Search

Three European National Metrology Institutes (NMIs), VSL, LNE-CETIAT and INRiM, extended their relative humidity calibration capabilities to temperatures up to 170 °C, dew-point temperatures up to 150 °C and pressures up to 600 kPa. In order to test the equivalence of the respective calibration set-ups, 4 commercial high-temperature relative humidity sensors were exchanged among the three NMIs and calibrated at different combinations of relative humidity (19 %rh to 70 %rh), air temperature (100 °C to 170 °C) and pressure (100 kPa to 500 kPa), realizing dew-point temperatures of either 81.5 °C or 127 °C. The initial and final measurements at VSL showed that the stability of the selected sensors was sufficient for comparing the different calibration set-ups. The results of the comparison showed that VSL and LNE-CETIAT facilities agreed within their claimed uncertainties (≤0.3 %rh), while discrepancies of up to 4 %rh were observed between VSL and INRiM facilities.

In the field of water content measurement, the calibration of coulometric methods (e.g., coulometric Karl Fischer titration or evolved water vapor analysis) is often overlooked. However, as coulometric water content measurement methods are used to calibrate secondary methods, their results must be obtained with the highest degree of confidence. The utility of calibrating such instruments has been recently demonstrated. Both single and multiple point calibration methods have been suggested. This work compares these calibration methods for the evolved water vapor analysis technique. Two uncertainty estimation approaches (Kragten’s spreadsheet and M-CARE software tool) were compared as well, both based on the ISO GUM method.

International audience; Moisture content can affect the thermo-physical properties of many materials. Thus sufficient knowledge of this parameter is required to improve product shelf life and quality, reduce waste or enhance process efficiency. The traditional loss on drying methods are still the go-to methods due to their robustness and simplicity. How-ever, their inherent lack of selectivity imposes restrictions. These are overcome with newer techniques such as vaporization coulometric Karl Fischer titration (vap-C-KFT) and evolved water vapor analysis (EWV). The former is a well-established method, but the latter was more recently introduced and the literature available on it is scarce. This work aims to bridge this gap in knowledge and demonstrate the com-parability of the EWV to the more established vap-C-KFT. Multiple samples were studied and the data are analyzed along the principles reported recently by INRiM with a few modifications.

Gas-Controlled Heat Pipes (GCHPs) are devices based on generating and maintaining, at millikelvin level, a thermodynamic liquid-vapour equilibrium of a fluid. For this reason, GCHPs have been studied for more than thirty years for research and applications in thermal metrology. Capabilities have been constantly improved and adapted by National Metrology Institutes (NMIs) and accredited laboratories. Activities include study of vapour pressure curves of pure elements and substances, thermometers’ non-uniqueness up to 960 °C, calibrations between −20 °C and 900 °C with millikelvin uncertainties, studies of innovative pressure controllers allowing regulation better than 10−6 from below 1000 Pa up to 400 kPa. GCHPs operating at different temperature ranges have also been connected to a common pressure line in the so-called “Temperature Amplifier” configuration. This review paper presents an almost complete report about the several models of GCHPs, materials and working fluids, techniques adopted in different temperature/pressure ranges. All involved NMIs using GCHP are here included, with detailed bibliography.

The study consists in quantifying the effect of the thermal radiation of the climatic chamber walls on air temperature measurements for contact thermometry. Air temperature measurements are affected by surface interactions with the environment, such as those of the thermometer and walls (surface condition, emissivity and air velocity). The walls of the enclosure are generally made of stainless steel, a potentially radiating material. To characterize the effect of the walls, we have varied environmental conditions such as the emissivity of the walls of the chamber and the sensors, the surface of the sensors, temperature and illumination. These different configurations allow us to deduce their impacts on the temperature measurements. To quantify this effect we simulated different configurations to isolate the radiation effect. Two surface states are tested: low emissivity metal surface and painted surface with matte black paint of high emissivity. This study highlights the effect of the walls on the air temperature measurements in the center of the climatic chamber. The experimental results were also subject to a theoretical verification using the equation of the standard ISO 7726 [1]. The quantification of the effect of radiation from the walls of the climate chamber on temperature measurements becomes significant from 100 °C. Quantification of thermal radiation is 0.4 °C at 100 °C and 0.8 °C at 150 °C.

In this study, broadband dielectric properties of water in compacted kaolinite clay are investigated. Two types of analysis are applied, a thermo-coulometric analysis also called “evolved water vapor” is used to identify the different bounding forms of water and the analysis of the transformation of dielectric modulus from dielectric permittivity measurements. A correlation between differently bound water fractions in kaolinite clay are identified by combining these analyses during water uptake and drying process. Water content dependence with the electric modulus strength peaks in RF (radiofrequency) range is studied.

Nowadays, a precise knowledge of permittivity became essential in several domains. Correlation between temperature and dielectric permittivity is necessary, especially in the target applications of radio frequencies and microwave systems like biomedical applications, aeronautics… Furthermore, moisture content in a material has a significant impact. In some countries temperature can vary a lot during a day and affect characterization measurement like Ground Penetration Radar (GPR) measurement. In this way correlation between Temperature and moisture content became important. In this paper, we propose a technical system to measure the influence of temperature on the dielectric permittivity of a water / kaolinite clay mixture. We use a measurement setup based on a coaxial line system upgraded with a heating component. In this study, we present some results and comparisons on Kaolinite with different moisture content.

The study describes significant outcomes of the Metrology for Meteorology' project, MeteoMet, which is an attempt to bridge the meteorological and metrological communities. The concept of traceability, an idea used in both fields but with a subtle difference in meaning, is at the heart of the project. For meteorology, a traceable measurement is the one that can be traced back to a particular instrument, time and location. From a metrological perspective, traceability further implies that the measurement can be traced back to a primary realization of the quantity being measured in terms of the base units of the International System of Units, the SI. These two perspectives reflect long-standing differences in culture and practice and this project - and this study - represents only the first step towards better communication between the two communities. The 3 year MeteoMet project was funded by the European Metrology Research Program (EMRP) and involved 18 European National Metrological Institutes, 3 universities and 35 collaborating stakeholders including national meteorology organizations, research institutes, universities, associations and instrument companies. The project brought a metrological perspective to several long-standing measurement problems in meteorology and climatology, varying from conventional ground-based measurements to those made in the upper atmosphere. It included development and testing of novel instrumentation as well as improved calibration procedures and facilities, instrument intercomparison under realistic conditions and best practice dissemination. Additionally, the validation of historical temperature data series with respect to measurement uncertainties and a methodology for recalculation of the values were included.

A European research project METefnet addresses a fundamental obstacle to improving energy-intensive drying process control: due to ambiguous reference analysis methods and insufficient methods for estimating uncertainty in moisture measurements, the achievable accuracy in the past was limited and measurement uncertainties were largely unknown. This paper reports the developments in METefnet that provide a sound basis for the SI traceability: four new primary standards for realizing the water mass fraction were set up, analyzed and compared to each other. The operation of these standards is based on combining sample weighing with different water vapor detection techniques: cold trap, chilled mirror, electrolytic and coulometric Karl Fischer titration. The results show that an equivalence of 0.2 % has been achieved between the water mass fraction realizations and that the developed methods are applicable to a wide range of materials., The SIB64 METefnet project is funded by the European Metrology Research Programme (EMRP) that is jointly funded by the EMRP participating countries within EURAMET and the European Union.

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.

In order to improve the efficiency of moisture meters calibrations, we studied the effect of ambient humidity, sample handling, packing and transportation on the timber wood (spruce) moisture determination. It was proved by experiments that dry timber samples ( $$12 \times 12 \times 2.5$$ cm) reach equilibrium within 30–40 days even when moisturizing them at a high relative air humidity (80 %). On the other hand, the major mass loss of moist samples placed at normal laboratory conditions was found to occur during the first few days while the first 5 days are critical. The effects of sample handling, packing and transportation were studied by means of interlaboratory comparison between CMI, CETIAT, INRIM, NIS and KRISS. The obtained results show that samples with moisture content less than 7 % tend to absorb small amount of water, whereas samples with moisture content larger than 15 % tend to desorb small amount of water during the handling and transporting even when using vacuum packing and short handling times.

The CETIAT thermometry calibration laboratory has a wide range of temperature generators. Overflow baths, dry furnaces, furnaces as well as thermostatic chambers make it possible to achieve a temperature range from −90 °C to 1050 °C. Experience gained over more than ten years enables the teams to identify possible measurement difficulties. The thermal characterisation of portable furnaces is identified as risks in measurement errors. The diversity of CETIAT’s calibration tools makes it possible to highlight these risks and to find solutions for them. Only a few documents deal with the characterisation of portable furnaces. The EURAMET guide “cg-13 form 3.0 (02/2015)” provides some elements. This lack of information on implementation in temperature calibration furnaces can lead to significant calibration errors. A calibration performed in a thermostated bath or dry furnace will give different results in both the correction and the associated uncertainty. The difference in the results obtained is such that the corrections do not overlap, even when taking into account the associated uncertainties. There is also the effect of the environment on the results. This study allows users of portable furnaces to reduce measurement errors due to poor implementation.

Humidity is a key parameter in controlling drying processes and ambient conditions in many industrial manufacturing, storage and test applications. Air humidity is routinely measured at temperatures above 100 °C and at conditions that are often challenging due to temporal and local variations. Calibrations of humidity sensors do not provide appropriate representativeness of measurement conditions because they are limited to temperatures below 100 °C and static conditions. A European metrology research project HIT (“Metrology for Humidity at High Temperatures and Transient conditions”) is developing improved humidity measurement and calibration techniques to temperatures up to 180 °C and non-static conditions. This paper summaries developments of the project: calibration and test facilities for industrial hygrometers, studies on humidity control in specific microbial transient processes and a new measurement approach for water activity measurements.

CETIAT is a calibration laboratory accredited by COFRAC. The temperature generators are stirred calibration baths (from −80 °C up to +215 °C), dry blocks and furnaces (from −90 °C up to +1050 °C) and thermostatic chamber (from −30 °C up to +160 °C). The best calibration uncertainty is achieved in calibration bath, for Platinum Resistance Thermometers (PRTs), it is 0.03 °C. Nevertheless, the daily calibrations lead to an uncertainty about 0.06 °C for industrial RTD sensors. The CETIAT is working on the implementation of a Gas Controlled Heat Pipe (GCHP) temperature generator to replace the thermometric baths in order to increase productivity and in order to improve temperature stability in the working volume of the generator. Many studies [1, 2], explain the advantage of this method. For this purpose, the new system must have better thermal performance and produce the same temperature range than the stirred baths.Two years ago, the CETIAT characterized a water GCHP for industrial applications cover the temperature range from +30 °C up to +150 °C [3]. The results were in good agreement with the expectations and water GCHP could be used to calibration production. But, we need to extend the temperature range towards the low temperatures. This year, the CETIAT characterized a new type of ethanol’s heat pipe. We used the same heat pipe but this time we replaced water by ethanol. The possibilities of using ethanol, would allow generation of temperatures between −40 °C and 30 °C low temperature enclosure.This article presents the first results on the study of a low temperature heat pipe made at CETIAT. The results obtained during the metrological characterization, in terms of temperature homogeneity and stability, in this study are encouraging. However, an issue with the stability of the cooling system diminish the quality of the results. The stability of the surrounding environment must be improved. This will be the subject of a future study. The results at 20 °C are very positive. Over an axial length of 250 mm, the thermal homogeneity is less than 5 mK.

International audience; The determination of the physical properties of pure water, especially the vapor-pressure curve of water, is one of the major issues identified by the Consultative Committee for Thermometry of the International Committee for Weights and Measures (CIPM) to improve the accuracy of the national references in humidity. At the present time the saturation-pressure data, corresponding to ice or liquid-vapor equilibrium, at low temperature are scarce and unreliable. This study presents new measurements of vapor and sublimation pressures of, respectively, water and ice, using a static apparatus. Prior to saturation-pressure measurements, the temperature and pressure sensors of the static apparatus were calibrated against reference gauges in use at the LNE-CETIAT laboratories. The effect of thermal transpiration has been studied. The explored temperature range lies between 250 K and 374 K, and the pressure range between 70 Pa and 10(5) Pa. An automatic data acquisition program was developed to monitor the pressure and temperature. The obtained results have been compared with available literature data. The preliminary uncertainty budget took into account several components: pressure measurements, temperature measurements, and environmental error sources such as thermal transpiration and hydrostatic correction.

Broadband electromagnetic characterization offers useful tools for the quantitative estimation of water content in a insulating solid materials. However, the correlation between electromagnetic cha ...

Launched in 2011 within the European Metrology Research Programme (EMRP) of EURAMET, the joint research project ‘MeteoMet’—Metrology for Meteorology—is the largest EMRP consortium; national metrology institutes, universities, meteorological and climate agencies, research institutes, collaborators and manufacturers are working together, developing new metrological techniques, as well as improving existing ones, for use in meteorological observations and climate records. The project focuses on humidity in the upper and surface atmosphere, air temperature, surface and deep-sea temperatures, soil moisture, salinity, permafrost temperature, precipitation, and the snow albedo effect on air temperature. All tasks are performed using a rigorous metrological approach and include the design and study of new sensors, new calibration facilities, the investigation of sensor characteristics, improved techniques for measurements of essential climate variables with uncertainty evaluation, traceability, laboratory proficiency and the inclusion of field influencing parameters, long-lasting measurements, and campaigns in remote and extreme areas. The vision for MeteoMet is to take a step further towards establishing full data comparability, coherency, consistency, and long-term continuity, through a comprehensive evaluation of the measurement uncertainties for the quantities involved in the global climate observing systems and the derived observations. The improvement in quality of essential climate variables records, through the inclusion of measurement uncertainty budgets, will also highlight possible strategies for the reduction of the uncertainty. This contribution presents selected highlights of the MeteoMet project and reviews the main ongoing activities, tasks and deliverables, with a view to its possible future evolution and extended impact.

Bien que les mesures de teneur en eau soient largement utilisees dans l’industrie, les considerations metrologiques quant a cette mesure ne sont pas completement abouties de sorte a fournir des mesures fiables et tracables au SI. Afin de remedier a ceci, le projet de recherche conjoint, Joint Research Project SIB64 “METefnet - Metrology for moisture in materials”, est actuellement en cours, et contribue au programme europeen de recherche en metrologie European Metrology Research Programme. Le projet METefnet a pour objectifs de developper et d’ameliorer l’approche metrologique de ce sujet. Ceci inclus notamment: le travail sur de nouvelles methodes de reference pour evaluer la fraction massique en eau, l’amelioration des mesures mettant en œuvre la methode primaire de type titration Karl Fischer, le developpement de nouveaux materiaux de reference certifies presentant une tres bonne stabilite et permettant une tracabilite au SI, le developpement de nouveaux etalons de transfert, la realisation d’etudes visant a quantifier et reduire les effets lies a la prise d’echantillon, son transport et sa manipulation, le developpement d’une nouvelle methode pour etalonner les instruments mesurant l’humidite de surface, et l’amelioration des methodes d’estimation d’incertitudes de ces mesures. Ce travail, realise dans le domaine de la metrologie de l’humidite au sein des materiaux, couvre a la fois le mesurande decrit comme etant specifiquement la teneur en eau, seule, dans les materiaux, mais egalement un mesurande plus large pouvant inclure l’eau ainsi que d’autres liquides ou composes organiques volatiles; ceci afin de bien mettre en exergue la difference qui peut etre observee entre ces deux mesurandes. Le projet global a pour objectif de soutenir une action de dissemination et de tracabilite au systeme SI des mesures de teneur en eau dans les materiaux avec une exactitude optimale et de developper une infrastructure metrologique coherente pour ce type de mesures. Le travail technique ainsi que les dernieres avancees vous sont ainsi presentees.

Les hygromètres sont largement mis en oeuvre pour des conditions de température supérieures à 100°C et dans des conditions de régimes dynamiques. Cependant, la plupart des laboratoires européens ne peuvent fournir d'étalonnages qu'à des températures relativement basses et dans des conditions de régimes établi et stables. Il apparaît donc nécessaire de développer de nouvelles techniques et méthodes d'étalonnage de sorte à élargir la gamme des possibilités d'étalonnage et de garantir ainsi une traçabilité qui soit en adéquation avec les besoins industriels. Ces développements sont d'autant plus importants vis-à-vis des besoins de mesure à hautes températures, en régimes dynamiques et pour les mesures d'activité de l'eau. Les conditions de mesures d'humidité en régimes transitoires et dynamiques sont une composante à part entière des environnements industriels d'essai et de test et il n'existe actuellement aucune méthode permettant l'estimation d'incertitudes dans de telles situations. Cet article met en avant un nouveau projet européen de recherche en métrologie - HIT: "Metrology for Humidity at high Temperature and Transient conditions". Ce projet a été construit de sorte à améliorer significativement l'exactitude des mesures d'humidité jusqu'à des températures de 180°C et en régimes dynamiques en contexte industriel, au travers de l'amélioration des techniques de mesure et d'étalonnage. Les principaux bénfices que doit apporter ce projet, sont l'extension des gammes d'étalonnages industriels à haute température et en régimes dynamiques, l'établissement de nouvelles méthodes de mesure d'humidité en régime dynamique et en présence de variations spatiales ainsi que le développement de nouvelles méthodes de mesure d'activité de l'eau "en ligne" sur les procédés industriels. L'ensemble de ces développements seront validés et illustrés au travers d'applications industrielles.

This paper presents physical principles involved and main errors encountered when performing surface temperature measurements, in contact thermometry. Two concepts are defined: direct temperature measurements where the objective is to evaluate the surface temperature that prevailed prior to the application of the sensor and indirect measurements using surface sensors to assess, for example, the internal temperature of a fluid flowing in a pipe or within a wall. It is important to define the quantity of interest, i.e . the measurand, because the same sensor can be used but implemented differently. For example, for direct measurement, sensors can be calibrated on surface temperature calibrator and should be applied directly on the surface that should be measured. Whereas, for indirect measurements, improving the thermal contact can be achieved by using a thermal dough or sensor insulation and calibration should be realized on site. To illustrate these situations and these phenomena, various measurements of industrial surface temperature are provided. For example, it is important, in an industrial mixing process, to control the mixer surface temperature to ensure the quality of the finished mixed product. The temperature of the machine housings has also to be controlled to prevent the risk of burns. Energy audits can also be based on such measures. Surface temperature sensors are more and more present in the controls of heating and air-conditioning systems such as heat pumps, boilers ... Surface temperature often help saving time during manufacturing and during maintenance operations. Over the past decade, the performances of such sensors has been much improved.This article outlines the precautions and best practices for implementation of the contact temperature sensors. The environmental effects are studied in order to quantify the impact on the measurements. The concepts developed by Bardon, Cassagne and Sacadura are used to explain the effects present at the interface. The effects of an air flow, the radiation, thermal conductivity of the wall, the fixing system of the sensor are studied for an optimal implementation of relevant solutions. The paper offers an overview of current implementations techniques and possible performance levels.

Le LNE-CETIAT fait partie d’un consortium, de laboratoires nationaux de metrologie, implique dans un projet europeen de recherche en metrologie (Joint Research Project) denomme SIB64 METefnet (http://www.metef.net) et finance par le comite European Metrology Research Programme (EMRP). L’objectif du projet est de permettre aux utilisateurs finaux de realiser des mesures d’humidite dans les solides, fiables et tracables au SI, en ameliorant les techniques de mesure et les methodes d’etalonnage [1]. Parmi les differentes approches suivies par les partenaires de ce projet, le LNE-CETIAT a choisi de se concentrer sur la dissemination de la tracabilite au SI, a l’endroit d’utilisateurs industriels, en developpement un instrument de transfert non destructif utilisant des Hautes-Frequences et des micro-ondes, a bas niveau d’energie (0dBm), pour mesurer l’humidite dans les materiaux solides.La frequence de relaxation de l’eau dans un materiau depend, notamment, du degre de liaison entre les molecules d’eau et la matrice solide (substrat) [2–3]. La bande de frequences couvre un spectre qui s’etend des Hautes-Frequences -HF, soit de quelques MHz a quelques centaines de MHz, aux Micro-Ondes -MO, soit de quelques centaines de MHz a quelques GHz. Ainsi, il est communement considere, par les constructeurs utilisant les ondes electro-magnetiques -OEM comme moyen de chauffage dans les procedes de sechage, que l’eau liee physiquement ou chimiquement, a la matrice solide, interagit principalement et selectivement avec les ondes du domaine RF, tandis que l’eau libre, dans la matrice solide, interagit principalement avec les MO (10 GHz).L’instrument developpe dans le cadre de ce projet exploite cette selectivite, vis-a-vis du type d’OEM utilisee, en faisant des mesures de proprietes dielectriques des materiaux humides. Ce principe de mesure est connu et utilise depuis les annees 70, les instruments alors developpes fonctionnant exclusivement soit en RF soit en MO et sur bande de frequence extremement etroite. Ces appareils ne permettent donc pas de couvrir une large gamme de frequence de sorte a optimiser la frequence de mesure vis-a-vis du degre de liaison de l’eau avec la matrice solide. L’originalite de ce travail repose sur la mise au point d’un instrument de mesure dont la frequence de travail, utilisee pour mesurer l’humidite dans une matrice solide, est optimisee vis-a-vis de degre de liaison de l’eau avec le substrat et vis-a-vis de l’interaction entre l’OEM et le materiau. Pour ce faire, plus la frequence de travail du capteur sera proche de la frequence de relaxation mesuree plus la sensibilite de l’instrument sera bonne. Afin de determiner la frequence de relaxation de l’eau dans un solide, le CETIAT developpe un equipement qui permet de couvrir une gamme de frequences la plus grande possible. Pour ce besoin, deux cellules, non-resonnantes, ont ete developpees : une cellule capacitive et une cellule coaxiale. Cet article presente les cellules developpees ainsi que les premiers resultats experimentaux obtenus avec la cellule capacitive.

Afin d’estimer, le mieux possible, les erreurs de justesse des appareils en etalonnage, les laboratoires recherchent a generer des environnements le mieux controles possible.. Les mesures d’humidite, en milieu industriel, sont tres eloignees de ces conditions d’etalonnage en laboratoire. Ainsi, meme si l’etalonnage constitue un point de depart necessaire pour maitriser son processus de mesure, il ne permet pas toujours une description complete de la reponse ou du comportement de l’instrument. La norme francaise NF X15–113 [1] propose des essais complementaires visant a parfaire la description de la reponse ou du comportement d’un hygrometre. Elle presente une serie d’essais visant a qualifier les hygrometres a variation d’impedance de type capacitif ou resistif. La partie technique de la norme, exposant les essais a conduire, se compose de deux paragraphes: le premier est dedie aux essais generiques du capteur en humidite et en temperature notamment; le deuxieme porte davantage sur les erreurs/effets liees aux facteurs d’influence. Dans le cadre du developpement d’un hygrometre, specifiquement adapte a l’industrie du secteur nucleaire, la societe Michell Instruments et le CETIAT ont collabore a la mise en œuvre le plus largement possible des essais proposes par la NF X15–113. Le CETIAT a ainsi developpe specialement des bancs d’essais visant a realiser les essais en humidite et en temperature qui y sont decrits. Cet article presente les principes, les conditions environnantes, les sequences et les conditions des essais permettant d’appliquer cette norme. Nous pourrons distinguer les essais realises dans des conditions statiques ou d’equilibre: les etalonnages initiaux et finaux, les essais sur le domaine des temperatures nominales, et limites, les essais de derive thermique du conditionneur de signal; le but de ces essais est d’etablir l’erreur de justesse de l’instrument lorsqu’il est expose aussi bien dans des conditions normales de temperature que dans des conditions extremes de temperature et d’humidite. Ensuite, nous pourrons distinguer les essais realises dans des conditions dynamiques ou transitoires: temps reponse suite a l’application d’un echelon d’humidite, ou a l’application d’un echelon de temperature; le but de ces essais est d’etudier la reponse de l’hygrometre en essais lors de l’application de stimuli transitoires en temperature et en humidite. Enfin nous distinguerons les essais permettant d’evaluer le temps de recuperation de l’instrument suite a la formation de condensation ou suite a l’immersion de l’hygrometre; le but de ces essais est de detecter toute derive, reversible ou permanente, suite a l’exposition a l’eau de l’element sensible. Ce travail se concentre sur les points cles de chaque essai et l’interet qu’il peut representer pour l’utilisateur final lorsque son instrumentation est confrontee a ces conditions. Une attention particuliere est portee sur les astuces et les difficultes pouvant survenir lors de la realisation de ces essais.

Climate change and its consequences require immediate actions in order to safeguard the environment and economy in Europe and in the rest of world. Aiming to enhance data reliability and reduce uncertainties in climate observations, a joint research project called MeteoMet-Metrology for Meteorology started in October 2011 coordinated by the Italian Istituto Nazionale di Ricerca Metrologica (INRiM). The project is focused on the traceability of measurements involved in climate change: surface and upper air measurements of temperature, pressure, humidity, wind speed and direction, solar irradiance and reciprocal influences between measurands. This project will provide the first definition at the European level of validated climate parameters with associated uncertainty budgets and novel criteria for interpretation of historical data series. The big challenge is the propagation of a metrological measurement perspective to meteorological observations. When such an approach will be adopted the requirement of reliable data and robust datasets over wide scales and long terms could be better met. © 2013 AIP Publishing LLC.

Expert systems have been developed for the diagnosis of turbine generators, and are heuristic-based systems. The level of diagnostic explanations they provide to their end users is questionable. This paper presents and discusses the results of case- and model-based reasoning techniques for diagnosing and explaining faults of turbine generators. The techniques provide explanations that match user's expectations and reflect less ‘human expert rules’. This also led to the design of a new generation of smart systems which will explain and persuade better plant operators that their diagnosis was correct.

La constante de temps thermique d’un corps homogene est un parametre couramment utilise pour l’etude dynamique des processus d’echauffement et de refroidissement. Dans les cas de transferts par convection naturelle ou forcee, la structure de son modele est definie par le produit de parametres independants, affectes d’une dispersion specifique. L’incertitude de la constante de temps thermique resulte de la propagation a travers ce modele des incertitudes parametriques. Nous proposons d’estimer analytiquement cette incertitude en utilisant des distributions parametriques adaptees a la structure multiplicative du modele. La methodologie est illustree par une application numerique concernant les deux cas de transfert convectif.

Light transmission measurements performed in SF6 close to its liquid–gas critical point are used to obtain turbidity data in the reduced temperature range $${\frac{T-T_{\rm c}}{T_{\rm c}}=[1.6\times10^{-7}{-}1.6\times10^{-3}]}$$ (T is temperature, T c is the critical temperature). Automatic experiments (ALICE 2 facility) were made at a near critical density, i.e., $${\frac{\left\langle \rho\right\rangle -\rho_{\rm c}}{\rho_{\rm c}}=0.8\,\%}$$ , in the one-phase homogeneous region, under the microgravity environment of the Mir Space Station ( $${\left\langle \rho\right\rangle}$$ is the average density, ρ c is the critical density). The turbidity data analysis verifies the theoretical crossover formulations for the isothermal compressibility $${\kappa_{T}}$$ and the correlation length ξ. These latter formulations are also used to analyze very near T c thermal diffusivity data obtained under microgravity conditions by Wilkinson et al. (Phys. Rev. E 57 436, 1998).

Effective monitoring and control strategies are essential to maintaining efficient turbine-generator operation. This paper outlines an approach to achieving this aim by integrating a number of artificial intelligence (AI) techniques. An integrated architecture is described and two case studies are presented which demonstrate the potential of utilising such an approach. The paper concludes with a discussion of issues crucial to the further application of AI techniques to turbine-generator monitoring and control.

One of the requirements of diagnostic expert systems is the provision of an explanation of what they are doing and how they reach particular conclusions. This requires knowledge of the user in order to match his/her understanding, and also to be able to justify themselves like human experts do. When they are not understood, they should find alternative ways of explaining. This cannot readily be achieved by a single reasoning paradigm. The research reported in the paper deals with aspects such as multiple models and explanation. In fact, artificial intelligence (AI) paradigms such as rule, model or case based reasoning, have to work together. A general framework is proposed which includes different reasoning agents (e.g. model based reasoning (MBR), case based reasoning (CBR), rule-based systems (IKBS)), a control agent (Control), an explanation module (Explain), a Blackboard (BB) for exchanging and recording messages, and interfaces to domain libraries (Knowledge Bases (KB) e.g. models, cases, rules, etc.), databases (DB) (data from acquisition systems) and a user.

Heuristic based expert systems have difficulty in providing comprehensive solutions to their end users. At the rule level, the knowledge is implicit and therefore can be difficult to justify. Such systems are accurate and efficient, but do not always provide comprehensive solutions. The use of case studies was therefore investigated alongside fault models, both of which are capable of providing solutions acceptable to end users. The research then lead to the design of a second generation expert system, where different knowledge sources (i.e. heuristics, models and cases) can support each others, or can be combined to produce a diagnosis which will still be accurate, but will gain in performance and comprehension. This paper discusses such ideas where case based reasoning can be at the core of the system.

Progress in the knowledge of the water saturation curve is required to improve the accuracy of the calibrations in humidity. In order to achieve this objective, the LNE-CETIAT and the LNE-CNAM have jointly built a facility dedicated to the measurement of the saturation vapor pressure and temperature of pure water. The principle is based on a static measurement of the pressure and the temperature of pure water in a closed, temperature-controlled thermostat, conceived like a quasi-adiabatic calorimeter. A copper cell containing pure water is placed inside a temperature-controlled copper shield, which is mounted in a vacuum-tight stainless steel vessel immersed in a thermostated bath. The temperature of the cell is measured with capsule-type standard platinum resistance thermometers, calibrated with uncertainties below the millikelvin. The vapor pressure is measured by calibrated pressure sensors connected to the cell through a pressure tube whose temperature is monitored at several points. The pressure gauges are installed in a thermostatic apparatus ensuring high stability of the pressure measurement and avoiding any condensation in the tubes. Thanks to the employment of several technical solutions, the thermal contribution to the overall uncertainty budget is reduced, and the remaining major part is mainly due to pressure measurements. This paper presents a full description of this facility and the preliminary results obtained for its characterization.