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Temperature measurement of stored nuclear waste is important for long-term monitoring. Conventional sensors can degrade in ionizing radiation from induced transmutations and their frequent replacement is inconvenient. A thermometer based on suitable phosphors can overcome some problems, but the optical signal needs to be transmitted through an optical fibre and processed remotely away from the dangerous area. This requires that the optical fibre itself be suitably resistant to radiation-induced damage. Here, we report transmission measurements through a type of hollow-core fibre based on anti-resonance and with transmission windows at wavelengths suitable for use with the thermographic phosphor magnesium fluorogermanate whilst subjected to gamma radiation. Its performance is compared to commercially available standard fibres (single mode and radiation hard fibres) at dose rates equivalent to decades of use in a storage facility. Transmission was unchanged for the anti-resonant fibre at the phosphor emission wavelength and it was successfully incorporated into a fibre thermometer that worked from 20 ∘ C to 200 ∘ C . Performance at the phosphor excitation wavelength needs to be improved by modification to the hollow-core fibre design, but we show that a hybrid of single mode and anti-resonant fibres can already be made into a thermometer with suitable gamma immunity. [ABSTRACT FROM AUTHOR]

Oral cancer is the world's sixth most prevalent form of cancer and tongue is the most common site in oral cancer. Here, we report the feasibility of contact thermometry for the identification of tongue tumour at its early stage. The thermal and geometrical tumour parameters were predicted by contact temperature measurements of the tongue in a closed mouth. A suitable thermal sensor arrangement had been developed for obtaining the temperature distribution of the tongue. A computational method had been modelled for estimating tumour parameters using limited number of discrete temperature data. Heat transfer in the closed mouth had been modelled using Pennes bio heat transfer equation and the parameter optimization had been carried out using Levenberg–Marquardt (LM) method. The sensor array developed could identify the subtle change in temperature due to tumour in the tongue. The tongue having tumour showed a maximum variation of 0.4 K in the surface temperature. The geometrical and thermal parameters of tumour were simultaneously estimated with 88 % accuracy. Upon adding a random error of ± 1 % to the simulated temperature data, no significant changes were observed in the estimation. The tumour parameter estimation methodology shows that high metabolic heat generation and high blood perfusion source term indicates the presence of tumour. The predicted location and the size of the tumour can be used for pathological investigations. We propose that a wireless wearable system integrated with thermal sensors can be used for monitoring tongue surface temperature and eventually, the early detection of tongue cancer. [ABSTRACT FROM AUTHOR]

Accurate temperature measurements are critical in manufacturing, affecting both product quality and energy consumption. At elevated temperatures, non-contact thermometers are often the only option. However, such instruments require prior knowledge of the surface emissivity, which is often unknown or difficult to determine, leading to large errors. Here we present a novel imaging luminescence thermometer based on the intensity ratio technique using magnesium fluorogermanate phosphor, with the potential to overcome this limitation. We describe measurements performed on a number of engineering alloys undergoing heat treatment at temperatures of up to 750 °C and compare these measurements against a traditional contact thermocouple and thermal imager system. Agreement between the luminescence and embedded thermocouple temperatures was found to be better than 45 °C at all temperatures. However, the thermal imager measurement on the bare metal samples, with the instrument emissivity set to 1.0, showed differences of up to 500 °C at 750 °C, a factor of 10 larger. In an effort to improve the thermal imager accuracy, its instrument emissivity was adjusted until its temperature agreed with that of the thermocouple. When measuring on the bare metal, the effective emissivity was strongly sample dependent, with mean values ranging from 0.205 to 0.784. Since the phosphor derived temperatures exhibited substantially smaller errors compared to the thermal imager, it is suggested that this method can be used to compliment the thermal imaging technique, by providing a robust mechanism for adjustment of the instrument emissivity until agreement between the thermal imager and phosphor thermometer is obtained. [ABSTRACT FROM AUTHOR]

The freezing temperatures of two different, high-purity (nominal purity of 99.9999 %) zinc samples were realized, and the dissolved impurities were analyzed at three independent Glow Discharge Mass Spectrometry (GD-MS) laboratories to correct the impurity effects using the sum of individual estimates (SIE) method. Comparisons were made between the difference in the realized freezing temperatures and the three differences in the SIE corrections based on the individual assay results. Among them, the impurity compositions analyzed at one laboratory resulted in the difference in the SIE corrections matching the measured temperature difference; that is, the SIE-corrected zinc freezing temperatures based on only one assay laboratory coincided with the measurement result. Therefore, the best approximation to the freezing temperature of ideally pure zinc was attained with the aid of the consistent assay result, and the physical measurement of the difference in the realized freezing temperatures could be used as a practical method verifying the consistency and the reliability of the chemical assay results. [ABSTRACT FROM AUTHOR]

Uranium dioxide (UO2) is the standard fuel in light water, nuclear reactors, and its material properties, such as thermal conductivity, bear a great influence on the heat transfer efficiencies of the system. Laser flash analysis is the most common technique employed to measure the thermal properties of bulk UO2 in post-irradiation examination, but there is interest in expanding measurement capabilities to situations where laser flash cannot be applied, such as spatial mapping of localized fuel properties. One potential method is Raman thermometry, where Raman spectra are related to the temperature of the material, but the uncertainties associated with relating temperature to UO2 properties should be investigated. This work investigates the potential viability for measurements based on three existing thermometry techniques, termed Raman-based Thermophysical Property Models (RTPMs), by determining their potential uncertainty when applied to UO2. These are time domain transient techniques (which uses a cantilever sample), a two-laser, steady-state technique (which uses a thin film sample), and a frequency domain photothermal reflectance transient technique (which uses a semi-infinite sample). Using experimental data of the UO2 Raman spectra as a function of temperature, a simulated temperature profile is generated. The thermal diffusivity (α) and/or thermal conductivity (k) are calculated by fitting the RTPMs to temperatures calculated from Raman spectra. The parameter sensitivity and uncertainty associated with each technique are calculated. For time domain methods, whose k and α errors range from 0.5 %–1.1 % to 1.7 %–209 %, respectively, it is concluded that time discretization of published spectra limits the accuracy of our proposed analysis method. For the two-laser methods, which exhibit a k error of 7.5 %, it is discovered that radiation cannot be neglected when thin films are sub-micrometer thick. For the frequency domain methods, which show k and α errors of 0.29 % and 6.8 %, respectively, the underlying fitting assumptions tend to produce large errors, except for a limited range of low frequencies that appear to achieve greater accuracy. In addition, a weak Raman peak is observed in UO2, which limits the effectiveness of transient RTPM-based measurements. [ABSTRACT FROM AUTHOR]

Uranium dioxide (UO2) is the standard fuel in light water, nuclear reactors, and its material properties, such as thermal conductivity, bear a great influence on the heat transfer efficiencies of the system. Laser flash analysis is the most common technique employed to measure the thermal properties of bulk UO2 in post-irradiation examination, but there is interest in expanding measurement capabilities to situations where laser flash cannot be applied, such as spatial mapping of localized fuel properties. One potential method is Raman thermometry, where Raman spectra are related to the temperature of the material, but the uncertainties associated with relating temperature to UO2 properties should be investigated. This work investigates the potential viability for measurements based on three existing thermometry techniques, termed Raman-based Thermophysical Property Models (RTPMs), by determining their potential uncertainty when applied to UO2. These are time domain transient techniques (which uses a cantilever sample), a two-laser, steady-state technique (which uses a thin film sample), and a frequency domain photothermal reflectance transient technique (which uses a semi-infinite sample). Using experimental data of the UO2 Raman spectra as a function of temperature, a simulated temperature profile is generated. The thermal diffusivity (α) and/or thermal conductivity (k) are calculated by fitting the RTPMs to temperatures calculated from Raman spectra. The parameter sensitivity and uncertainty associated with each technique are calculated. For time domain methods, whose k and α errors range from 0.5 %–1.1 % to 1.7 %–209 %, respectively, it is concluded that time discretization of published spectra limits the accuracy of our proposed analysis method. For the two-laser methods, which exhibit a k error of 7.5 %, it is discovered that radiation cannot be neglected when thin films are sub-micrometer thick. For the frequency domain methods, which show k and α errors of 0.29 % and 6.8 %, respectively, the underlying fitting assumptions tend to produce large errors, except for a limited range of low frequencies that appear to achieve greater accuracy. In addition, a weak Raman peak is observed in UO2, which limits the effectiveness of transient RTPM-based measurements. [ABSTRACT FROM AUTHOR]

Single-pressure refractive index gas thermometry (SPRIGT) is a new type of primary thermometry, which needs an extremely stable working pressure (stability < 4 ppm). In practice, the pressure control system at room temperature is located above the cold resonator at 5 K to 25 K, and a long pressure tube is used to connect them, which entails a hydrostatic pressure correction (HPC). To this end, a three-dimensional (3D) Computational Fluid Dynamics (CFD) simulation model of the pressure tube has been developed and compared with experimental results. First, to verify the simulation results, the helium-4 gas pressure in the center of the resonator was measured using a determination of the refractive index by microwave resonance coupled with the knowledge of the temperature. Results of simulation and experiment showed good agreement. Thereafter, based on this CFD simulation, the non-linear temperature distribution in the vertical pressure tube and the uncertainty caused by this non-linear phenomenon were calculated. After this, the validity of the isothermal assumption to simplify the calculation of the HPC was verified. Finally, the effect of heating on the pressure was studied and its impact found to be negligible. To the best of our knowledge, this is the first time experimental and simulation results have been compared for the HPC. The results are expected to be more generally applicable to the accurate determination of pressure in cryostats. [ABSTRACT FROM AUTHOR]

A series of metal–carbon (M–C) eutectics with robust reproducible melting phase transitions are evolving as the reference high-temperature fixed-points up to 3000 °C for radiation thermometry. The mise-en-pratique prepared for the realization and dissemination of new kelvin allows the use of set of M-C blackbody fixed-points or a combination of M-C fixed-points along with silver (Ag), gold (Au) or copper (Cu) blackbodies for the direct measurement of thermodynamic temperatures at high-temperature range. The iron–carbon (Fe–C) [1153 °C] and cobalt–carbon (Co–C) [1324 °C] fixed-point cells are the doorway to high temperature above a copper fixed-point. This paper describes the in-house development of Fe–C and Co–C eutectic graphite crucible blackbodies and their realizations by linear spectral pyrometer (LP4, 650 nm) at CSIR-NPL, National Metrology Institute (NMI) of India. The novel design and assembly approaches were employed to fabricate the blackbody crucibles with 120o inner-well cone, 100 mm ingot length and 8 mm aperture diameter with 0.9997 emissivity and robust thermo-mechanical stability. The eutectic ingots were prepared by multiple fillings of the homogeneously ground and mixed powders with 4.2 and 2.6 weight percentage of carbon in Fe and Co, respectively. Repeatability of measured melting plateau and uncertainty of the temperature measurement for both Fe–C and Co–C cells are presented. The ITS-90 temperatures (T90) to these M-C fixed-points were assigned by a spectral radiance ratio measurement (Planck's Law) relative to the freezing point of Ag [961.78 °C]. The T90 temperatures thus determined for Fe–C and Co–C blackbody fixed-point cells are 1154.05 °C and 1323.93 °C with the expanded uncertainty of 0.37 °C and 0.50 °C, respectively. [ABSTRACT FROM AUTHOR]

A difference was determined between temperature defined by International Temperature Scale (ITS-90) and thermodynamic temperature measured by relative acoustic gas thermometry at 79.0000 K and at 83.8058 K. Measurement were carried out using misaligned spherical acoustic resonator filled with helium at different pressures. The isotherms were fitted for four different acoustic modes simultaneously assuming the same thermal accommodation coefficient and third acoustic virial coefficient for all modes. Our measurements yield the following differences between the thermodynamic temperature T and ITS-90 temperature T 90 : T - T 90 = - 4.81 ± 1.02 mK at 83.9058 K and T - T 90 = - 4.47 ± 0.97 mK at 79.0000 K. [ABSTRACT FROM AUTHOR]

The differences, T − T90, between thermodynamic temperature, T, and temperature, T90, on the International Temperature Scale of 1990 (ITS-90) above the Cu fixed-point temperature, 1357.77 K, were investigated using relative primary radiometric thermometry. The Ag and Cu fixed points were used as reference points for temperature realization by the ITS-90 (n = 1) scheme. The values of T − T90 for the Ag and Cu fixed points have been previously determined as 46.2 mK and 52.1 mK, respectively. Extrapolating these differences based on the sensitivity coefficient used to propagate the uncertainty in the fixed-point temperature to other temperatures results in values of T − T90 of 325 mK or 303 mK at 3000 °C when using the Ag or Cu point T − T90 difference, respectively. These values were confirmed by realizing n = 1 temperature scales using either the thermodynamic values or the ITS-90 values of these fixed points as the reference temperatures and comparing the differences on the two scales. Measurements at the Co–C eutectic point indicated the consistency of thermodynamic temperature realization using the n = 1 scheme, and also demonstrated the equivalence of absolute and relative radiometric thermometry. [ABSTRACT FROM AUTHOR]

Herein, progress in the development of an acoustic gas thermometry (AGT) system at the National Metrology Institute of Japan is reported. This AGT system is an initial low-cost version that uses a 1-l quasi-spherical resonator (QSR) made of oxygen-free copper. The system was tested by measuring the speed of sound in argon at the temperature of triple point of water. Measurements were conducted at ten different pressures, ranging from 60 kPa to 420 kPa. The ideal gas limit of the squared speed of sound was obtained through extrapolation, and a preliminary calculation of the Boltzmann constant, which was 12 ppm below the CODATA2014 value, was made. Large inconsistencies among microwave and acoustic modes were observed, which are dominant sources of uncertainty in speed of sound measurements. The system will be improved by replacing the present QSR with another one that is more precisely fabricated. [ABSTRACT FROM AUTHOR]

CETIAT's calibration laboratory, accredited by COFRAC, is a secondary thermometry laboratory. It uses overflow and stirred calibration baths $$(\hbox {from} -\,80\,{^{\circ }}\hbox {C} \hbox { up } \hbox { to } +\,215\,{^{\circ }}\hbox {C})$$ , dry blocks and furnaces $$(\hbox {from } +\,100\,{^{\circ }}\hbox {C} \hbox { up } \hbox { to } +\,1050\,{^{\circ }}\hbox {C})$$ and thermostatic chambers $$(\hbox {from } -\,30\,{^{\circ }}\hbox {C} \hbox { up } \hbox { to } +\,160\,{^{\circ }}\hbox {C})$$ . Typical calibration uncertainties that can be reached for platinum resistance thermometers in a thermostatic bath are between $$0.03\,{^{\circ }}\hbox {C}$$ and $$0.06\,{^{\circ }}\hbox {C}$$ . In order to improve its calibration capabilities, CETIAT is working on the implementation of a gas-controlled heat pipe (GCHP) temperature generator, used for industrial sensor calibrations. This article presents the results obtained during the characterization of water GCHP for industrial applications. This is a new approach to the use of a heat pipe as a temperature generator for industrial sensor calibrations. The objective of this work is to improve measurement uncertainties and daily productivity. Indeed, as has been shown in many studies (Dunn and Reay in Heat Pipes, Pergamon Press, Oxford, 1976; Merlone et al. 2012), the temperature of the system is pressure dependent and the response time, in temperature, follows the pressure accordingly. Thanks to this generator, it is possible to perform faster calibrations with smaller uncertainties. In collaboration with INRiM, the GCHP developed at CETIAT works with water and covers a temperature range from $$+\,30\,{^{\circ }}\hbox {C}$$ up to $$+\,150\,{^{\circ }}\hbox {C}$$ . This device includes some improvements such as a removable cover, which allows us to have different sets of thermometric wells adjustable according to the probe to be calibrated, and a pressure controller based on a temperature sensor. This article presents the metrological characterization in terms of homogeneity and stability in temperature. A rough investigation of the response time of the system is also presented in order to evaluate the time for reaching thermal equilibrium. The results obtained in this study concern stability and thermal homogeneity. The homogeneity on 200 mm is better than 5 mK and with a calibration uncertainty reduced by a factor of three. [ABSTRACT FROM AUTHOR]

Two Co-C and Pd-C eutectic fixed point cells for both radiation thermometry and thermocouple thermometry were constructed at NMC. This paper describes details of the cell design, materials used, and fabrication of the cells. The melting curves of the Co-C and Pd-C cells were measured with a reference radiation thermometer realized in both a single-zone furnace and a three-zone furnace in order to investigate furnace effect. The transition temperatures in terms of ITS-90 were determined to be $$1324.18\,{^{\circ }}\hbox {C}$$ and $$1491.61\,{^{\circ }}\hbox {C}$$ with the corresponding combined standard uncertainty of $$0.44\,{^{\circ }}\hbox {C}$$ and $$0.31\,{^{\circ }}\hbox {C}$$ for Co-C and Pd-C, respectively, taking into account of the differences of two different types of furnaces used. The determined ITS-90 temperatures are also compared with that of INRIM cells obtained using the same reference radiation thermometer and the same furnaces with the same settings during a previous bilateral comparison exercise (Battuello et al. in Int J Thermophys 35:535-546, 2014). The agreements are within $$k=1$$ uncertainty for Co-C cell and $$k = 2$$ uncertainty for Pd-C cell. Shapes of the plateaus of NMC cells and INRIM cells are compared too and furnace effects are analyzed as well. The melting curves of the Co-C and Pd-C cells realized in the single-zone furnace are also measured by a Pt/Pd thermocouple, and the preliminary results are presented as well. [ABSTRACT FROM AUTHOR]

Absolute spectral radiometry is currently the only established primary thermometric method for the temperature range above 1300 K. Up to now, the ongoing improvements of high-temperature fixed points and their formal implementation into an improved temperature scale with the mise en pratique for the definition of the kelvin, rely solely on single-wavelength absolute radiometry traceable to the cryogenic radiometer. Two alternative primary thermometric methods, yielding comparable or possibly even smaller uncertainties, have been proposed in the literature. They use ratios of irradiances to determine the thermodynamic temperature traceable to blackbody radiation and synchrotron radiation. At PTB, a project has been established in cooperation with VNIIOFI to use, for the first time, all three methods simultaneously for the determination of the phase transition temperatures of high-temperature fixed points. For this, a dedicated four-wavelengths ratio filter radiometer was developed. With all three thermometric methods performed independently and in parallel, we aim to compare the potential and practical limitations of all three methods, disclose possibly undetected systematic effects of each method and thereby confirm or improve the previous measurements traceable to the cryogenic radiometer. This will give further and independent confidence in the thermodynamic temperature determination of the high-temperature fixed point's phase transitions. [ABSTRACT FROM AUTHOR]

The evolving mise en pratique for the definition of the kelvin (MeP-K) [1, 2] will, in its forthcoming edition, encourage the realization and dissemination of the thermodynamic temperature either directly (primary thermometry) or indirectly (relative primary thermometry) via fixed points with assigned reference thermodynamic temperatures. In the last years, the Centro Español de Metrología (CEM), in collaboration with the Instituto de Óptica of Consejo Superior de Investigaciones Científicas (IO-CSIC), has developed several setups for absolute calibration of standard radiation thermometers using the radiance method to allow CEM the direct dissemination of the thermodynamic temperature and the assignment of the thermodynamic temperatures to several fixed points. Different calibration facilities based on a monochromator and/or a laser and an integrating sphere have been developed to calibrate CEM's standard radiation thermometers (KE-LP2 and KE-LP4) and filter radiometer (FIRA2). This system is based on the one described in [3] placed in IO-CSIC. Different light sources have been tried and tested for measuring absolute spectral radiance responsivity: a Xe-Hg 500 W lamp, a supercontinuum laser NKT SuperK-EXR20 and a diode laser emitting at 6473 nm with a typical maximum power of 120 mW. Their advantages and disadvantages have been studied such as sensitivity to interferences generated by the laser inside the filter, flux stability generated by the radiant sources and so forth. This paper describes the setups used, the uncertainty budgets and the results obtained for the absolute temperatures of Cu, Co-C, Pt-C and Re-C fixed points, measured with the three thermometers with central wavelengths around 650 nm. [ABSTRACT FROM AUTHOR]

A new European project called EMPRESS, funded by the EURAMET program 'European Metrology Program for Innovation and Research,' is described. The 3 year project, which started in the summer of 2015, is intended to substantially augment the efficiency of high-value manufacturing processes by improving temperature measurement techniques at the point of use. The project consortium has 18 partners and 5 external collaborators, from the metrology sector, high-value manufacturing, sensor manufacturing, and academia. Accurate control of temperature is key to ensuring process efficiency and product consistency and is often not achieved to the level required for modern processes. Enhanced efficiency of processes may take several forms including reduced product rejection/waste; improved energy efficiency; increased intervals between sensor recalibration/maintenance; and increased sensor reliability, i.e., reduced amount of operator intervention. Traceability of temperature measurements to the International Temperature Scale of 1990 (ITS-90) is a critical factor in establishing low measurement uncertainty and reproducible, consistent process control. Introducing such traceability in situ (i.e., within the industrial process) is a theme running through this project. [ABSTRACT FROM AUTHOR]

Metal carbon eutectic cells (high-temperature fixed points, HTFPs) (Machin in AIP Conf Proc 1552:305, 2013) are being considered for use as reliable high-temperature references for non-contact thermometry above the copper point ( $$1084.62\,^{\circ }\hbox {C}$$ ). Recent studies have demonstrated the concept of using doped metal carbon eutectic cells as artefacts suitable for temperature scale comparisons (Teixeira et al. in AIP Conf Proc 1552:363, 2013; Teixeira et al. in Int J Thermophys 35:467-474, 2014; Machin et al. in Int J Thermophys 36:327-335, 2015). When using such artefacts, the participating institutes do not know the realization temperature of the doped HTFP cell, because it has been modified by the addition of a selected dopant at a definite concentration. The use of such fixed points can critically evaluate the real measurement capability of the institutes in any comparison. The pyrometry laboratory of Inmetro developed a set of doped Ni-C eutectic cells in 2012 and 2013. This paper describes the long-term stability of a Sn-doped Ni-C cell constructed in 2012, which accumulated more than 220 h above $$1300\,^{\circ }\hbox {C}$$ amounting to more than 50 cycles of melts and freezes. The cell remained stable, well within the measurement uncertainty, throughout the evaluation period demonstrating the utility of such cells for scale comparison purposes. [ABSTRACT FROM AUTHOR]

Previously, the authors have published work describing a pure Ni fixed point within alumina crucibles. The success of this study stimulated working with the Ni-Ag monotectic point in alumina crucibles. Similar to eutectic points, the Ni-Ag monotectic temperature is an invariant point but it differs from a eutectic reaction in such a way that the monotectic phase change takes place from Ni-Ag liquid solution to Ni-Ag solid solution and Ag rich Ni-Ag liquid solution. In the phase diagram references, the Ni-Ag monotectic phase transition temperature is assigned to be about 20 $$^{\circ }$$ C below the pure Ni melting/freezing point. As is the case for pure Ni, mechanical stability is one of the concerns. Therefore, proper cell design is necessary to avoid breakage of the alumina crucible. The techniques used for the fabrication and measurement of the pure Ni cell were applied to the Ni-Ag cell as well. The cells have been successfully fabricated and the temperature measurement at the fixed point was carried out for more than 20 thermal cycles in total. A Pt/Pd thermocouple was used to measure the temperature and was calibrated from the tin point to the gold point to measure the ITS-90. Freezing plateaus are realized with the technique of 'recurrent offset freezing method with reserved solid'. The duration of each freezing plateau is a minimum of 30 min. The monotectic transformation temperature for the best performed cell is determined as 1428.27 $$^{\circ }$$ C with a combined uncertainty of ±0.06 $$^{\circ }$$ C ( $${k}=1$$ ). [ABSTRACT FROM AUTHOR]

The calibration of Pt/Rh thermocouples up to 1560 $$^{\circ }\hbox {C}$$ at NMIA currently uses the conventional 'melt-wire technique' to realize Gold (Au) and Palladium (Pd) melting points, resulting in the loss of 20 mm of wire from the junction end for each calibration. To avoid this loss, NMIA intends to replace the melt-wire technique with the use of miniature fixed-point cells. NMIA has established Copper (Cu) and Cobalt-Carbon (Co-C) eutectic cells for calibration of thermocouples to 1324 $$^{\circ }\hbox {C}$$ . To extend the calibration up to 1500 $$^{\circ }\hbox {C}$$ , miniature Palladium-Carbon (Pd-C) eutectic cells (1492 $$^{\circ }\hbox {C}$$ ) have been constructed and tested in collaboration with NMIJ, AIST. Although these cells are made of high-purity reference materials, careful consideration must be given to contamination introduced during the manufacture and filling of the crucibles and by their long-term use. These issues can only be assessed by measurement of cell-to-cell temperature differences within the ensemble of cells traceable to ITS-90. In the work presented here, 3 NMIA-design mini Pd-C cells were constructed: 1 at NMIA and 2 at NMIJ. These cells were compared, together with a 'large' NMIJ Pd-C cell, using type-R, type-B and Pt/Pd thermocouples and radiation thermometry. Although the cells are found to be stable and repeatable, significant problems arising from migration of Pd to the thermocouples were identified. [ABSTRACT FROM AUTHOR]

In this paper, we report on the development at NRC of a sulfur hexafluoride ( $$\text {SF}_6$$ ) fixed-point cell for calibrating long-stem standard platinum resistance thermometers. Discussed in detail are the unique challenges of constructing the high-pressure fixed-point cell and realizing the triple point of $$\text {SF}_6$$ in a commercial stirred liquid bath. [ABSTRACT FROM AUTHOR]

Recent advances in primary acoustic gas thermometry (AGT) have revealed significant differences between temperature measurements using the International Temperature Scale of 1990, $$T_{90}$$ , and thermodynamic temperature, T. In 2015, we published estimates of the differences $$(T-T_{90})$$ from 118 K to 303 K, which showed interesting behavior in the region around the triple point of water, $$T_\mathrm{TPW}=273.16$$ K. In that work, the $$T_{90}$$ measurements below $$T_\mathrm{TPW}$$ used a different ensemble of capsule standard platinum resistance thermometers (SPRTs) than the $$T_{90}$$ measurements above $$T_\mathrm{TPW}$$ . In this work, we extend our earlier measurements using the same ensemble of SPRTs above and below $$T_\mathrm{TPW}$$ , enabling a deeper analysis of the slope $$\mathrm{d}(T-T_{90})/\mathrm{d}T$$ around $$T_\mathrm{TPW}$$ . In this article, we present the results of seven AGT isotherms in the temperature range 258 K to 323 K. The derived values of $$(T-T_{90})$$ have exceptionally low uncertainties and are in good agreement with our previous data and other AGT results. We present the values $$(T-T_{90})$$ alongside our previous estimates, with the resistance ratios W( T) from two SPRTs which have been used across the full range 118 K to 323 K. Additionally, our measurements show discontinuities in $$\mathrm{d}(T-T_{90})/\mathrm{d}T$$ at $$T_\mathrm{TPW}$$ which are consistent with the slope discontinuity in the SPRT deviation functions. Since this discontinuity is by definition non-unique, and can take a range of values including zero, we suggest that mathematical representations of $$(T-T_{90})$$ , such as those in the mise en pratique for the kelvin (Fellmuth et al. in Philos Trans R Soc A 374:20150037, 2016. doi:), should have continuity of $$\mathrm{d}(T-T_{90})/\mathrm{d}T$$ at $$T_\mathrm{TPW}$$ . [ABSTRACT FROM AUTHOR]

The use of a $$\hbox {RuO}_{2}$$ resistor in non-isothermal measuring setup is proposed. A calculation is presented to explain the principle for a resistor obeying variable-range-hopping theory and the results are compared to measurements in the range of 11.2-30 mK for a commercial resistor. The thermometer, which measures the electron temperature, does not show overheating effects at 11.2 mK with a measuring power of $$10^{-12}$$ W. [ABSTRACT FROM AUTHOR]

For a number of applications in control and safety value monitoring, a profound knowledge of the dynamic behavior of process temperature sensors is of great importance. Sensor test procedures and model identification methods are state of the art for small temperature changes, i.e., steps. For wider temperature ranges, the temperature dependency of the material characteristics is significant, too. The resulting non-linearities limit the utilization of classical model concepts. In this paper, we introduce and solve a non-linear ordinary differential equation for the linear dependency of the material characteristic parameters, i.e., for the basic case of non-constant material parameters. The analytic solution will be explained, and the results are discussed and compared to a finite element method model of a basic cylinder. [ABSTRACT FROM AUTHOR]

Application of radiation thermometry in industrial scenes is rapidly increasing with the widespread use of low-cost infrared thermometers and thermal imagers. However, their performances are not always up to the users' expectations. This is often due to lack of appropriate information on the limitations of the instrument performance and of radiation thermometry itself. In this article, these limitations are disclosed, namely the targeting capabilities of the thermometers including the size-of-source effect of thermal imagers, reflection errors, and unknown emissivity of the measurement object. Attempts made at the NMIJ are introduced, which aim at alleviating the effect of these difficulties. Two-color radiation thermometers have been neglected from the traceability chain and from standardization efforts due to their technical complexity. Recent activities to incorporate them effectively in the calibration chain and to establish international standards are presented. Calibration of low-cost thermometers with a fixed instrumental emissivity setting has been an issue for calibration laboratories. Simple apparatus that enables calibration of such instruments is described. Methods to compensate for unknown emissivities are presented utilizing auxiliary sources to realize a blackbody condition, which is applied to thermal imagers to overcome the problem of the size-of-source effect and reflection error at the same time. Extensions of the technique to objects with specular and scattering surfaces are described. Such efforts are encouraged in the thermometry community since they are essential in establishing an unbroken chain of traceability to the industrial front. [ABSTRACT FROM AUTHOR]

The worldwide history and present state of development of rhodium-iron resistance thermometers (RIRTs) is briefly reviewed. A standardized interpolation method using RIRTs with the nominal composition of 0.5 % Fe (by mole) is presented, with examples using data taken from 60 RIRTs made from a variety of wire batches and sources worldwide over the last 40 years. The parameterization exploits the favorable characteristics of the Cragoe reduced resistance $$Z(\tau )$$ and a suitably reduced temperature $$\tau $$ . A reference function $$Z_\mathrm{ref}(\tau )$$ which approximates the average characteristics of selected wire is derived for use over the interval 0.65 K to 24.5561 K on the ITS-90. The deviations of real RIRT data from this reference function are examined, and simple four-parameter Fourier-series solutions for the resulting deviation curves are presented. Despite the fact that the wire samples may be of different origins or state-of-anneal, it was found that the interpolations are successful for most of the samples studied over the 4.2 K to 24.5561 K interval, at the level of $$\approx $$ 1 $$\hbox {mK}$$ standard uncertainty or less. This method would allow for calibrations of most RIRTs over this interval using only six calibration points, permitting an efficiency not achievable using the common least-squares curve-fitting calibration methods. The potential of this formalism for a standardized interpolation scheme using RIRTs is discussed. [ABSTRACT FROM AUTHOR]

A roadmap for thermophysical properties metrology was developed in spring 2011 by the Thermophysical Properties Working Group in the EURAMET Technical Committee in charge of Thermometry, Humidity and Moisture, and Thermophysical Properties metrology. This roadmapping process is part of the EURAMET (European Association of National Metrology Institutes) activities aiming to increase impact from national investment in European metrology R&D. The roadmap shows a shared vision of how the development of thermophysical properties metrology should be oriented over the next 15 years to meet future social and economic needs. Since thermophysical properties metrology is a very broad and varied field, the authors have limited this roadmap to the following families of properties: thermal transport properties (thermal conductivity, thermal diffusivity, etc.), radiative properties (emissivity, absorbance, reflectance, and transmittance), caloric quantities (specific heat, enthalpy, etc.), thermodynamic properties (PVT and phase equilibria properties), and temperature-dependent quantities (thermal expansion, compressibility, etc.). This roadmap identifies the main societal and economical triggers that drive developments in thermophysical properties metrology. The key topics considered are energy, environment, advanced manufacturing and processing, public safety, security, and health. Key targets that require improved thermophysical properties measurements are identified in order to address these triggers. Ways are also proposed for defining the necessary skills and the main useful means to be implemented. These proposals will have to be revised as needs and technologies evolve in the future. [ABSTRACT FROM AUTHOR]

In principle, multiwavelength radiation thermometry allows one to correctly measure the temperature of surfaces of unknown and varying surface emissivity. Unfortunately, none of the practical realizations proposed in the past proved to be sufficiently reliable because of a strong influence of the errors arising from incorrect modeling of the emissivity and of the limited number of operating wavelengths. The use of array detectors allows a high degree of flexibility both in terms of number and spectral position of the working wavelength bands. In the case of applications at high temperatures, i.e., near 2000 $$^{\circ }$$ C or above, an analysis of the theoretical measuring principles of multiwavelength thermometry, suggests the opportunity of investigating the possible advantages in extending the operating wavelengths toward the ultraviolet region. To this purpose, a simulation program was developed which allows investigation of the effect of different influencing parameters. This paper presents a brief theoretical introduction and practical analysis of the method. The best choices are derived in terms of the different influencing parameters and data relative to the simulation of both real materials and fictitious emissivity curves and have been studied and analyzed with different emissivity models to check the robustness of the method. [ABSTRACT FROM AUTHOR]

At the National Metrology Institute of Japan (NMIJ), the triple points of $$^{20}$$ Ne and $$^{22}$$ Ne were realized using modular sealed cells, manufactured by the Istituto Nazionale di Ricerca Metrologica (INRiM) in Italy to measure the difference of the triple-point temperatures of $$^{20}$$ Ne and $$^{22}$$ Ne. Standard platinum resistance thermometers (SPRTs) were used that were calibrated by NMIJ on the International Temperature Scale of 1990 (ITS-90). In previous reports, sealed cells of $$^{20}$$ Ne and $$^{22}$$ Ne were mounted one at a time in a cryostat and their triple points were realized in separate cool-downs (the single-cell measurement). In this study, first, the triple point was realized using the single-cell measurement for $$^{20}$$ Ne and $$^{22}$$ Ne cells. Second, the $$^{20}$$ Ne and $$^{22}$$ Ne cells were mounted together on the same copper block and their triple points were realized subsequently one after the other in the same cool-down of the cryostat (the double-cell measurement). The melting curves observed by the single-cell and the double-cell measurements were almost identical for each cell. The difference of the triple-point temperatures between the two cells, $$^{22}T -^{20}\!T$$ , was estimated, not only using the subrange of SPRTs defined in the ITS-90 from 13.8033 K to 273.16 K (subrange 1) but also that defined from 24.5561 K to 273.16 K (subrange 2). The difference in $$(^{22}T-^{20}\!\!T)$$ between the subranges 1 and 2 is within 0.06 mK, which is caused by the subrange inconsistency in the ITS-90. The standard uncertainty in $$(^{22}T-^{20}\!T)$$ due to the subrange inconsistency is estimated to be 0.017 mK. After correction for the effects of impurities and other isotopes in the $$^{20}$$ Ne and $$^{22}$$ Ne cells, the difference in the triple-point temperatures between pure $$^{20}$$ Ne and pure $$^{22}$$ Ne is estimated to be 0.146 64 (5) K on subrange 1, which is consistent within the uncertainty with the former studies. When $$^{22}T-^{20}\!T$$ for pure $$^{20}$$ Ne and pure $$^{22}$$ Ne is estimated on subrange 2, $$^{22}T-^{20}\!\!T$$ becomes 0.146 60 (5), which agrees very well with the former reports of INRiM evaluating $$^{22}T-^{20}\!T$$ on subrange 2. [ABSTRACT FROM AUTHOR]

This study explores the design and construction of an ultra-low temperature facility in order to realize the Provisional low-temperature scale from 0.9 mK to 1 K (PLTS-2000) in Japan, to disseminate its use through calibration services, and to study thermometry at low temperatures below 1 K. To this end, a dilution refrigerator was constructed in-house that has four sintered silver discrete heat exchangers for use as a precooling stage of a copper nuclear demagnetization stage. A $$^{3}\text {He}$$ melting curve thermometer attached to the mixing chamber flange could be cooled continuously to 4.0 mK using the refrigerator. The dependence of minimum temperatures on circulation rates can be explained by the calculation of Frossati's formula based on a perfect continuous counterflow heat exchanger model, assuming that the Kapitza resistance has a $$T^{-3}$$ temperature dependence. Residual heat leakage to the mixing chamber was estimated to be around 86 nW. A nuclear demagnetization cryostat with a nuclear stage containing an effective amount of copper (51 mol in a 9 T magnetic field) is under construction, and we will presently start to work toward the realization of the PLTS-2000. In this article, the design and performance of the dilution refrigerator are reported. [ABSTRACT FROM AUTHOR]

The use of melting or freezing temperatures of high-purity substances as thermometric fixed points requires a knowledge of the binary phase diagrams of these substances and remaining impurities at very small impurity concentrations. In this paper, a calorimetric apparatus for the measurement of the change in liquidus temperature of fixed-point metals due to dissolved impurities at quasi-adiabatic conditions is presented. This approach combines advantages of the fixed-point method and adiabatic calorimetry. It is more efficient for the screening of a range of impurity concentrations than a fixed-point cell, requires less constructional and experimental expenditure compared with an adiabatic calorimeter, but provides similar small uncertainties on the millikelvin level. Measurements were carried out to determine the influence of lead on the melting temperature of indium at mass fractions up to 6.93 %. The results are in very good agreement with previous measurements by means of slim fixed-point cells in the Physikalisch-Technische Bundesanstalt and confirm a minimum of the freezing point of $$-$$ 178 mK at a mass fraction of about 3.7 %. It was demonstrated that this setup allows the investigation of binary phase diagrams with uncertainties less than 8 mK. [ABSTRACT FROM AUTHOR]

As the initial process in an integrated steel-making plant, molten iron is produced in a blast furnace. The molten iron has a temperature between 1700 K and 1900 K. The outflow stream discharged from a taphole comprises the molten iron and slag (which is a mixture of molten oxides). Monitoring of the stream temperature is important because it has information on the thermal condition inside the blast furnace. A newly developed simultaneous measurement technique for temperature and iron-slag ratio is reported. A monochromatic CCD camera with a short exposure time is used to obtain a thermal image of the rapidly moving stream. The thermal image has a marble-like pattern caused by the physical separation of the iron and slag and their different optical properties. Iron thermometry is realized by automatically detecting the peak of the iron gray-level distribution on a histogram. Meanwhile, the thermal radiance of the semitransparent slag varies as a function of the thickness. The slag temperature is calculated from the maximum gray level, presuming that the emissivity of the slag is constant at a thick slag part. The slag ratio is measured by counting the number of pixels on the histogram. A field test was carried out at an operating blast furnace. The iron temperature, slag temperature, and slag ratio were successfully measured. This multiple image measurement is expected to be the new information source for stable blast furnace operation. [ABSTRACT FROM AUTHOR]

Acoustic gas thermometry relies on the fundamental relationship between the speed of sound in a monatomic gas and its thermodynamic temperature. The speed of sound is calculated from the resonance frequencies of a cavity whose dimensions or thermal expansivity must be measured with high accuracy. For quasi-spherical cavities, the use of microwave resonances is a successful and proven dimensional measurement technique. The simplicity and economy of cylindrical resonators makes them an attractive alternative to quasi-spherical resonators, particularly for high-temperature thermometry. This article summarizes the basic theory of cylindrical microwave resonators, and describes methods for obtaining cavity dimensions from the mode frequencies. The perturbing effects of cavity shape deformations, the wall to end-plate junction, coupling probes and non-conducting surface layers are discussed. The results of an experiment with a simple aluminum cavity are presented, which demonstrate the superior performance of the TE0 $$pq$$ modes over the more commonly used TM0 $$pq$$ modes. [ABSTRACT FROM AUTHOR]

A robust fixed point using pure nickel contained in an alumina crucible has been developed for thermocouple calibrations. It was observed that a deep supercool often caused the freezing plateau to be short and have a large slope. A procedure for realizing the pure nickel fixed points was developed that reserved a small amount of nickel in the solid state to act as a seed for nucleation of the freeze. This procedure was found to allow freezing plateaus that were suitably long and flat to make them useful for calibrating thermocouples. Using a calibrated Pt/Pd thermocouple, the freezing temperature of nickel was determined to be $$1455.22\,^{\circ }\hbox {C}$$ with a $$(k = 2)$$ uncertainty of $$0.8\,^{\circ }\hbox {C}$$ . [ABSTRACT FROM AUTHOR]

In recent years, numerical modeling of heat transfer in fixed-point cells has become a useful tool for the investigation of various thermal effects, leading to optimized measurement setups and procedures, as well as more realistic uncertainty estimations. Although numerical modeling of heat transfer is commonly used in many scientific and industrial projects, its application in primary thermometry presents several challenges. Besides the required high accuracy, the major challenge is the correct implementation of radiative heat transfer, which must take into account effects such as reflection, refraction, scattering, emission, absorption, etc. Correct modeling of thermal radiation is especially important for temperatures above $$400\,^{\circ }\hbox {C}$$ , where thermal radiation becomes the dominant mode of heat transfer. In this paper, the results of modeling with a custom-made numerical model are presented. The model is based on the finite difference method and calculates the steady-state solution in 2D cylindrical coordinates with axial symmetry. Radiation is modeled using the discrete ordinates method, which calculates the radiation intensity in every point in a specified number of fixed directions. Computation of the radiation intensity is extremely computationally demanding, but it provides a way of accurately handling all radiation-related thermal effects. The input data for the model geometrical properties are provided in a form of a bitmap image, which enables simple adjustment for different model configurations. Special emphasis is given to accurate modeling of total internal reflection in a glass assembly, which results in a light-piping effect. Reduction of this effect by sandblasting of glass surfaces is investigated. [ABSTRACT FROM AUTHOR]

Thermal modeling is used for thermal investigation and optimization of sensors, instruments, and structures. Here, results depend on the chosen modeling approach, the complexity of the model, the quality of material data, and the information about the heat transport conditions of the object of investigation. Despite the widespread application, the advantages and limits of the modeling approaches are partially unknown. For comparison of different modeling approaches, a simplified and analytically describable demonstration object is used. This object is a steel rod at well-defined heat exchange conditions with the environment. For this, analytically describable models, equivalent electrical circuits, and simple and complex finite-element-analysis models are presented. Using the different approaches, static and dynamic simulations are performed and temperatures and temperature fields in the rod are estimated. The results of those calculations, comparisons with measurements, and identification of the sensitive points of the approaches are shown. General conclusions for thermal modeling of complex equipment are drawn. [ABSTRACT FROM AUTHOR]

A series of high-temperature fixed points (HTFPs) Pt-C (1738 $$^{\circ }\mathrm {C}), \text {Cr}_{7}\text {C}_{3}{-\text {Cr}}_{3}\text {C}_{2}\,(1742\,^{\circ } \mathrm{C}), \text {Cr}_{3}\text {C}_{2}{-\text {C}}\,(1826\,^{\circ }\mathrm{C})$$ , and Ru-C (1953 $$^{\circ }\text {C}$$ ) have been constructed at the National Physical Laboratory (NPL) and the Laboratoire National de métrologie et d'Essais and Conservatoire national des arts et métiers (LNE-Cnam). These are required for the calibration of high-temperature thermocouples in the framework of work package 6 of the European Metrology Research Programme IND01 project 'HiTeMS.' The goal of this work package is to establish a European capability that can determine low-uncertainty reference functions of non-standard high-temperature thermocouples. For reference functions to be widely applicable, measurements must be performed by more than one institute and preferably by more than one method. Due to the high price of the ingot materials, miniature HTFP cells are used. NPL and LNE-Cnam constructed their HTFP cells with different designs; these are described here, together with the performance of the cells using both radiation thermometry and thermocouples. The melting temperature of the Ru-C cells (for thermocouple calibrations) was determined using radiation thermometry at both NPL and LNE-Cnam, and the two results are compared. The suitability of the cells for calibration of W-Re and Rh-Ir thermocouples is evaluated, and some results are presented. Some discussion is given regarding the materials challenges when calibrating Rh-Ir thermocouples up to 2000 $$^{\circ }$$ C. [ABSTRACT FROM AUTHOR]

A detailed analysis of the double-wavelength radiation thermometry technique for determining the thermodynamic temperature is presented. This technique provides an alternative method to absolute filter radiometry without the requirement of traceability to the watt. The analysis derives an algebraic expression for the uncertainties in the temperatures measured with the double-wavelength technique, which shows that the optimum strategy is to employ one narrowband and one broadband spectral responsivity, and that the center wavelengths do not need to be widely separated. With current best estimates for signal and spectral responsivity measurements, it is shown that the double-wavelength method can achieve total uncertainties only about four times larger than the current best absolute radiometric methods. Improvements in the signal measurement in the future could possibly reduce the total uncertainty to a level comparable to absolute radiometry. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A technical roadmap for thermometry has been constructed by the EURAMET Technical Committee for Thermometry (TC-T). The roadmap first identified the key triggers that need to be addressed; these included societal grand challenges and the essential scientific metrology to ensure the continued fitness and relevance of the SI unit, the kelvin. In addition, triggers focusing on innovation to support industrial competitiveness such as improvement in product quality and energy efficiency were considered. Clear targets to help address the triggers were formulated; these in turn provide direction to the required temperature measurement research until 2025 and beyond. Although constructed by EURAMET TC-T, the identified societal grand challenges are common within all metrology regions; hence, the roadmap has wider applicability beyond the EURAMET region. A roadmap only ever captures current thinking at the time of formulation, and hence, as with all roadmaps, requires regular revision. For this roadmap this revision will be performed around 2016. This exercise identified that significant research and development were required by the thermometry community if it is to contribute to meet the grand challenges faced by society. The research areas identified here will inform and guide the direction of thermometry research of the national measurement institutes in the EURAMET region over the next decade. [ABSTRACT FROM AUTHOR]

Assessment of thermal immersion effects in the melting and freezing points defined by the International Temperature Scale of 1990 is one of the vital issues of modern thermometry. In documents of the Consultative Committee for Thermometry, the deviation of the experimental immersion profile from the theoretical value of the hydrostatic effect at a height of about 3 cm to 5 cm from the thermometer well bottom is used for the estimation of the uncertainty due to unwanted thermal effects. This estimation assumes the occurrence of solely the hydrostatic effect all along the height of the well inner wall. Real distortions of the temperature gradient at the bottom and at the top part of the well caused by the change of heat-exchange conditions are not taken into account. To define more precisely the temperature gradient along the height of the well, a miniature PRT with a 30 mm sensitive element and a sheath length and diameter of about 60 mm and 6 mm, respectively, were used. Also, the measurements of fixed-points temperature at noticeably different slopes of immersion profiles due to variations of the thermometer heat exchange and phase transition realization conditions were produced by means of a standard platinum resistance thermometer (SPRT). The measurements were carried out at the tin and zinc freezing points. The immersion curves measured with a miniature thermometer demonstrated an increase of the temperature during its lifting in the first 1 cm to 3 cm above the bottom of the well. The measurement results at the zinc freezing point by means of the SPRT have not confirmed the correlation between the immersion curves, the received value of the Zn freezing temperature, and the estimation of its uncertainty. [ABSTRACT FROM AUTHOR]

At PTB new dielectric-constant gas thermometry (DCGT) measurements were performed at the temperature of the triple point of water. As discussed recently in an accompanying paper, the main goal was the determination of the Boltzmann constant $$k$$ as a contribution to the international efforts directed to a new definition of the base unit kelvin via fixing the value of $$k$$ . Besides the linear term in the series expansion used for fitting the results of measurements of DCGT isotherms that reveals $$k$$ , in this paper the higher-order terms are analyzed. For retrieving highly accurate virial coefficients of helium from the data obtained at gas pressures up to 7 MPa, an extended DCGT working equation is developed. Applying this equation, information is deduced on the viral coefficients up to the fourth density virial coefficient. Finally, comparisons with the latest ab initio calculations for the second and third density virial coefficients as well as the second dielectric virial coefficient are performed. [ABSTRACT FROM AUTHOR]

Temperature drift is one of the most significant sources of uncertainty in the calibration of thermometers by comparison. Measuring the resistances, $$R_{1}$$ , etc., by ratio to the resistance of a (similar) reference thermometer, $$R_\mathrm{ref}$$ , rather than to a fixed standard resistor, $$R_{\mathrm{s}}$$ , allows the effect of drift to be overcome. The ratios, $$R_{1}/R_\mathrm{ref}$$ , etc., represent 'instantaneous comparisons' of the two thermometers. They are practically independent of temperature, so the exact temperature of the comparison (and the actual value of $$R_\mathrm{ref}$$ itself) is not of first importance. The key points are that the $$R_{1}/R_\mathrm{ref}$$ , etc. are measured accurately, and that $$R_\mathrm{ref}$$ is accurately related to temperature. This paper describes the method and gives results of its application to the comparison of standard platinum resistance thermometers in liquid nitrogen and liquid argon, with repeatabilities of less than or about 0.1 mK. The method is not new, but it appears not to have been widely used or discussed in the literature. It has potential for application in all comparisons of like thermometers, in liquid baths, metal blocks, and furnaces, as well as in testing the temperature uniformity of the baths, etc., and investigations such as into thermometer stability or hysteresis. Some comparisons in conditions of rapid drift, where thermometer response times become important, are also presented. [ABSTRACT FROM AUTHOR]

Over the medium temperature range (from $$156\,^{\circ }\mathrm{C}$$ to $$1000\,^{\circ }\mathrm{C}$$ ), radiation thermometry is usually established within a national metrology institute (NMI) by means of variable temperature blackbody radiation sources, whose temperature is determined using a platinum resistance thermometer or thermocouple, calibrated in terms of the International Temperature Scale of 1990 (ITS-90), positioned in close proximity to the back radiating surface of the blackbody. It is also reasonably common to establish a scale using a suitable radiation thermometer, such as an indium gallium arsenide (InGaAs) detector-based narrow band radiation thermometer, calibrated using a number of fixed-point blackbody sources from the indium (In) to silver (Ag) (or copper (Cu)) points, with the calibration results fitted using a parameterized Planckian interpolation function. During 2007 and 2008, two InGaAs-based radiation thermometers were circulated around seven NMIs within the European Association of National Metrology Institutes (EURAMET) region in order to undertake a comparison of parameters necessary for radiation thermometry over the medium temperature range. Measurements were made of the size-of-source effect and gain (range) ratios of the two thermometers along with an assessment of the effect of changes in the ambient temperature and humidity on the thermometer output. The thermometers were also calibrated using fixed-point and/or variable temperature blackbody sources at each institute. A brief overview of the results obtained by this project is presented in this paper. [ABSTRACT FROM AUTHOR]

The first international pilot study of thermal-diffusivity measurements using the laser flash (LF) method was organized by the working group 9 (WG9) of the Consultative Committee for Thermometry (CCT) of the Bureau International des Poids et Mesures (BIPM). Four National Metrology Institutes (NMIs) participated in this comparison. Thermal-diffusivity measurements on the Armco iron and the isotropic graphite IG-110 were carried out from room temperature to about 1200 K. The sample sets consist of five disk-shaped specimens of 10 mm in diameter and (1.0, 1.4, 2.0, 2.8, and 4.0) mm in thickness, each cut from the same block of material. These sample sets were specifically prepared for the comparison and sent to the participants. In the pilot comparison, the thermal diffusivity of each sample was estimated using the LF method with a specific extrapolating procedure. This procedure has the advantage of determining the inherent thermal diffusivity of the material. The extrapolated value in a plot of measured apparent thermal-diffusivity values versus the amplitude of the output signal corresponding to the temperature rise during each measurement is defined as the inherent thermal diffusivity. The overall results showed good agreement between independent laboratories, measurement equipment, and specimen thicknesses. The thermal diffusivities of the materials were determined using our measured results. A quantitative evaluation of the variability of the data obtained by the participants has been done, by evaluating the deviations from the reference value, the Z-value, and the En-number. Some data showed a large deviation from the reference value. It was concluded that these are caused by an insufficient time response of the measurement equipment and some difficulties with changing the pulsed heating energy. The effect of the thermal expansion on the thermal diffusivity was checked. It was found that the thermal-expansion effect was very small and negligible in this case. [ABSTRACT FROM AUTHOR]

The national temperature standard for the low-temperature range between 13.8033 K and 273.16 K has been established in Poland at the Institute of Low Temperature and Structure Research (INTiBS). The standard consists of sealed cells for realization of six fixed points of the International Temperature Scale of 1990 (ITS-90) in the low-temperature range, an adiabatic cryostat and Isotech water and mercury triple-point baths, capsule standard resistance thermometers (CSPRT), and AC and DC bridges with standard resistors for thermometers resistance measurements. INTiBS calibrates CSPRTs at the low-temperature fixed points with uncertainties less than 1 mK. In lower temperature range-between 2.5 K and about 25 K - rhodium-iron (RhFe) resistance thermometers are calibrated by comparison with a standard which participated in the EURAMET.T-K1.1 comparison. INTiBS offers a calibration service for industrial platinum resistance thermometers and for digital thermometers between 77 K and 273 K. These types of thermometers may be calibrated at INTiBS also in a higher temperature range up to 550°C. The Laboratory of Temperature Standard at INTiBS acquired an accreditation from the Polish Centre for Accreditation. A management system according to EN ISO/IEC 17025:2005 was established at the Laboratory and presented on EURAMET QSM Forum. [ABSTRACT FROM AUTHOR]

There is currently great interest in the international metrological community for new accurate determinations of the Boltzmann constant k, with the prospect of a new definition of the unit of thermodynamic temperature, the kelvin. In fact, k relates the unit of energy (the joule) to the unit of the thermodynamic temperature (the kelvin). One of the most accurate ways to access the value of the Boltzmann constant is from measurements of the velocity of the sound in a noble gas. In the method described here, the experimental determination has been performed in a closed quasi-spherical cavity. To improve the accuracy, all the parameters in the experiment (purity of the gas, static pressure, temperature, exact shape of the cavity monitored by EM microwaves, etc.) have to be carefully controlled. Correction terms have been computed using carefully validated theoretical models, and applied to the acoustic and microwave signals. We report on two sets of isothermal acoustic measurements yielding the value k = 1.380 647 74(171) × 10 J · K with a relative standard uncertainty of 1.24 parts in 10. This value lies 1.9 parts in 10 below the 2006 CODATA value (Mohr et al., Rev. Mod. Phys. 80, 633 ()), but, according to the uncertainties, remains consistent with it. [ABSTRACT FROM AUTHOR]

Impurities are a major source of uncertainty in the temperature of a thermometry metal fixed point (of the order of 1 mK). A better understanding of the impurity effect is required to improve top-level metrological thermometry. This investigation reports on some unusual effects of antimony doped into a high-purity (99.9999%) tin sample. The change in temperature and shape of the melting and freezing curves of the tin, caused by low concentrations of the Sb dopant, were measured in order to test the interpolation of previous data. Most historical experiments have worked at much higher impurity concentrations-say of the order of 100 ppm-and in arrangements that are not used on a day-to-day basis in a metrology laboratory. These measurements on the tin were done after doping at mass fractions of approximately (1 and 25) parts per million by weight (ppmw) of antimony. Repeated melting and freezing curves, before and after doping, confirmed the reproducibility of the temperature measurements in this tin cell. The freezing temperature of the tin after adding antimony was higher than for 'pure' tin. However, the temperature change was less than expected, being an average (+0.06±0.03) mK · ppmw. Samples from the tin were analyzed by glow discharge mass spectrometry (GD-MS) before and after doping to detect the distribution of all the impurity elements. If the dopant level detected by GD-MS was used, then a value of (0.18 or 0.29) mK · ppmw was calculated (much closer to the value interpolated from earlier works). There was evidence that the thermal history of metal phase transitions can cause considerable segregation of some impurities and that the effects of this segregation can be clearly seen on the shape of the melting curves of tin doped with Sb. (The segregation might be more pronounced as Sb forms a peritectic in tin, i.e., a 'positive' impurity which increase the phase transition temperature). [ABSTRACT FROM AUTHOR]

The operation of the primary Coulomb blockade thermometer (CBT) is based on a measurement of the bias-voltage-dependent conductance of arrays of tunnel junctions between normal metal electrodes. Here, a comparison of a CBT with a high-accuracy realization of the PLTS-2000 in the range from 0.008 K to 0.65 K is reported. An overall agreement of about 1 % was found for temperatures above 0.25 K. For lower temperatures, differences increase because the CBT does not reach full thermal equilibrium with its surroundings. This can be accounted for by numerical calculations based on electron-phonon decoupling. [ABSTRACT FROM AUTHOR]

The LNE-CNAM, in cooperation with the IPN, has recently developed a new cryogen-free adiabatic calorimeter, to realize the International Temperature Scale of 1990 (ITS-90) in the temperature range between 6 K and 84 K. The new calorimeter, cooled by a closed-cycle Gifford-McMahon refrigerator, is equipped with three thermal shields and two separate vacuum chambers, to minimize the effect of parasitic heat fluxes. The inner adiabatic chamber can accommodate either a multi-compartment cell-containing the triple points of hydrogen, neon, oxygen, and argon, to realize the ITS-90 between 14 K and 84 K-or a comparison block for thermometers, the calibration of rhodium-iron (RhFe) thermometers between 6 K and 24 K. The use of a cryogen-free system and a fully computer-controlled measurement chain allow long lasting experiments and good thermal control, resulting in a substantial reduction of the measurement uncertainties. The new adiabatic calorimeter has been successfully tested at the LNE-CNAM. The overall standard uncertainties in the realization of the ITS-90 have been reduced from 2.08 mK to 0.37 mK at the hydrogen triple point, from 1.40 mK to 0.30 mK at the triple point of neon, and are maintained below 0.26 mK at the triple points of oxygen and argon. In the temperature range between 6 K and 24 K, calibrations of rhodium-iron resistance thermometers have been carried out with a standard uncertainty of the order of 0.80 mK. [ABSTRACT FROM AUTHOR]

oustic thermometry is capable of phenomenal accuracy, but is a difficult technique to apply in many practical situations. Here, we describe a modification of the technique, which permits robust temperature measurements to be made, potentially with millikelvin resolution, over a temperature range extending from cryogenic temperatures to over 1000 °C. The technique uses measurements of the time of flight of acoustic pulses in tubes, usually filled with an inert gas such as argon. The tubes-typically made of stainless steel with an outer diameter of 6mm-act as acoustic waveguides and can be several meters long and bent into complex shapes. The time of flight is determined by the average temperature along the entire length of the tube. Local temperature information can be inferred in several ways. Typically a second shorter tube is used and the difference in time of flight reflects the temperature in the region at the end of the first tube. If the measurement length is sufficiently long-typically 1m of tube-then a measurement resolution of less than 1mK is achievable. The technique is well suited to measurements in harsh environments in which conventional sensors degrade. Results from early tests are shown, which highlight the strengths and weaknesses of the technique. [ABSTRACT FROM AUTHOR]