(Calib.) Artículos

URI permanente para esta colecciónhttps://digitalpro.inta.es/handle/20.500.12666/65

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A simple geometrical model for calculation of the effective emissivity in blackbody cylindrical cavities
(Springer Link, 2015-10-15) de Lucas Veguillas, Javier; Instituto Nacional de Técnica Aeroespacial (INTA)
A simple geometrical model for calculating the effective emissivity in blackbody cylindrical cavities has been developed. The back ray tracing technique and the Monte Carlo method have been employed, making use of a suitable set of coordinates and auxiliary planes. In these planes, the trajectories of individual photons in the successive reflections between the cavity points are followed in detail. The theoretical model is implemented by using simple numerical tools, programmed in Microsoft Visual Basic for Application and Excel. The algorithm is applied to isothermal and non-isothermal diffuse cylindrical cavities with a lid; however, the basic geometrical structure can be generalized to a cylindro-conical shape and specular reflection. Additionally, the numerical algorithm and the program source code can be used, with minor changes, for determining the distribution of the cavity points, where photon absorption takes place. This distribution could be applied to the study of the influence of thermal gradients on the effective emissivity profiles, for example. Validation is performed by analyzing the convergence of the Monte Carlo method as a function of the number of trials and by comparison with published results of different authors.
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A subcell FDTD Scheme implementation for thin slot modeling
(Institute of Electrical and Electronics Engineers, 2022-07-08) Cabello, M. R.; Martín Valverde, A. J.; Plaza Gallardo, Borja; Frövel, Malte; Poyatos Martinez, David; Rubio Bretones, Amelia; González García, S.; Instituto Nacional de Técnica Aeroespacial (INTA); Ministerio de Ciencia e Innovación (MICINN); Agencia Estatal de Investigación (AEI); Junta de Andalucía
The finite-difference time-domain (FDTD) method is not able to efficiently model thin features without a drastic reductions of the spatial mesh size, potentially yielding an unfeasible use of memory and CPU requirements. In this work we propose two stable and efficient techniques for dealing with thin apertures in FDTD, one based on conformal and one based on subgridding. These are compared, in two different scenarios, with the classical dispersive magnetic material approximation [DMMA] based on Gilbert-Holland's models.
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An investigation of the comparative performance of diverse humidity sensing techniques in natural gas
(Elsevier, 2015-02-21) García Gallegos, Jaime; Benyon Puig, Robert; Ávila, Sara; Benito, Angel M.; Gavioso, Roberto Maria; Mitter, Helmut; Bell, Stephanie; Stevens, Mark; Böse, Norbert; Ebert, Volker; Heinonen, M.; Peruzzi, Andrea; Bosma, Rien; Val´ková, Miroslava
Moisture content is a key factor regardless of the activity carried out inside the natural gas industry (production, processing, transmission, etc.). Not only does the efficiency of the final product, known as heating value, decrease when the water content is high, but it can also trigger potentially dangerous conditions due to the formation of hydrates, that can block pipelines and damage pumping devices and produce other negative effects. For these reasons, accurate measurement and control of humidity is absolutely essential. However, current practice for such moisture measurements is for the devices to be calibrated at atmospheric pressure and in nitrogen or air as the matrix gas, conditions that vary significantly from those present in the actual industrial process. For that, eleven hygrometers based on different measurement principles (chilled-mirror, electrolytic sensor, a spectroscopic analyzer, polymeric and metal oxide humidity sensors) have been compared at facilities of the main carrier of natural gas in Spain, using natural gas at absolute pressures between 0.1 MPa and 6 MPa, and for a range of water content from 13 ppmv to 250 ppmv. Their relative performance is described in terms of the response times, long term stability, hysteresis and behaviour under large pressure changes. Most instruments, exceptions are detailed in the article, show good behaviour regarding response time, hysteresis and under sudden pressure changes. In contrast, drift can be identified in most of the aluminium oxide probes tested.
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Aperturas efectivas en calibración y comparación de termómetros de radiación
(Federación de Asociaciones de Ingenieros Industriales de España, 2020-09-15) de Lucas Veguillas, Javier; Instituto Nacional de Técnica Aeroespacial (INTA)
Los termómetros de radiación (TR) se calibran con cuerpos negros (CN) cuya apertura debe cubrir suficientemente el blanco nominal del termómetro. Debido a posibles imperfecciones en su sistema óptico, radiación proveniente de regiones exteriores al blanco puede llegar al detector. Es el efecto del tamaño de la fuente (ETF) y constituye una limitación importante en el uso de TR en aplicaciones especialmente en un entorno industrial y fuente entre otras de incertidumbre de medida.
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Characterization of absolute cavity radiometers for traceability to SI of solar irradiance
(IOP Science Publishing, 2022-08-12) Balenzategui, José Lorenzo; de Lucas Veguillas, Javier; Cuenca, José; González Leiton, Ana María; Molero García, María; Fabero, Fernando; Silva, José Pedro; Mejuto, Eduardo; Muñoz, R.; Arce, A.; Instituto Nacional de Técnica Aeroespacial (INTA)
Solar-type cavity radiometers are instruments of the highest metrological level for measuring solar direct normal irradiance. To ensure their traceability and performance, they are periodically compared to the World Group of Standards, which realizes the World Radiometric Reference (WRR), in the International Pyrheliometer Comparisons (IPCs). Additionally, they can be characterized in an absolute way, with direct traceability to SI units and with their measurement uncertainty calculated. This paper describes the different techniques and procedures applied for the characterization and calibration of solar cavity radiometers, with the main results obtained to date in the case of an Automatic Hickey–Frieden (AHF) radiometer. Voltmeters, resistors, temperature sensors and the area of the precision apertures have been calibrated, while the effective absorptance, temperature coefficients, optical scattering and non-equivalence factor have been evaluated. The temperature dependence of the electrical current in the cavity heater has also been analysed. The resulting corrections obtained for the AHF by characterization are compatible with the WRR factors obtained by this instrument in the past IPCs. An uncertainty of 0.42% (k = 1) has been obtained, and this paper discusses further improvements that may be able to reduce this figure to the desired expanded uncertainty of U = 0.1% (k = 2).
Acceso Abierto
Comparison in humidity (dew-point temperature high range) dew point temperature +30 °C to 95 °C
(IOP Science, 2024-12-18) Deschermeier, Regina; Bell, Stephanie; Benyon Puig, Robert; Bonde Kentved, Anders; Carroll, Paul; Fernicola, Vito; García Gallegos, Jaime; Heinonen, Martti; Hudolkin, Domen; Jarosz, Rafal; Kokkini, Evmorfia; Mac Lochlainn, Dubhaltach; Mitter, Helmut; Aytekin, Seda Oğuz; Panman, Matthijs; Senn, Remo; Šestan, Danijel; Smorgon, Denis; Stevens, Mark; Zvizdić, Davor
The report summarises the results of the EURAMET.T-K8 key comparison (EURAMET Project No. P 717) in the field of humidity. The comparison covers the dew-point temperature range from +30 °C up to + 95 °C dew point temperature. The report gives details of the scheme, procedure and analysis of the comparison. The overall results display a very good agreement of the 16 participating laboratories. The two dew-point hygrometers used as travelling standard were sufficiently stable. The linkage to the corresponding CCT-K8 comparison will be calculated when the final results for both comparisons are available. Possible procedures are described in the text. In the conclusion, some remarks for improvement for future RMO key comparisons are given.
Acceso Abierto
Constraints on the Spatial Distribution of Lunar Crustal Magnetic Sources From Orbital Magnetic Field Data
(Advancing Earth and Space Science (AGU), 2024-02-14) Oliveira, Joana S.; Vervelidou, Foteini; Wieczorek, Mark A.; Díaz Michelena, Marina; Ministerio de Ciencia e Innovación (MICINN); European Research Council (ERC)
Spacecraft measurements show that the crust of the Moon is heterogeneously magnetized. The sources of these magnetic anomalies are yet not fully understood, with most not being related to known geological structures or processes. Here, we use an inversion methodology that relies on the assumption of unidirectional magnetization, commonly referred to as Parker's method, to elucidate the origin of the magnetic sources by constraining the location and geometry of the underlying magnetization. This method has been used previously to infer the direction of the underlying magnetization but it has not been tested as to whether it can infer the geometry of the source. The performance of the method is here assessed by conducting a variety of tests, using synthetic magnetized bodies of different geometries mimicking the main geological structures potentially magnetized within the lunar crust. Results from our tests show that this method successfully localizes and delineates the two-dimensional surface projection of subsurface three-dimensional magnetized bodies, provided their magnetization is close to unidirectional and the magnetic field data are of sufficient spatial resolution and reasonable signal-to-noise ratio. We applied this inversion method to two different lunar magnetic anomalies, the Mendel-Rydberg impact basin and the Reiner Gamma swirl. For Mendel-Rydberg, our analysis shows that the strongest magnetic sources are located within the basin's inner ring, whereas for Reiner Gamma, the strongest magnetic sources form a narrow dike-like body that emanates from the center of the Marius Hills volcanic complex.
Acceso Abierto
Digital transformation: Ensuring metrological traceability
(Elsevier, 2024-12-27) Benyon Puig, Robert; García Gallegos, Jaime; Mohíno Herranz, Inmaculada; Perez Sanz, Fernando; Vicente Mussons, Tomás
The digital transformation project for the calibration and testing laboratories of INTA is presented. It is intended to serve as the institute's single platform for integrating knowledge, capabilities and innovative metrology techniques, quality and testing systems, to produce highly efficient and reliable results while ensuring metrological traceability of R + D + i results. It provides the necessary data for decision support and aims to address many current issues faced by laboratories and testing centres. The project is developed across the following action areas: (a) Automation of quality assurance for measurements according to ISO/IEC 17043 standard; (b) Automation of data capture and analysis of calibration procedures for the Metrology and Calibration Centre (CMC) and various tests; (c) Digital services for remote auditing of measurement and testing services in accordance with ISO/IEC 17025 and ISO/IEC 17043 standards; (d) Evolution towards the flexibility and expansion of parameterization of the different modules to facilitate implementation in any type of INTA and Ministry of Defence (MoD) laboratories.
Acceso Abierto
Digitalization of a calibration laboratory: Batch calibration
(Elsevier, 2024-12-22) Perez Sanz, Fernando; Larroca Sanz, Rebeca; Mohíno Herranz, Inmaculada; García Gallegos, Jaime; Vicente Mussons, Tomás; Benyon Puig, Robert
The Metrology and Calibration Centre (CMC) at the National Institute of Aerospace Technology (INTA) has introduced an innovative tool designed to enhance the efficiency and effectiveness of calibration processes within its facilities. This cutting-edge software enables technicians to conduct multiple calibrations simultaneously, provided the requisite experimental setup is in place. Developed with a focus on streamlining the entire calibration workflow, from data acquisition to certificate issuance, the software ensures compliance with the ISO/IEC 17025 standard. Through rigorous testing, the CMC verified the software's performance using devices employed for monitoring ambient conditions (temperature and humidity) across various INTA test laboratories. Notably, these devices underwent batch calibration in groups of six, resulting in a sixfold reduction in experimentation time. Although the associated paperwork was reduced, the necessity to maintain traceability and issue individual calibration certificates for each device offsets the time savings.
Acceso Abierto
Digitalization of on-site characterization of climatic chambers
(Elsevier, 2024-12-27) García Gallegos, Jaime; Benyon Puig, Robert; Perez Sanz, Fernando; Mohíno Herranz, Inmaculada; Vicente Mussons, Tomás
The implementation of a software tool applied to the characterization of climatic chambers is presented and discussed. INTA took part in the design and development of the algorithms for the automatic identification of stabilization periods of physical parameters measured based on defined acceptance criteria and the application of mathematical and statistical analysis for the interpretation of the results obtained. The new operational procedure implemented at INTA is presented as an innovation in the service offered by the laboratory to its clients, allowing them to improve the efficiency of their production processes. It enables the remote calibration of climatic chambers and other thermal facilities of the Institute in different locations in Spain, without the need to move calibration technicians, resulting in increased efficiency in the use of human resources and cost savings.
Restringido
Evaluation of a Portable Apparatus for the Realization of the Triple Point of Argon
(Springer Link, 2014-06-21) de Lucas Veguillas, Javier; Benyon Puig, Robert
In this paper, the evaluation of the performance of a portable triple-point-of-argon apparatus, via the analysis of the calibration history of selected working (fused silica) standard platinum resistance thermometers (SPRTs), is presented. These have an extensive calibration history, both internally (using different apparatus) and externally at two National Measurement Institutes. A special procedure had to be developed, for the calibration of metal-sheathed SPRTs, in order to ensure adequate thermal contact between the SPRT and the well and to minimize the influence of stem conduction, inherent in the compact design of the maintenance system. The results show good agreement between the measurements performed with this system and those with the previously used apparatus, to a level of uncertainty consistent with the INTA calibration and measurement capability (CMC) of 3.0 mK (k = 2). This CMC is given by the Spanish accreditation body (ENAC), under accreditation No. 16/10.007, for the routine calibration of SPRTs at the triple point of argon. It is concluded that the portable apparatus is suitable for use as a transfer standard for the comparison of local realizations of the triple point of argon. This avoids the need to shipping fragile SPRTs, with a valuable long calibration history, and eliminates the contributions due the long-term stability of the thermometers subjected to transportation. The long-term stability of the portable apparatus reported in this work has only been determined in laboratory conditions.
Restringido
Experimental evaluation of the performance of humidity analyzers in natural gas under industrial conditions
(Elsevier, 2016-03-03) García Gallegos, Jaime; Ávila, Susana; Benyon Puig, Robert; McKeogh, G.; Stokes, Andrew
The work reported is the continuation of the extensive comparison performed in controlled laboratory conditions using natural gas from the Spanish grid, as part of the European Metrology Research Project (EMRP) “Characterisation of Energy Gases” (ENG01-Gas, 2009). One of the outcomes of the project was the good performance of a laser absorption spectrometer with respect to other measurement technologies, in particular the absence of appreciable drift effects, exhibited by aluminium oxide (Al2O3) sensors that are traditionally used in the natural gas industry. The investigation was performed over a wide range of humidity content (13 ppmv to 250 ppmv) in ambient conditions of 23 °C ± 3 °C, at Enagás central laboratory in Zaragoza, Spain (Gallegos et al., 2015). We report the subsequent comparison of two laser absorption analyzers, from different manufacturers, and a conventional Al2O3 installed on site in real industrial conditions, at an underground gas storage (UGS) and drying plant of Enagás in Serrablo, Spain. The performance of sensors is reported and discussed for all production stages of the plant (extraction, injection and shutdown), during which extreme ambient temperature values took place (from −15 °C up to 40 °C) and at line pressures up to 6.7 MPa. A purpose built sampling system was designed and constructed to accommodate the different instrumentation requirements and ensure an optimum metrological analysis. The new results are compared with those previously obtained under more ideal laboratory conditions in the context assuring compliance with the contractual specifications that are to be met in Europe (EASEE-gas, 2005).
Acceso Abierto
Final report to the CCT on key comparison CCT-K8 - comparison of local realisations of dew-point temperature of humid gas in the range 30 °C to 95 °C
(IOP Science, 2025-02-04) García Gallegos, Jaime; Mitter, Helmut; Abe, Hisashi; Benyon Puig, Robert; Carroll, P.; Choi, B. I.; Deschermeier, Regina; Ebert, V.; Fernicola, Vito; Wang, L.; Meyer, C.; Smorgon, Denis; Vicente Mussons, Tomás
The report summarises the results of the CCT-K8 key comparison in the field of humidity. The main target of this comparison was to obtain the degree of equivalence (DoE) between realizations of local scales of dew point temperature of humid gas (air), in the range from 30 °C to 95 °C, among the participating national metrology institutes. The report gives details of the scheme, procedure and analysis of the comparison. The overall results display a very good agreement of the nine participating laboratories. The results show excellent agreement between the realized scales with no detected outliers. The performance of the travelling standards was excellent and can be attributed to the intensive preconditioning and selection of the platinum resistance thermometers, prior to their integration into the measuring head assembly, that led to insignificant drift. In the conclusion, some lessons learned are reported that could be beneficial for future key comparisons.
Restringido
Geometrical and thermal optimization of cylinder-conical blackbody cavities to uniform radiance temperature profiles in the infrared
(Elsevier, 2023-04-07) de Lucas Veguillas, Javier; Segovia, José Juan; Instituto Nacional de Técnica Aeroespacial (INTA)
Large-area blackbody cylinder conical cavities are generally used as primary radiation sources for calibrating and characterizing radiation thermometers and quantitative thermal imagers in the infrared, both in metrology laboratories or for industrial applications. The radiation temperature of the emitted radiation depends on effective emissivity and surface (contact) temperature. The instrument’s field of view generally only covers the cavity bottom since this is where contact temperature is best measured. A non-uniform effective emissivity profile at the bottom poses a problem if instruments with a different field of view have to be calibrated with the same blackbody. Spatial uniformity depends principally on the cone angle and temperature gradient along the cavity. In this paper, we analyse blackbody optimization in terms of uniform radiance temperature profiles as a function on geometric parameters and temperature. For the isothermal case, we conclude that angles between 160° and 170° are the optimum, depending on intrinsic emissivity and length-to-diameter ratio of the cavity. For non-isothermal cavities, the effect of the temperature gradient on uniformity is relatively small, with only the temperature near the bottom proving significant. The use of multi-zone maintenance furnaces would allow temperature gradients to be designed that can improve uniformity in addition to geometric optimization.
Acceso Abierto
Implementing transfer learning for sound event classification using the realised audio database
(Elsevier, 2025-01-04) Mohíno Herranz, Inmaculada; García Gómez, Joaquín; Alonso Díaz, Sagrario; García Gallegos, Jaime; Perez Sanz, Fernando; Aguilar Ortega, Miguel; Gil Pita, Roberto; Agencia Estatal de Investigación (España); Comunidad de Madrid
Currently, smart spaces utilize diverse sensors to gather real-time data on activities within environments, enabling systems to activate alarms or execute tasks. These environments support various applications integrating advanced sensory systems like cameras, microphones, and motion sensors. Acoustic sensors are crucial, extracting valuable information from sound waves, including source details and environment characteristics. This article focuses on detecting and classifying common household sounds using the ReaLISED database, comprising 2479 recordings of 18 events. Audio data were collected in real homes with everyday objects and activities, unlike reverberation models. Artificial Intelligence techniques, including Machine Learning classifiers, yielded satisfactory outcomes. Transfer Learning methods were explored, leveraging pre-trained models like YAMNet for sound event recognition by Google, potentially outperforming previous classifiers. Preliminary results reveal a relative reduction of around 25 % in the probability error rate when comparing the obtained results with previous studies, providing valuable insights into potential possibilities and enhancements.
Acceso Abierto
In-flight calibration of the MEDA-TIRS instrument onboard NASA's Mars2020 mission
(Elsevier, 2024-11-09) Sebastián, E.; Martínez, Germán M.; Ramos, Miguel; Smith, Michael D.; Peinado, V.; Mora Sotomayor, L.; Lemmon, M. T.; Vicente Retortillo, Álvaro; de Lucas Veguillas, Javier; Ferrándiz, Ricardo; Rodríguez Manfredi, J. A.
This article describes a novel procedure and algorithm used for the in-flight calibration of the Thermal Infrared Sensor (TIRS) onboard the Mars 2020 mission. The purpose is to recalibrate the responsivity of TIRS’ IR detectors as they degrade following surface operations and exposure to harsh environmental conditions. Using data from in-flight calibration campaigns conducted through sol 800 of this mission, we report the time evolution of the responsivity for the different IR detectors, as well as the final performance achieved by the algorithm in the real operating environment. Moreover, we analyzed changes in responsivity as a function of TIRS geometric design and environmental factors, e.g., detector orientation, direct exposure to prevailing winds and solar radiation, electrostatic properties of the detector filter, and atmospheric dust concentration. We concluded that dust deposition on the detectors' filter during landing, and later during operation is the most likely cause of the degradation observed in the various channels, with gravitational sedimentation and the capacity of the filters to accumulate electrostatic charge being key factors. The relative and absolute degradation of the TIRS is similar to those reported by other Martian missions and instruments with similar orientations, and to date, it has shown no signs of cleaning after more than a year on the surface of Mars. Accounting for changes in responsivity during the mission is critical to maintaining the reliability of TIRS measurements, which will later be made available in NASA's Planetary Data System for the benefit of the scientific community.
Acceso Abierto
Investigación del efecto del tamaño de la fuente en equipos de termografía infrarroja y termómetros de radiación
(Gobierno de España: Ministerio de Defensa, 2018-10-03) de Lucas Veguillas, Javier; Alonso, S.; Bernal, M.; Ángeles Sierra, M.; Macías, R.
Las cámaras y los sistemas de termografía infrarroja son utilizados en múltiples aplicaciones en sectores de seguridad y defensa: optrónica, sensores, contrame didas, estudio termográfico del estrés del combatiente, etc. Su evolución ha sido espectacular, especialmente desde la introducción del microbolómetro como detector elemental. En el pasado se utilizaban básicamente para medidas cualitativas, interesando únicamente el contraste térmico, la búsqueda de puntos calientes o fugas de calor, etc. Hoy son más las aplicaciones cuantitativas, combinando la imagen térmica con medidas absolutas de temperatura. La necesidad de garanti zar la trazabilidad al SI de los valores de temperatura proporcionados exige a los laboratorios de calibración investigar los factores de influencia que afectan a los resultados de las medidas realizadas. La incertidumbre en la medida depende de multitud de factores (por ejemplo, la emisividad) y uno de los más significativos es el efecto del tamaño de la fuente (ETF), por el cual, debido a imperfecciones en el sistema óptico (difracción, reflexiones internas, etc.), radiación proveniente de zonas fuera del blanco correspondiente a un píxel pueden llegar a este. En termografía se habla del efecto sobre la temperatura indicada por el píxel y de valores leídos por detectores vecinos. Es equivalente a considerar que el tamaño de la fuente incide en el valor de temperatura que proporciona un termómetro de radiación. El laboratorio de Temperatura y Humedad del INTA (Instituto Nacional de Técnica Aeroespacial) tiene acreditación ENAC (Entidad Nacional de Acreditación) para la calibración de termómetros de radiación y la indicación de temperatura de cámaras termográficas, y actúa en este ámbito como laboratorio metrológico del Ministerio de Defensa. En este trabajo se presentan resultados de la investigación realizada sobre el ETF y se analiza su influencia en la incertidumbre y sobre los valores de temperatura proporcionados por estos instrumentos.
Restringido
Measurement and analysis of the temperature gradient of blackbody cavities, for use in radiation thermometry
(Springer Link, 2018-03-24) de Lucas Veguillas, Javier; Segovia, José Juan; Instituto Nacional de Técnica Aeroespacial (INTA)
Blackbody cavities are the standard radiation sources widely used in the fields of radiometry and radiation thermometry. Its effective emissivity and uncertainty depend to a large extent on the temperature gradient. An experimental procedure based on the radiometric method for measuring the gradient is followed. Results are applied to particular blackbody configurations where gradients can be thermometrically estimated by contact thermometers and where the relationship between both basic methods can be established. The proposed procedure may be applied to commercial blackbodies if they are modified allowing secondary contact temperature measurement. In addition, the established systematic may be incorporated as part of the actions for quality assurance in routine calibrations of radiation thermometers, by using the secondary contact temperature measurement for detecting departures from the real radiometrically obtained gradient and the effect on the uncertainty. On the other hand, a theoretical model is proposed to evaluate the effect of temperature variations on effective emissivity and associated uncertainty. This model is based on a gradient sample chosen following plausible criteria. The model is consistent with the Monte Carlo method for calculating the uncertainty of effective emissivity and complements others published in the literature where uncertainty is calculated taking into account only geometrical variables and intrinsic emissivity. The mathematical model and experimental procedure are applied and validated using a commercial type three-zone furnace, with a blackbody cavity modified to enable a secondary contact temperature measurement, in the range between 400 °C and 1000 °C.
Acceso Abierto
Measurement, Validation and Uncertainty of an Experimental Procedure to Characterize the Size-of-Source Effect of Radiation Thermometers, in the Framework of an Industrial Calibration Laboratory
(Multidisciplinary Digital Publishing Institute (MDPI), 2022-10-28) de Lucas Veguillas, Javier; Instituto Nacional de Técnica Aeroespacial (INTA)
An experimental procedure for characterizing the size-of-source effect (SSE) is proposed. Such an effect is the cause of one of the main influence variables generating uncertainty in the measurement, both in calibration and use, of direct reading radiation thermometers (RT). The procedure and uncertainty calculation described in the paper are aligned in terms of metrological traceability, with the requirements generally imposed to ensure the accuracy of measurements in industry and science. Results of application and validation of this particular procedure with equipment, including black body (BB) sources normally used in radiation thermometry calibration laboratories in the industrial field, are shown.
Restringido
Measuring Humidity in Methane and Natural Gas with a Microwave Technique
(Springer Nature Link, 2014-03-01) Gavioso, R. M.; Madonna Ripa, D.; Benyon Puig, Robert; García Gallegos, Jaime; Pérez-Sanz, F.; Corbellini, S.; Ávila, S.; Benito, A. M.
The results of microwave measurements with a quasi-spherical resonator in humid methane samples realized under laboratory conditions at the Istituto Nazionale di Ricerca Metrologica (INRiM) and under industrial conditions in a natural gas sample made available at the facilities of the Technical Manager of the Spanish Gas System and main supplier of natural gas in Spain (ENAGAS) are reported. Measurements at INRiM included vapor phase and condensation tests on methane samples prepared with amount fractions of water between 600 ppm and 5000 ppm at temperatures between 273 K and 295 K and pressures between 150 kPa and 1 MPa. ENAGAS measurements were performed at ambient temperature, 750 kPa on natural gas sampled from the pipeline and successively humidified at amount fractions of water between 140 ppm and 250 ppm for completeness of the comparison with several humidity sensors and instrumentation based on different technologies. To enhance the sensitivity of the microwave method at low humidity, an experimental procedure based on the relative comparison of the dielectric permittivity of the humid gas sample before and after being subject to a chemical drying process was conceived and implemented. The uncertainty budget and the final sensitivity of this procedure are discussed.

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