Automated system for measuring temperature profiles inside ITS-90 fixed-point cells

Hiti, M. A. Ei; Bojkovski, Jovan; Batagelj, V.; Drnovšek, J.

doi:10.1088/0957-0233/16/11/032

Cited by 7 publications

(4 citation statements)

References 4 publications

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“…A second unexplained problem with the triple point of water relates to the measured hydrostatic pressure gradient being higher than the theoretical value [31,32], although typically within the uncertainty. The deviation is weakly correlated with the diameter of the thermometer well [7], and is suppressed by the use of bushings, e.g., [28], so the cause may be related to convection effects.…”

Section: Pressure Effects In Fixed Pointsmentioning

confidence: 99%

Uncertainties in the SPRT Subranges of ITS-90: Topics for Further Research

White¹,

Ballico

Campo

et al. 2010

Int J Thermophys

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The CCT has completed the guide summarizing the uncertainties in the realization of the SPRT subranges of ITS-90 between the triple point of neon (24.5561 K) and the freezing point of silver (961.78 • C). This article identifies aspects of standard platinum resistance thermometry where either data or models are lacking and further research is required. In the calibration of SPRTs, the two main concerns are the need for data on liquidus slopes for the different impurities in the fixed points and improved understanding of the impact of the thermal environment of the fixed point on the realized temperature. In the use of SPRTs, the two largest sources of uncertainty are Types 1 and 3 non-uniqueness and oxidation. The causes of Type 3 non-uniqueness are not yet understood, especially at low temperatures, and there is a paucity of data for the high-temperature subranges. In respect of oxidation, there is a need for validation of the models developed in the 1980s, especially in light of the reduced partial pressure of oxygen used in modern SPRTs. A range of other effects including vacancy effects in SPRTs, isotopic effects in fixed points, and improved statistical methods are discussed.

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Section: Pressure Effects In Fixed Pointsmentioning

confidence: 99%

Uncertainties in the SPRT Subranges of ITS-90: Topics for Further Research

White¹,

Ballico

Campo

et al. 2010

Int J Thermophys

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“…The coil design of the thermometer sensor should not influence the results as long as its general characteristics are within the state-of-the-art limits and its immersion depth is sufficient. For the vertical positioning of the thermometer in the well, an automated positioning system with 0.1-mm accuracy was used [32]. The whole layout is presented in Fig.…”

Section: Measurementsmentioning

confidence: 99%

A numerical and experimental investigation of the heat losses in thermometric fixed-point cells

Batagelj

Žužek

Drnovšek

et al. 2015

International Journal of Heat and Mass Transfer

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“…The test is simple and may be performed without any special equipment, although a dedicated device for automated movement of thermometer has some additional advantages [8]. The test consists of raising the thermometer to a set of distances from the bottom of the cell and measuring the temperature at those immersion depths.…”

Section: Modeling the Immersion Profile And Bushings Testmentioning

confidence: 99%

Numerical Modeling of Heat Flux in Fixed-Point Cells Due to the Hydrostatic-Head Effect

2011

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The article presents the numerical analysis of a particular thermal effect, which occurs during the calibration of standard platinum resistance thermometers in fixed-point cells. The temperature within the fixed-point cell varies linearly with the immersion depth due to the hydrostatic-head effect, so a quasi-linear temperature gradient in the vertical direction is inherently present. If there is a temperature gradient, a resulting heat flux will appear. This heat flux flows across the thermal conductivities, which change with depth, so the resulting temperature field is distorted. The key issue that is tackled in this article is the magnitude of these temperature deviations and their influence on the measurement accuracy. This effect should not be confused with the perturbing heat exchange toward the thermal enclosure and ambient. These are independent effects that are in real systems superimposed on each other. To get a better insight into this phenomenon, a numerical model based on a finite-difference method was developed. The model allows the simulation of the measurement of the thermometer immersion profile and of the use of different bushings, as two of the methods for assessing the thermal effects. The results of the modeling showed that there is an inherent difference between the temperature measured by the thermometer sensor and the temperature at the point of the phase transition, even if the immersion depth was infinite and there was no perturbing heat exchange toward the thermal enclosure and ambient. Nevertheless, in several cases the thermometer would still almost perfectly follow the immersion-profile curve. The only exception is near the bottom of the cell, where a small deviation from the immersion profile was observed. This is in agreement

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Automated system for measuring temperature profiles inside ITS-90 fixed-point cells

Cited by 7 publications

References 4 publications

Uncertainties in the SPRT Subranges of ITS-90: Topics for Further Research

Uncertainties in the SPRT Subranges of ITS-90: Topics for Further Research

A numerical and experimental investigation of the heat losses in thermometric fixed-point cells

Numerical Modeling of Heat Flux in Fixed-Point Cells Due to the Hydrostatic-Head Effect

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