The Discontinuity in the First Derivative of the ITS-90 at the Triple Point of Water

Rusby, R. L.

doi:10.1007/s10765-010-0794-9

Cited by 15 publications

(8 citation statements)

References 8 publications

(13 reference statements)

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“…However, our experimental uncertainty (±0.02 mK K −1 ) does not allow us to conclude that the discontinuity is significantly different from zero. Rusby [42] analysed the ITS-90 deviation coefficients of more than 40 SPRTs above and below T TPW , and found slope discontinuities that varied considerably, but had a negative bias.…”

Section: (B) Behaviour Near T Tpwmentioning

confidence: 99%

Estimates of the difference between thermodynamic temperature and the International Temperature Scale of 1990 in the range 118 K to 303 K

Underwood

Podesta

Sutton

et al. 2016

Phil. Trans. R. Soc. A.

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Using exceptionally accurate measurements of the speed of sound in argon, we have made estimates of the difference between thermodynamic temperature, T, and the temperature estimated using the International Temperature Scale of 1990, T90, in the range 118 K to 303 K. Thermodynamic temperature was estimated using the technique of relative primary acoustic thermometry in the NPL-Cranfield combined microwave and acoustic resonator. Our values of (T-T90) agree well with most recent estimates, but because we have taken data at closely spaced temperature intervals, the data reveal previously unseen detail. Most strikingly, we see undulations in (T-T90) below 273.16 K, and the discontinuity in the slope of (T-T90) at 273.16 K appears to have the opposite sign to that previously reported.

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Section: (B) Behaviour Near T Tpwmentioning

confidence: 99%

Estimates of the difference between thermodynamic temperature and the International Temperature Scale of 1990 in the range 118 K to 303 K

Underwood

Podesta

Sutton

et al. 2016

Phil. Trans. R. Soc. A.

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“…Although it is difficult to measure the slope discontinuity, in principle, it must arise in the ITS-90, i.e., in T 90 not in T . By evaluating the calibrations of over 40 capsule-type and long-stem SPRTs obtained over a period of more than 20 years, Rusby [44] has found discontinuities in the slope at the triple point between 0 × 10 −5 and 6 × 10 −5 . If new thermodynamic experiments are undertaken around TPW, the expected discontinuity is known as soon as the SPRT is calibrated.…”

Section: Analytical Smooth Interpolation Functionsmentioning

confidence: 99%

Present Estimates of the Differences Between Thermodynamic Temperatures and the ITS-90

Fischer

Podesta

Hill³

et al. 2011

Int J Thermophys

122

165

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At the request of the Consultative Committee for Thermometry (CCT), Working Group 4 (WG4) has critically reviewed all available measurements of the differences between thermodynamic and ITS-90 temperatures, (T − T 90 ), and documented the conversion of older data to the ITS-90. Particular attention has been given to the uncertainties. Based on this review, we provide consensus estimates of T − T 90 for selected measurements from 0.65 K to 1358 K. We provide two analytic functions for T − T 90 , one for use from 8 K to the triple point of water (T TPW ) and one for use above T TPW . The small discontinuity of the derivative dT 90 /dT at T TPW is discussed.J. Fischer (B) · L. Wolber PTB,We also identify temperature ranges where researchers are encouraged to undertake high-accuracy measurements of T − T 90 .

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“…The near constancy of S for each SPRT is a consequence of the SPRT resistance closely following Matthiessen's rule [15] ideal ( ) ( ) , R T R T R ' (22) where ideal ( ) R T is the resistance of ideally pure platinum, and R ' is a temperature-independent offset caused by impurities and vacancies. The same behavior is responsible for the observed correlations between SPRT resistance ratios at different fixed points e.g., [15][16][17][18][19], which are described by equations of the same form as (20). For the SRI to be zero for all pairs of subranges, the S values for any one SPRT should be the same at all fixed points.…”

Section: Snmentioning

confidence: 99%

“…The inconsistency between reference resistance ratios for fixed points above and below 0.01 ºC is also responsible for the discontinuity in the first derivative of T 90 at the triple point of water [17,20,21].…”

Section: Snmentioning

confidence: 99%

Some mathematical properties of the ITS-90

White¹

2013

AIP Conference Proceedings

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A new technique for direct traceability of contact thermometry Co-C eutectic cells to the ITS-90 AIP Conf. Proc. 1552, 352 (2013); 10.1063/1.4819565 Analysis of the ITS-90 inconsistency in overlap region of the mercury-gallium and the water-argon sub-ranges AIP Conf.Abstract. Investigations into uncertainty propagation on the standard platinum resistance thermometer (SPRT) subranges of the ITS-90 have yielded insights into some of the mathematical properties of interpolated scales. One of the key observations is that Type 3 non-uniqueness is amplified by the fixed-point sensitivity coefficients, which increases the importance of choosing interpolating functions that yield sensitivity coefficients with a limited magnitude. The use of complete polynomials for the interpolations is necessary to ensure consistent behavior of the scale for all SPRTs. This feature also ensures that linearly related variables such as the SPRT resistance R, the resistance ratio W, and the Cragoe Z variable, all give equivalent interpolations. Although, in principle, the choice of W r values is arbitrary, Type 1 non-uniqueness (subrange inconsistency) is influenced by the consistency of the set of reference resistance ratios, W r , assigned to the fixed points. Additionally, having dW r /dW close to unity simplifies the uncertainty propagation equations. Finally, the structure of ITS-90 lends itself to a separation of the attributes of reproducibility and thermodynamic accuracy, a feature not exploited in the development of ITS-90. The paper concludes with a suggested procedure for the design of scales of the same structure as ITS-90. Suggestions are also made for areas of investigation that may support future improvements to the temperature scale.

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The Discontinuity in the First Derivative of the ITS-90 at the Triple Point of Water

Cited by 15 publications

References 8 publications

Estimates of the difference between thermodynamic temperature and the International Temperature Scale of 1990 in the range 118 K to 303 K

Estimates of the difference between thermodynamic temperature and the International Temperature Scale of 1990 in the range 118 K to 303 K

Present Estimates of the Differences Between Thermodynamic Temperatures and the ITS-90

Some mathematical properties of the ITS-90

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