PoU still amounts to 59% to 130% of the differences between overlapping pairs of subranges. This means that the differences as calculated are probably a substantial overestimate of the true SRI. It is suggested that this effect is taken into account in making recommendations for typical uncertainties due to non-uniqueness.

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“…Several studies have been conducted to estimate the effects of SRIs caused by various subranges based on a number of SPRTs [4][5][6][7][8][9][10][11][12][13][14]. The water-zinc and water-aluminium subranges are the two widely used ones for SPRTs in ITS-90, and the SRIs caused by these subranges cannot usually be ignored because the overlapping range of 0.01…”

Section: Introductionmentioning

confidence: 99%

New interpolating equations of ITS-90 for SPRTs and HTSPRTs for the temperature range 419.527 ^°C–961.78 ^°C

Sun¹,

Li²,

Hao³

et al. 2020

Metrologia

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The subrange inconsistency (SRI) of the International Temperature Scale of 1990 (ITS-90) arises from the use of different interpolating equations for the same standard platinum resistance thermometers (SPRTs), called Type 1 non-uniqueness, and is a significant component of the uncertainty in the realization of the scale. In order to eliminate the SRI, new interpolating equations were proposed for the subranges 0.01• C to 660.323 • C and 0.01 • C to 961.78 • C, in which the subrange to the zinc point (419.527 • C) was extended using two additional terms without any overlap. This study investigated 30 SPRTs calibrated over the temperature range of 0.01 • C-660.323 • C and 19 high-temperature SPRTs (HTSPRTs) calibrated over 0.01 • C-961.78 • C at the National Institute of Metrology (NIM ). The feasibility of the proposed equations were evaluated by comparing them with the equations defined in ITS-90 and calculating the propagation uncertainties. The results show that the differences between the defined interpolating equations in ITS-90 and the proposed interpolating equations are generally within ± 0.4 mK for temperature range of 419.527• C-961.78• C, which is close to or less than the SRIs between the water-zinc and water-aluminium subranges. The propagated uncertainties of the proposed equations were within reasonable limits. It is concluded that these new interpolating equations can be taken as equivalent to the ITS-90 interpolating equations with the SRI eliminated.

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Considerations Relating to Type 1 and Type 3 Non-uniqueness in SPRT Interpolations of the ITS-90

Cited by 11 publications

References 8 publications

Standard platinum resistance thermometer interpolations in a revised temperature scale

Standard platinum resistance thermometer interpolations in a revised temperature scale

Survey of subrange inconsistency of long-stem standard platinum resistance thermometers

New interpolating equations of ITS-90 for SPRTs and HTSPRTs for the temperature range 419.527 ^°C–961.78 ^°C

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Considerations Relating to Type 1 and Type 3 Non-uniqueness in SPRT Interpolations of the ITS-90

Cited by 11 publications

References 8 publications

Standard platinum resistance thermometer interpolations in a revised temperature scale

Standard platinum resistance thermometer interpolations in a revised temperature scale

Survey of subrange inconsistency of long-stem standard platinum resistance thermometers

New interpolating equations of ITS-90 for SPRTs and HTSPRTs for the temperature range 419.527 °C–961.78 °C

Contact Info

Product

Resources

About

New interpolating equations of ITS-90 for SPRTs and HTSPRTs for the temperature range 419.527 ^°C–961.78 ^°C