Measuring Systems for Thermometer Calibration in Low-Temperature Range

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?Ciron (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.     

Investigation of the Equivalence of National Dew-Point Temperature Realizations in the ?50?°C to +?20?°C Range

In the field of humidity quantities, the first CIPM key comparison, CCT-K6 is at its end. The corresponding European regional key comparison, EUROMET.T-K6, was completed in early 2008, about 4?years after the starting initial measurements in the project. In total, 24 NMIs from different countries took part in the comparison. This number includes 22 EURAMET countries, and Russia and South Africa. The comparison covered the dew-point temperature range from ?50?°C to +20?°C. It was carried out in three parallel loops, each with two chilled mirror hygrometers as transfer standards in each loop. The comparison scheme was designed to ensure high quality results with evenly spread workload for the participants. It is shown that the standard uncertainty due to the long-term instability was smaller than 0.008?°C in all loops. The standard uncertainties due to links between the loops were found to be smaller than 0.025?°C at ?50?°C and 0.010?°C elsewhere. Conclusions on the equivalence of the dew-point temperature standards are drawn on the basis of calculated bilateral degrees of equivalence and deviations from the EURAMET comparison reference values (ERV). Taking into account 16 different primary dew-point realizations and 8 secondary realizations, the results demonstrate the equivalence of a large number of laboratories at an uncertainty level that is better than achieved in other multilateral comparisons so far in the humidity field.     

Bilateral Comparison of Aluminum Fixed-Point Cells Using Standard Platinum Resistance Thermometer

The objective of Project EURAMET 1114 (Bilateral comparison of a freezing point of aluminum) in the field of thermometry is to compare realization of a freezing point of aluminum (660.323???C) between the Dutch national laboratory VSL and the Slovenian national laboratory MIRS/UL-FE/LMK using a long-stem 25 ?? standard platinum resistance thermometer (SPRT). Both laboratories had participated in a number of inter-comparisons on the level of EURAMET and also on BIPM CCT level (VSL). MIRS/UL-FE/LMK laboratory recently acquired a new fixed-point cell which had to be validated in the process of intercomparison. A quartz-sheathed SPRT was selected and calibrated at MIRS/UL-FE/LMK at the aluminum freezing point and at the water triple point. A second set of measurements was made on the same SPRT and at the same fixed points at VSL (NL). After its return, the SPRT was again recalibrated at MIRS/UL-FE/LMK. In the comparison the W value of the SPRT was used. The results of the internal and external intercomparisons confirmed that the new aluminum cell of the MIRS/UL/FE-LMK realizes a temperature that agrees with the VSL aluminum fixed point within the uncertainty limits of both laboratories. Furthermore, the results of this bilateral-comparison were compared with results that both laboratories achieved in the EURAMET K4 (Project 820) and were found to be in agreement.     

Bilateral Comparison Between CEM and LACOMET in the Range from 83.8058?K to 933.473?K, Linking to CCT Comparisons

A bilateral comparison between Centro Español de Metrología (CEM) and Laboratorio Costarricense de Metrología (LACOMET) in the range from 83.8058 K to 933.473 K was carried out during 2009, and it is aimed to provide linkage of the CCT key comparisons K3 and K4 to LACOMET. This comparison gives support to the calibration measurement capabilities requested by LACOMET. The participation of CEM in the EURAMET regional comparisons EUROMET-T.K3 and EUROMET-T.K4 is the basis of the link. Two 25 ?? standard platinum resistance thermometers (SPRTs) were used as travelling standards and were hand carried. One of them was used only in the aluminum freezing point while the other one covered the remaining fixed points. At the temperature of the argon triple point (83.8058 K), CEM performed the measurements in an argon triple-point apparatus, but LACOMET calibrated the SPRT at a temperature close to the argon point using a liquid-nitrogen boiling-point apparatus. Both SPRTs were provided by LACOMET, and LACOMET measured them before and after CEM. The SPRTs showed no significant drifts during the comparison. The results for both laboratories agreed within their expanded uncertainties and are summarized. A proposal for the linkage to the results of CCT-K3 and CCT-K4 is presented.     

Comparison of Blackbodies for Calibration of Infrared Ear Thermometers

The article presents the results of the EURAMET Project No. 927 ??Comparison of blackbodies for calibration of infrared ear thermometers (IRETs)??. The objective of the comparison was to determine the agreement of blackbodies used for the calibration of IRETs among European national laboratories. To verify the accuracy of an IRET, a suitable blackbody (BB) is needed. Such a blackbody related to the EN standard, designed for the calibration of ear thermometers and immersed in a stirred water bath, was provided for the comparison by the pilot laboratory. The pilot provided also the transfer IRET and organized the comparison.     

Comparison of the Calibration of Standard Platinum Thermometers by Comparison in the Range from $$-80\,^{\circ }\hbox {C}$$ to $$300\,^{\circ }\hbox {C}$$300∘C

In this paper, an interlaboratory comparison in the field of measurement of temperature is presented. Within the comparison, calibration of a standard platinum resistance thermometer (SPRT) by comparisons in the range from \(-80\,^{\circ }\hbox {C}\) to \(300\,^{\circ }\hbox {C}\) was performed. At the same time, in order to support the calibration and measurement capabilities (CMCs) entries of the participating laboratories, we have registered this as EURAMET Project 1251 (Comparison of the calibration of standard platinum resistance thermometers in the range from \(-80\,^{\circ }\hbox {C}\) to \(300\,^{\circ }\hbox {C}\) by comparison). It was recommended that the participants use their standard procedure for the calibration of the standard platinum resistance thermometers and follow instructions from the protocol of EURAMET Project 1251 during the temperature calibration and, if possible, avoid making extra time-consuming measurements. The interlaboratory comparison was organized by the University of Ljubljana, Faculty of Electrical Engineering, Laboratory of Metrology and Quality (MIRS/UL-FE/LMK) in the scope of the IPA 2011 project. The interlaboratory comparison included a maximum of eleven measurement points. However, certain laboratories did not perform measurements at all points in the range. They have performed only measurements in the range that they cover. Prior to the calibration by comparison in each laboratory, a test measurement at the triple point of water or ice point was done in order to assess the stability of the instruments. Results of the comparison show that all the measurements agree within declared uncertainties and thus supporting declared capabilities of the participating laboratories.     

A Study on the EURAMET Comparison of Time Interval Measurement

At April 2003 there were 25 National Metrology Institutes in 25 countries that are members in the European Association of National Metrology Institutes (EURAMETs) agreed to participate in an inter-laboratory comparison for time interval measurement (TIM). The main target of this comparison, as mentioned by EURAMET, was to support the current calibration measurement capabilities for TI and to gain better understanding of the TIM. Cable delay measurement was taken as an example. The time delay of three different length coaxial cables (short, medium, and long) was measured. The majority of the laboratories used the Counter Method. There was a large span between the measurements for all cables (about 1 ns). Consequently, the measurement results that had been published at 2007 were not satisfied for the participant laboratories. In this article, we study the probable reasons for this considerable span between the different measurements for the same artifact.     

Practical Study of Psychrometer Calibrations

Psychrometers remain the most widely used instruments for controlling the humidity in climatic test chambers, yet the calibration of these instruments is particularly challenging. Psychrometer calibrations require careful consideration of influence variables such as the fitting and cleanliness of the wick, the effect of the calibration chamber on the air flow past the sensors, on radiation incident on the sensors, and on the dissipation heat from the built-in fan (if included). In addition, uncertainty requirements for calibration of such psychrometers are typically around 1?%rh to 2?%rh, i.e., close to the best calibration and measurement uncertainties (CMCs) claimed by national metrology institutes (NMIs). As well as their role in supporting CMCs, inter-comparisons provide a good test-ground to ensure all influence variables are controlled or otherwise accounted for in the uncertainty budget. This paper presents the results of a comparison of psychrometer calibrations performed by the NMIs in Denmark, Slovenia, and Finland. The comparison was carried out under EURAMET Project No. 1033 with the aim to investigate the equivalence of psychrometer calibrations performed at the highest level and to gather practical experience to be used in similar comparisons in the future. An aspirated electro-psychrometer was used for the comparison, and calibrations were carried out in the range from 15 %rh to 93?%rh in a temperature range from 15?°C to 70?°C. While the results show good agreement at high relative humidity, significant differences at low relative humidity are reported. It is suggested that the differences are caused by a combination of psychrometer wick contamination and a difference in the wick-wetting methods used by the participant laboratories.     

Bilateral Comparison of Mercury and Gallium Fixed-Point Cells Using Standard Platinum Resistance Thermometer

The objective of project EURAMET 1127 (Bilateral comparison of triple point of mercury and melting point of gallium) in the field of thermometry is to compare realization of a triple point of mercury (?38.8344 °C) and melting point of gallium (29.7646 °C) between the Slovenian national laboratory MIRS/UL-FE/LMK and the Croatian national laboratory HMI/FSB-LPM using a long-stem 25 ?? standard platinum resistance thermometer (SPRT). MIRS/UL/FE-LMK participated in a number of intercomparisons on the level of EURAMET. On the other hand, the HMI/LPM-FSB laboratory recently acquired new fixed-point cells which had to be evaluated in the process of intercomparisons. A quartz-sheathed SPRT has been selected and calibrated at HMI/LPM-FSB at the triple point of mercury, the melting point of gallium, and the water triple point. A second set of measurements was made at MIRS/UL/FE-LMK. After its return, the SPRT was again recalibrated at HMI/LPM-FSB. In the comparison, the W value of the SPRT has been used. Results of the bilateral intercomparison confirmed that the new gallium cell of the HMI/LPM-FSB has a value that is within uncertainty limits of both laboratories that participated in the exercise, while the mercury cell experienced problems. After further research, a small leakage in the mercury fixed-point cell has been found.     

Intercomparison of the Dew-Point Temperature Realizations at LPM and MIKES in the Range from ?70?°C to +?20?° C

The first European humidity key comparison EURAMET-T.K6 was completed in 2008, and it covered the dew-point temperature range from ?50?°C to +?20?°C. Both LPM and MIKES participated in the comparison, but a new low dew-point generator was introduced at LPM as a result of progress in the EUROMET P912 project. To extend the range of available comparison evidence down to ?70?°C and to study the validity of improved uncertainties of LPM, a bilateral comparison was carried out between LPM and MIKES in 2009?C2010. The applied comparison procedure was similar to that applied in EURAMET-T.K6. However, only one transfer standard was used instead of two units and the measurement point ?70?°C was added in the measurement scheme. The results show that the bilateral equivalence between LPM and MIKES is between (0.00 ± 0.06)?°C and (0.02 ± 0.08)?°C in the range from ?50?°C to +?20?°C and (0.01 ± 0.10)?°C at ?70?°C. Using MIKES results as the link to the EURAMET.T-K6, it is shown that the difference between the results obtained with the new LPM dew-point temperature standard and the EURAMET Comparison Reference Values is between (?0.02 ± 0.08)?°C at 20?°C and (+?0.02 ± 0.07)?° C at ?50?°C.     

Development of the Triple-Point-of-Argon System

A triple-point-of-argon system was developed to realize the argon triple-point temperature defined in the International Temperature Scale of 1990 (ITS-90) and to calibrate long-stem standard platinum resistance thermometers (SPRTs). The system structure, the techniques for realization of the triple-point temperature, and the testing results are presented in this paper. In this system, there is a central argon cell that includes four re-entrant wells with an immersion depth of 160?mm which can be used to calibrate four long-stem SPRTs simultaneously. A high-accuracy temperature controller is used to control the realization process of the argon triple-point temperature plateau. The argon triple-point plateau can be easily realized with this system. The influence of different experimental parameters on the triple-point-of-argon plateau was investigated and is discussed. The testing results show that the duration of the plateau can be over 100?h with the temperature change less than 0.05?mK. The temperature homogeneity of the four re-entrant wells was tested. The immersion profile of the system was measured, and the measurement results were compared with the ITS-90 hydrostatic values. The uncertainty analysis shows that the uncertainty of the argon system is 0.25?mK (k = 2).     

Comparison of Air Temperature Calibrations

European national metrology institutes use calibration systems of various types for calibrating thermometers in air. These were compared to each other for the first time in a project organized by the European Association of National Metrology Institutes (EURAMET). This EURAMET P1061 comparison project had two main objectives: (1) to study the equivalence of calibrations performed by different laboratories and (2) to investigate correlations between calibration methods and achievable uncertainties. The comparison was realized using a pair of 100  \(\Omega \) platinum resistance thermometer probes connected to a digital thermometer bridge as the transfer standard. The probes had different dimensions and surface properties. The measurements covered the temperature range between \(-40\,^{\circ }\mathrm{{C}}\) and \(+150\,^{\circ }\mathrm{{C}}\) , but each laboratory chose a subrange most relevant to its scope and performed measurements at five nominal temperature points covering the subrange. To enable comparison between the laboratories, comparison reference functions were determined using weighted least-squares fitting. Various effects related to variations in heat transfer conditions were demonstrated but clear correlations to specific characteristics of calibration system were not identified. Calibrations in air and liquid agreed typically within \(\pm 0.05\,^{\circ }\mathrm{{C}}\) at \(+10\,^{\circ }\mathrm{{C}}\) and \(+80\,^{\circ }\mathrm{{C}}\) . Expanded uncertainties determined by the participants ranged from \(0.02\,^{\circ }\mathrm{{C}}\) to \(0.4\,^{\circ }\mathrm{{C}}\) and they were shown to be realistic in most cases.     

CCT-K7水三相点容器国际关键比对

在国际互认框架内,国家计量标准的国际等效性是通过国际计量委员会（CIPM）的咨询委员会组织的一系列国际关键比对来确定的。温度咨询委员会（CCT）委托国际计量局（BIPM）作为主导实验室组织了由20个国家实验室参加的CCT-K7水三相点容器国际关键比对。比对结果表明：这些国家基准水三相点值在0．171mK范围内一致。此外,为了减小国家实验室复现水三相点的系统差,需要进一步研究同位素组成对水三相点温度的影响以及同位素修正。     

Effect of Impurities on Water Triple-Point Cells

Water triple-point cells are the basis for the definition of the kelvin and for the realization of the International Temperature Scale of 1990. The temperature differences between the cells are mainly caused by impurities arising in the cell water from the dissolution of the cell envelope (borosilicate glass or quartz). In order to investigate the effects of such impurities on the realized triple-point temperature, water triple-point cells doped with known amounts of Si and Na impurities ( \(0.1\,{\upmu }\hbox {mol}{\cdot }\hbox {mol}^{{-1}}\) to \(1\,{\upmu }\hbox {mol}{\cdot }\hbox {mol}^{{-1}}\) of Si and \(0.2\,{\upmu }\hbox {mol}{\cdot }\hbox {mol}^{{-1}}\) to \(2\,{\upmu }\hbox {mol}{\cdot }\hbox {mol}^{{-1}}\) of Na) were manufactured at VSL by adding gravimetric mixtures of a Si standard reference material and ultra high-purity water to the cell high-purity water. Water samples were taken from the manufactured cells, partitioned into three samples, and distributed to different laboratories for isotope and impurity analysis (inductively coupled plasma mass spectrometry, ICPMS). The results of two independent ICPMS analyses were compared with impurity calculations based on the gravimetric data of the prepared mixtures and manufactured cells. One undoped cell manufactured by UME and one undoped cell manufactured by VSL were intercompared at both VSL and SMD to demonstrate the equivalence of the manufacturing processes of UME and VSL. The triple-point temperatures realized by the doped cells and the undoped cell manufactured by VSL were measured at SMD. The results showed that, in doped cells, the equilibration time after the last freezing is directly dependent on the impurity concentration, and the temperature depression of doped triple-point-of-water cells is significantly greater than the values predicted by Raoult’s law for an ideal dilute solution.     

An Alternative Method for Manufacturing Water Triple-Point Cells

Water triple-point (WTP) cells are the most important standards in laboratories that calibrate standard platinum resistance thermometers (SPRT). Over the years, different methods for manufacturing WTP cells have been proposed; some quite simple, others more complex. This paper describes a straightforward method for manufacturing WTP cells. The method is based on the fact that the pressure present when water is boiling is its vapor pressure, and because of that the amount of residual dissolved gases, if any, is very small. This makes the use of vacuum pumps unnecessary. The bulb of the WTP cell is filled with pure water produced by multiple distillations or by deionizer systems. The water is then boiled inside the bulb by a furnace built specifically for this purpose. After boiling the water for at least 30 min, the furnace is switched off, and a valve connected to the filling port of the cell is closed, in order to ensure that only water vapor and liquid water are present inside the WTP cell. The cell is then removed from the furnace and sealed when its temperature decreases. The paper also describes the procedure used to evaluate the WTP cells manufactured by this method, through comparisons against other reference standards, manufactured by more traditional approaches. The results show that the temperatures of the WTP cells manufactured by this new method have similar values to the ones obtained in WTP cells manufactured by traditional methods.     

International comparison of thermal noise-temperature measurementsat 2, 4, and 12 GHz

We discuss an international comparison of thermal noise-power measurements (GTRF-92-2), which has recently been completed under the auspices of the Consultative Committee for Electricity and Magnetism (CCEM). The noise temperatures of two solid-state sources with GPC-7 connectors were measured at 2, 4, and 12 GHz at the national laboratories in France, Germany, the United Kingdom, and the United States. Good agreement was found among the results from the different laboratories, with all results agreeing within the expanded uncertainties, which ranged from approximately 0.5% to 2.9%. The comparison was performed in accordance with the guidelines recently adopted by the Bureau International des Poids et Mesures (BIPM)     

First Interlaboratory Comparison on Calibration of Temperature-Controlled Enclosures in Turkey

The number of accredited laboratories in the field of calibration of temperature-controlled enclosures has been increasing in Turkey. One of the main criteria demonstrating the competence of a calibration laboratory is successful participation in interlaboratory comparisons. Therefore, TUBITAK UME Temperature Laboratory organized the first interlaboratory comparison on “Calibration of Temperature-Controlled Enclosures” in Turkey as a pilot laboratory between January and November, 2013. Forty accredited laboratories which provide routine calibration services to the industry in this field participated in the comparison. The standards used during the comparison was a climatic chamber for the measurements at \(-40\, {^{\circ }}\hbox {C},\,-20\, {^{\circ }}\hbox {C}, 40\, {^{\circ }}\hbox {C}\) and \(100\, {^{\circ }}\hbox {C}\) and an oven for the measurements at \(200\, {^{\circ }}\hbox {C}\). The protocol of the comparison was prepared considering guide EURAMET cg-20 and BS EN/IEC standards 600068-3-5 and 600068-3-11. During the comparison measurements, each participant had the liberty to choose the most convenient calibration points in terms of their accreditation scope among the values mentioned above and carried out on-site measurements at UME. The details and the results of this comparison are given in the paper. Determination of the statistical consistency of the results with the uncertainties given by the participants can be assessed by the method of \(E_{n}\) value assessment for each laboratory. \(E_{n}\) values for all measurement results based on the results of pilot and participating laboratories were calculated.     

Progress Towards the Determination of the Relationship of Triple-Point Temperature versus Isotopic Composition of Neon

Following the finalization of the work performed to establish the triple-point temperature versus isotopic composition relationship for protium (Metrologia 42, 171 (2005)) adopted into the ITS-90 definition by the International Committee for Weights and Measures (CIPM) in 2005, and a preliminary exploration of the variability in the triple-point temperature of neon gas samples arising from differences in isotopic composition (Anal. Chem. 77, 5076 (2005)), this article reports further progress toward the determination of a similar comprehensive relationship for neon, to be included in a future revision of the Technical Annexe to the ‘mise en pratique’ of the kelvin. This progress article mainly concerns a set of gas samples used for the neon triple-point measurements during CCT-K2, and subsequently, others for which the isotopic compositions were recently measured. Recent high accuracy measurements of the corresponding thermal data are now available for many of these samples, but not yet for all of them.     

医用加速器光子水吸收剂量国际比对及进展

医用加速器光子水吸收剂量国际比对采用星式比对方式,主导实验室为国际计量局,其石墨量热计复现的水吸收剂量为比对参考值.各国计量实验室依据各自医用加速器辐射质参数,进行2～3个辐射质的水吸收剂量绝对测量,现已完成7个国家的比对工作,比对数据公布在关键比对数据库中.     

A European Roadmap for Thermometry

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.