ITS-90 Scale Realization on the New Radiation Thermometer Calibration Facility at NMi VSL

In the first half of 2005, Nederlands Meetinstituut Van Swinden Laboratorium B.V. (NMi VSL) redesigned their facilities for radiation thermometry in a new laboratory building and an opportunity arose to implement new measurement methods. The new facility is used for ITS-90 realization and dissemination in the temperature range from  − 50 °C to 3,000 °C. A study was performed to compare a silver-point realization with a fixed-point blackbody radiator (FP-BBR) to a sodium heat-pipe blackbody radiator (HP-BBR) traceable via a HTSPRT to a contact thermometry silver point. It was found that the fixed-point realization transfer to the sodium heat pipe results in an uncertainty from 0.2 K to 2.4 K for the ITS-90 over the temperature range from 961.78 °C to 3,000 °C.     

The Roles of the Mise en Pratique for the Definition of the Kelvin

The mise en pratique (“practical realization”) for the definition of the kelvin (MeP-K) was created by the Consultative Committee for Thermometry (CCT) in 2006 to give practitioners of thermometry a guide to the realization of the kelvin, i.e., measurement of temperature in kelvins, in accord with the International System of Units. In this article, the present and the future content of the MeP-K, the relationship of the MeP-K to other documents relevant to thermometry, the categorization of thermometry techniques in the MeP-K, and the benefits of proposed additions to the 2006 version of the MeP-K are discussed. The three categories of measurements within the MeP-K are: (1) primary methods for measuring thermodynamic temperature T; (2) formal approximations to T, in particular, the International Temperature Scale of 1990 (ITS-90) and the Provisional Low Temperature Scale from 0.9 mK to 1 K (PLTS-2000); and (3) indirect approximation methods that are neither primary nor defined on a temperature scale, yet capable of exceptionally low uncertainties or increased reliability. By providing a framework for primary methods and indirect methods, the MeP-K will foster development and application of new methods, such as the use of absolute radiometry or high-temperature fixed points. The MeP-K provides the CCT with a mechanism to update and to expand the thermometric methods in common use, without imposing on industry the high costs of changing the International Temperature Scale.     

Calibration of Radiation Thermometry Fixed Points Using Au/Pt Thermocouples

At NMIA, radiation thermometers are calibrated by comparison with a number of reference radiation thermometers which are themselves calibrated using fixed-point cells on the ITS-90 temperature scale (In, Sn, Zn, Al, Ag, and Au). The suitability of NMIA fixed-point cells used for standard platinum resistance thermometers (SPRTs) is evaluated by the comparison of ensembles of cells at each fixed point, and by participation in the international BIPM Key-Comparisons K3 and K4. However, the NMIA fixed-point cells used for radiation thermometry are typically much smaller (only 110 mm in length) and the thermowell length immersed in the metal much shorter (85 mm) than those used for SPRTs. Further, the insulation at the front of the crucible needs to accommodate the F/10 viewing cone of the radiation thermometers, so significant temperature gradients exist near the top of the crucible. As a consequence, the conduction errors obtained using SPRTs are too large to be of practical use. A convenient methodology based on the use of a Au/Pt thermocouple, together with a protective tube assembly to reduce conduction errors, has been developed. This allows the convenient measurement of the phase transition temperature traceable, at the 30 mK level, to the fixed-point cells used at NMIA to realize and maintain the ITS-90 scale. As the measurements are made in situ, the temperature environment, and hence the geometry and formation of the liquid?Csolid interface during melting and freezing, are similar to that occurring when used with radiation thermometers. Results are presented for ITS-90 fixed points up to Ag, establishing formal traceability of radiation thermometry fixed-point cells to NMIA??s primary ITS-90 cells.     

A matrix interpretation of the estimate of the extension of uncertainties when constructing a temperature scale

A matrix method of extending the uncertainties when constructing a temperature scale in the 0–660°C range using the calibration of a platinum resistance thermometer at fixed points and interpolating the temperature scale, using it in accordance with the ITS-90, is considered. __________ Translated from Izmeritel’naya Tekhnika, No. 7, pp. 41–45, July, 2006.     

替代汞三相点的研究和新温标展望

从国际温标ITS-90的定义固定点中替代汞三相点,是全球禁止汞的商业交易公约实施的必然结果,也是国际温度计量领域的一个研究热点.要达到替代的目标,候选替代物三相点温坪的计量性能必须达到汞三相点的水平,替代物三相点的复现装置成本可接受、复现技术不复杂;汞三相点被替代后,必然引起温标结构的改变.针对上述问题,对国际温度计量...     

Characterization of UME-Made Co–C Eutectic Fixed-Point Blackbody Cells

Eutectic phase transitions are commonly considered for use as fixed points in future 20XX temperature scales. Despite their potential as possible interpolation points in a high-temperature radiation thermometry scale (1000 °C and above), more studies on the reproducibility of the plateau temperature values are required. Various ongoing research projects on the long-term stability and reproducibility of the eutectic fixed points will likely improve the uncertainties enough to allow for their use as reference (or secondary) temperature points. In this article, the long-term reproducibility results of Co–C eutectic plateau realizations performed in the UME Radiation Thermometry Laboratory over four years, along with studies of the dependence on furnace heating/cooling rate and the short-term (1 day) repeatability, are presented. These measurements were performed with a monochromatic radiation thermometer calibrated according to ITS-90.     

A New Measurement Standard for the Interpolation and Transfer of a Temperature Scale in the 800–1600°C Range

The results of an investigation of a standard in the 800–1600°C temperature range are presented. The stability and reproducibility of the standard are determined, and a thermocouple is calibrated at fixed points of silver and copper, and also at higher temperatures using the pyrometer method. The investigations show the advantages of using this standard for the interpolation and transfer of a temperature scale compared with tungsten-strip lamps.     

Johnson Noise Thermometry near the Zinc Freezing Point Using Resistance-Based Scaling

Johnson noise thermometry (JNT) is a primary method of measuring temperature which can be applied over wide ranges. The National Institute of Standards and Technology (NIST) is currently using JNT to determine the deviations of the International Temperature Scale of 1990 (ITS-90) from the thermodynamic temperature in the range of 505–933 K, overlapping the ranges of both acoustic gas-based and radiation-based thermometry. Advances in digital electronics have now made viable the computationally intensive and data-volume-intensive processing required for JNT using noise-voltage correlation in the frequency domain. The spectral noise power, and consequently the thermodynamic temperature T, of a high-temperature JNT probe is determined relative to a known reference spectrum using a switched-input digital noise-voltage correlator and simple resistance-scaling relationships. Comparison of the JNT results with standard platinum resistance thermometers calibrated on the ITS-90 gives the deviation of the thermodynamic temperature from the temperature on the ITS-90, T − T ₉₀. Statistical uncertainties under 50 μK·K⁻¹ are achievable in less than 1 day of integration by fitting the effects of transmission-line time constants over bandwidths of 450 kHz. The methods and results in a 3 K interval near the zinc freezing point (T _90-ZnFP ≡ 692.677 K) are described. Preliminary results show agreement between the JNT-derived temperatures and the ITS-90.     

Possible Implications of the Principle of the ‘<Emphasis Type="Italic">Mise en Pratique</Emphasis>’ in its Application to the Kelvin

In 2005, the CIPM, in accepting CCT Recommendation T3, made a substantial change in the definition of the quantity ‘temperature’ by transforming the written standards for temperature (the “temperature scales”) into implementations of the mise en pratique of the kelvin. Having considered “that the creation of a formal mise en pratique of the definition of the kelvin would considerably simplify and clarify statements and recommendations of the CCT concerning the realization of the definition of the kelvin and the implementation of practical temperature scales,” the CIPM decision transformed the present ITS-90 and PLTS-2000 into two ways to implement the mise en pratique, with the possibility to further define “in due course” in the mise en pratique “recommendations concerning the direct determination of thermodynamic temperature.” The paper presents the author’s views regarding possible implications for the concept of a mise en pratique when applied to the kelvin beyond the present implementation. One possibility is to promote the formal use and status of realizations of the thermodynamic scale that, in practice, today only represents the physical basis of an empirical scale like the ITS-90. Another path arises from assuming that the only technical limit placed on the addition of further methods to the mise en pratique is that they be compatible with one another, to avoid ambiguities in the definition of the temperature values, though without the constraint of having the same, or comparable, accuracy. As a consequence, other scales that are currently considered ‘approximations’ to the ITS-90, with no formal status other than possibly being ‘recommended’ by some official body, such as the CCT WG2, could be upgraded to implementations of the mise en pratique, though with accuracy—and precision—inferior to that of the ITS-90. This would assist the vast majority of the users of temperature scales, and could be expected to increase the support of the worldwide thermal community for the work performed by the CCT. This possibility has so far been prevented by the need to define a single written standard at only the highest state-of-the-art accuracy level, the rest being left to sparse efforts, often devoid of traceability to the written standard.     

A Concerted International Project to Establish High-Temperature Fixed Points for Primary Thermometry

Research into high-temperature fixed points above 1,100°C has made significant progress since they were first reported in 1999. In particular, it has been established that single cells are repeatable at the sub-50 mK level, and intra-cell reproducibility at the 100 mK level has been demonstrated even at temperatures as high as 2,500°C. The fixed points have been used to compare temperature and radiometry scales over a wide temperature range, and are being developed and established as secondary references for thermocouple calibrations. However, before they can be fully accepted as primary temperature references, much work remains to be done, namely: (1) Establishment of long-term stability of the fixed-point temperature; (2) Development of robust procedures for the reliable construction of the fixed-point cells (to ensure routine intra-cell reproducibility of 100 mK); (3) Demonstration of long-term robustness of the fixed-point cells; (4) Assignment of thermodynamic temperatures to a selected set of fixed points; (5) Agreement and acceptance of these temperature values by the CCT; (6) Agreed methods on how to take full utility of these new fixed points into any future International Temperature Scale (ITS)—or the current ITS-90 via an addendum to the mise en pratique for the definition of the kelvin. To ensure that this work progresses to completion in a reasonable time frame, a research project, under the auspices of the CCT-WG5, has been formulated and is currently in progress with the aim of achieving the above mentioned targets by 2012. This article will describe this project and detail partner contributions.     

Preparative Steps Towards the New Definition of the Kelvin in Terms of the Boltzmann Constant

The International Committee for Weights and Measures (CIPM) approved, in its Recommendation 1 of 2005, preparative steps towards new definitions of the kilogram, the ampere, the kelvin, and the mole in terms of fundamental constants. Within the Consultative Committee for Thermometry (CCT), a task group (TG-SI) has been formed to consider the implications of changing the definitions of the above-mentioned base units of the SI, with particular emphasis on the kelvin and the impact of the changes on metrology in thermometry. The TG-SI has presented the results of its deliberations to the CCT and to the Consultative Committee for Units, CCU, and worked with them to prepare a report to the CIPM. This contribution, authored by the members of TG-SI, solicits input from the wider scientific and technical community on this important matter at the TEMPMEKO 2007 conference. For this purpose, the main details of the report to the CIPM are presented. The unit of temperature T, the kelvin, can be defined in terms of the SI unit of energy, the joule, by fixing the value of the Boltzmann constant k, which is simply the proportionality constant between temperature and thermal energy kT. Currently, several experiments are underway to determine k. The TG-SI is monitoring closely the results of all experiments relevant to the possible new definition of the kelvin, and has identified conditions to be met before proceeding with the proposed redefinition. The TG-SI considers that these conditions will be fulfilled before the 24th General Conference on Weights and Measures in October 2011. Therefore, the TG-SI is recommending a redefinition of the kelvin by fixing the value of the Boltzmann constant. A new definition of the kelvin in terms of the Boltzmann constant does not require the replacement of ITS-90 with an improved temperature scale nor does it prevent such a replacement. H. Ugur is the President, Consultative Committee for Thermometry (CCT).     

The standard function for a platinum resistance thermometer above the setting point of silver

A method and apparatus are described for measuring the characteristics W(T) at 962– 1085 °C for a hightemperature platinum resistance thermometer. A special design has been used containing a radiating cavity of black-body type localized around the sensitive element. The measurements were made with a spectropyrometric comparator by brightness comparison at the Ag, Au, and Cu reference points, and also at temperatures representing multiple and fractional brightnesses. The results are compared with the W(T) obtained by interpolating measurements made by the contact method at the Zn, Al, and Cu reference points. The differences in the W(T) constituted the temperature equivalent of 0.16, – 0.14, and 0.04 at the reference points correspondingly for Ag, Au, and Cu. The over- all measurement error is estimated as 0.19°C. An interpolation formula is proposed that is based on the standard function W_ref(T₉₀) given in the definition of ITS- 90.Translated from Izmeritel'naya Tekhnika, No. 9, pp. 39–42, September, 1993.     

Monochromator-Based Absolute Calibration of a Standard Radiation Thermometer

Centro Español de Metrología (CEM) is disseminating the International Temperature Scale (ITS-90), at high temperatures, by using the fixed points of Ag and Cu and a standard radiation thermometer. However, the future mise-en-pratique for the definition of the kelvin (MeP-K) will include the dissemination of the kelvin by primary methods and by indirect approximations capable of exceptionally low uncertainties or increased reliability. Primary radiometry is, at present, able to achieve uncertainties competitive with the ITS-90 above the silver point with one of the possible techniques the calibration for radiance responsivity of an imaging radiometer (radiance method). In order to carry out this calibration, IO-CSIC (Spanish Designated Institute for luminous intensity and luminous flux) has collaborated with CEM, allowing traceability to its cryogenic radiometer. A monochromator integrating sphere-based spectral comparator facility has been used to calibrate one of the CEM standard radiation thermometers. The absolute calibrated standard radiation thermometer has been used to determine the temperatures of the fixed points of Cu, Co–C, Pt–C, and Re–C. The results obtained are 1357.80 K, 1597.10 K, 2011.66 K, and 2747.64 K, respectively, with uncertainties ranging from 0.4 K to 1.1 K.     

Methods of Constructing an Individual Calibration Characteristic for Working Platinum Resistance Thermometers

Methods recommended for calibrating working platinum resistance thermometers are considered. A simplified method of constructing an interpolation curve in the form of second- and third-degree polynomials, calculated from the results of a calibration of thermometers at fixed points of the temperature scale, is proposed and investigated. It is shown that the error of the method lies within the limits of the error of temperature measurements made with working resistance thermometers in the 0–660°C range.     

Viscosity of aqueous NaCl solutions in the temperature range 25–200 °C and in the pressure range 0.1–30 MPa

New precise viscosity data are presented for aqueous solutions of NaCl; these data cover the temperature range 25–200 °C, the pressure range 0.1–30 MPa, and the concentration range 0–6 mol · kg^–1. The experimental precision is ±0.5%; a comparison of the present results with data available in the literature indicates that the accuracy of the present data is also of the order of ±0.5%. Two empirical correlations that reproduce the data within the precision are also given.     

The Dutch National Realization of the ITS-90 over the Range 13.8033 K–273.16 K

The facility constructed at NMi VSL to realize the ITS-90 in the capsule standard platinum resistance thermometer range (CSPRT, 13.8033–273.16K) is presented. To demonstrate the performance of our facility, the results of a recent measurement campaign are reported, in which 3 NMi VSL CSPRTs were calibrated in the range 13.8–273.16K at all of the fixed points required by the ITS-90. The uncertainty of the calibration of the CSPRTs at each of the fixed points is evaluated in accordance with the most recent recommendations of the Consultative Committee for Thermometry and its Working Groups 1 and 3.     

The Euramet Metrology Research Programme Project Implementing the New Kelvin (InK)

The kelvin, along with the ampere, kilogram, and the mole are likely to be redefined in terms of fundamental constants, in line with Conférence Générale des Poids et Mesures resolution 1 (2011), sometime before 2020. In advance of, and to support, the redefinition, a mise en pratique of the definition of the kelvin (MeP-K) is currently being prepared. The Euramet Metrology Research Programme Implementing the new kelvin (InK) project will coordinate research activity in this field with the objective of improving primary thermometry over the range from 0.0009 K to \({>}3000\,\mathrm{K}\) . Specifically, the project will aim to pursue the following three broad objectives: (1) Support the development of primary thermometry techniques for the realization and dissemination of thermodynamic temperatures, particularly at high \(({>}1300\,\mathrm{K})\) and low \(({<}1\,\mathrm{K})\) temperatures. This is a major objective of InK because primary thermometry methods at the extremes of temperature should, in principle, have lower uncertainties than defined scales. (2) Determine low uncertainty values of \(T -T_{90}\) in the temperature region where the defined scale is expected to continue providing the lowest uncertainties. This will support the development of the MeP-K and help in the construction of a reliable data set for any possible future temperature scale. (3) Use different thermodynamic thermometry methods to re-determine \(T-T_{2000}\) and therefore hopefully understand the cause of the discrepancy in the background data that constitutes the Provisional Low Temperature Scale of 2000 (PLTS-2000). An overview of the InK project, activities, and intended outcomes is given in this paper.     

Investigation of the interpolation relations for a platinum resistance thermometer over narrow temperature ranges

The systematic difference between the Callendar—Van Dusen function and the ITS-90 polynomial for working platinum resistance thermometers with different values of W(100) is analyzed and it is shown that this difference is not related to the purity of the platinum over a wide range of values of W(100), and depends considerably on the temperature range. A method of calculating the standard relations for platinum resistance thermometers is proposed based on a quadratic approximation of the ITS-90 function, and a method of constructing individual functions for platinum resistance thermometers in the 0–230°C range using a single calibrated point in addition to 0°C is described.Translated from Izmeritelnaya Tekhnika, No. 11, pp. 39–43, November, 2004.This is the last of the series of papers (of which the first was published in Izmeritelnaya Tekhnika No. 9, 2004), prepared from the proceedings of the Second All-Russia Conference on Problems of Thermometry Temperatura-2004, held in Obninsk in March 2004.     

A comparison of ideal and real moist air models for calculating humidity ratio and relative humidity in the 213.15 to 473.15 K range and up to a pressure of 1 MPa

This study evaluates how the ideal mixture model of moist air approximates a real mixture model when determining both humidity ratio and relative humidity for the 0.1- to 1-MPa pressure range and the -60 to 200°C temperature range. The relevant thermodynamic properties are calculated using, among others, a specific algorithm based on the relationships proposed by Hyland and Wexler corrected for the new ITS-90 temperature scale.