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Page 728 of 977 Results 7271 - 7280 of 9762

Wang Jian, Yao Hong, Zhang Yue, Cai Changqing, Ding Jingan
INVESTIGATION OF INFLUENCE QUANTITY FOR READING STABILITY ON MAGNETIC SUSCEPTOMETER

According to the measurement principle of weight magnetic parameter, the influence of reading stability for measuring magnetism is analyzed, and the key influence of reading stability is presented in the measurement process. The magnetism of weight is measured by the magnetic susceptometer with capacity of 5.1g and resolution of 0.1 g. At the same time the change of environmental vibration at the laboratory and the fluctuating of ambient magnetic field are measured respectively. The experimental results show the fluctuating of ambient magnetic field that is the key influence of weight magnetism measurement.

Eric Benoit
PROPERTIES OF FUZZY NOMINAL SCALES

Fuzzy nominal scales were introduced in order to propose a formalism to the representation of empirical quantities by fuzzy subsets of words. The purpose of this paper is to explore the possible relations and operators that can be used on measurements performed with this kind of scale. Then an extension of these scales, named fuzzy metric scale, and based on the definition of a distance between measured values is given. As examples of operators, a medium operator and a median filter are given. Finally a comparison procedure of 2 fuzzy metric scale is given.

Paulo R G Couto, Jailton C Damasceno, Luiz Henrique Paraguassú de Oliveira, Jackson S. Oliveira
COMPARATIVE ANALYSIS OF THE MEASUREMENT UNCERTAINTY OF THE DEFORMATION COEFFICIENT OF A PRESSURE BALANCE USING THE GUM APPROACH AND MONTE CARLO SIMULATION METHODS

Uncertainty estimation results are presented for the intercept and slope of the deformation coefficient of a piston-cylinder set of a Budenberg pressure balance operating in the range of 16100 psi (111 MPa) by using the GUM approach and Monte Carlo simulation methods. A study of the influence of the correlation between quantities that define the deformation coefficient on the value of its uncertainty is shown. Monte Carlo simulations are done by using the commercial software Crystal Ball®.

T. Ferreira da Silva, I. B. Couceiro, H. P. H. Grieneisen, Jean Pierre von der Weid
TOWARDS THE IMPLEMENTATION OF A SINGLE-PHOTON DETECTOR ABSOLUTE CALIBRATION SYSTEM WITH CORRELATED PHOTON-PAIRS

An experimental system using correlated photon pairs for absolute measurements of single-photon detectors quantum efficiency has been set up at the Brazilian National Institute of Metrology (INMETRO). The establishment of this methodology is of special significance for the absolute calibration of detectors, especially for near infrared range as an alternative to the conventional radiometric methods. This paper describes the preliminary implementation of this absolute calibration method. Our first experimental results are reported and the optimization of the system is pointed out for obtaining further improvements the near future.

Petr Beneš, Miroslav Uher
IDENTIFICATION OF LIQUID BOILING BY ACOUSTIC EMISSION

Comparisons of the acoustic emission signals from the pool and microlayer boiling and water drop evaporation are the aim of the paper. The main relationships, dependences and research results will be presented. The mechanism of acoustic emission generation in liquid boiling and evaporation is discussed. Based on a theoretical analysis, a set of random process characteristics in time and frequency domain has been selected. Their suitability for the description of the dependence of the generated acoustic emission on liquid overheating is verified by experiment. The original arrangement of the experiment enabled us to reach the critical heat flux in liquid boiling in laboratory for different type of vaporization (pool, microlayer, drop) and simultaneously scans acoustic emission with contact and contactless sensors.

Mário Alves, J. M. Dias Pereira, Helena Geirinhas Ramos
CAN PROTOCOL: A LABORATORY PROTOTYPE FOR FIELDBUS APPLICATIONS

An integrated solution based on CAN protocol, for industrial measurements and control, is presented. Main characteristics of CAN protocol are underlined in terms of OSI model taking particular attention to hardware implementation, messages types, collision resolution mechanisms and timing synchronization. The paper also includes references to another high level industrial protocols that use the physical and logical data layers of CAN protocol. Experimental results based on a developed prototype applied to a level control loop system and main protocol characteristics are analyzed.

Nuno B. Brás, P. A. F. Martins, Raul C. Martins, A. Cruz Serra
REQUIREMENTS OF A MECHANICAL POSITIONING SYSTEM FOR BIOLOGICAL IMAGING USING MAGNETIC INDUCTION TOMOGRAPHY

Magnetic Induction Tomography (MIT) is an imaging technique that allows mapping the complex conductivity structure of a body by measuring the magnetic field generated by currents induced within the body. Typically, MIT systems are static since their sensing positions and the angular incidences of the main magnetic field do not change. Recently the authors from IT developed an experimental setup with movable coils and body to increase the number of measurements. In this paper, a new moving system of sensing coils and body plate is analysed and its importance is highlighted. The accuracy and the measurement requirements for the positioning setup are studied, namely the influence of the displacement error on the measured electromotive signal at the sensing coils for each position. Results from the implemented experimental system are reported and its overall importance is highlighted.

Filomena C. Mouro, Sandra C. Calisto, Maria Ascensão Trancoso
EVALUATION OF MEASUREMENT UNCERTAINTY FOR THE MOISTURE AND DRY MATTER MASS FRACTIONS IN INDUSTRIAL RESIDUES AND SLUDGES

Moisture mass fraction, wH2O, and dry matter mass fraction, wDM, are analytical parameters required by environmental European regulations. The metrological quality, namely measurement uncertainty, comply the fitness for purpose and enhances the comparability of analytical results. In this work, the component by component approach for measurement uncertainty estimation of wH2O and wDM is reported and the input quantities assessed. The measurement uncertainty of method’s precision, under within-laboratory reproducibility conditions, f(precision)Rw, was the only significant influence quantity when wH2O > 0,10 g g-1 for both ranges. In case of wH2O = 0,10 g g-1, the mass of the capsule containing sample after the drying step, m(C+S)dry, has also a relevant contribution. Simplified models are proposed.

Samuel E. de Lucena
PORTABLE MP3 PLAYER AS LOW-COST DATA LOGGER

Non-audio signals have been recorded in the flash ROM memory of a portable MP3 player, in WAV format file, to examine the possibility of using these cheap and small instruments as general-purpose portable data loggers. A 1200-Hz FM carrier modulated by the non-audio signal has replaced the microphone signal, while using the REC operating mode of the MP3 player, which triggers the voice recording function. The signal recovery was carried out by a PLL-based FM demodulator whose input is the FM signal captured in the coil leads of the MP3 player's earphone. Sinusoidal and electrocardiogram signals have been used in the system evaluation. Although the quality of low frequency signals needs improvement, overall the results indicate the viability of the proposal. Suggestions are made for improvements and extensions of the work.

A. Bounouh, F. Blard, H. Camon, D. Bélières, F. Ziadé
MICROSYSTEMS FOR ELECTRICAL AC VOLTAGE METROLOGY

In the framework of developing MEMS devices to fabricate AC voltage references for electrical metrology and high precision instrumentation, several first devices have been designed and fabricated using a Silicon On Insulator (SOI) Surface Micromachining process. The measured MEMS AC voltage reference values have been found to be from 5 V to 100 V in a good agreement with the calculated values performed with Coventor and Comsol finite elements software. Second set of devices with improved characteristics has also been fabricated. The stability of the MEMS out-put voltage at 100 kHz has been found very promising for the best samples where the relative deviation from the mean value over almost 12 hours showed a standard deviation of about 6.3 ppm.

Page 728 of 977 Results 7271 - 7280 of 9762