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Page 737 of 977 Results 7361 - 7370 of 9762

Gonçalo Baptista, Florbela A. Dias, Eduarda Filipe
ETHANOL PRIMARY GAS STANDARDS PREPARATION

In this paper it will be discussed the gravimetric method to produce ethanol primary gas standards according to the international standard ISO6142.
The ethanol gas standards are prepared by vaporizing ethanol in nitrogen and compressing them in a pressurized cylinder. During the preparation process careful control of weighing and all parameters that can influence it, such as air temperature, pressure and humidity, shall be made.
The standards composition are further analysed by the analytical method non dispersive infrared spectroscopy (NDIR). The traceability is assured comparing the composition with national standards of mass, pressure, temperature and other national/international amount of substance standards.

Aleksandar Nikolic, Ilija Stevanovic
POWER QUALITY MEASUREMENT ANALYSIS OF THE ELECTROSTATIC PRECIPITATOR

Power quality measurement analysis of the electrostatic precipitator in thermal power plant under different working conditions is presented in the paper. Control of electrostatic precipitator is realized by digitally controlled antiparallel thyristors. In the first regime (continual) the constant firing angle of thyristor is set in dependence of the reference current. In other regime (intermittent) the ON/OFF period is set. For both control strategies the measurement of the content of higher harmonic of voltage and current is performed. Analysis of the measured results is done according to the methodology based on EU power quality standard EN 50160. The plant under investigation is electrostatic precipitator in the largest thermal power plant "Nikola Tesla A" in Serbia, but the obtained results could be used for any similar power plant.

Jerzy Sladek, Marcin Krawczyk
MATRIX METHOD FOR LCMM — CONNECTION BETWEEN SUBSPACES OF REFERENCE POINTS

The article describes the transplantation of Matrix Method as an assessment of accuracy of coordinate measurement for Large CMM. The method of the synthetic description of the accuracy is used successfully for small and medium-sized CMMs. It is implemented for large measurements as research project nr: PB 5T07/D03824. The issue involves many problems, especially from a technical point of view. This article presents experiments concerning connections between reference subspaces – the crucial elements for implementation of Matrix Method.

Francesco Crenna, Giovanni Battista Rossi, Luca Bovio
MEASUREMENT SET UP FOR THE EXPERIMENTAL STUDY OF THE DYNAMICS OF HOPPING

Hopping is a gesture that, though simple, is apt to providing precious information on human-body dynamics, including dynamic stability. Currently available studies are normally based on a limited set of sensors and scarcely provide metrological details. This paper presents a new multi-sensors measurement set-up, including acceleration, force, angles and image-based positions. The metrological characteristics of the system are discussed, including systematic and random uncertainty contributions, measurement conditions and procedure. The same experimental apparatus may be used for studying other motion gestures, such as stepping down, forced hopping or cycling, thus providing a flexible experimental tool.

Francesco Crenna, Giovanni Battista Rossi
MEASUREMENTS FOR THE EVALUATION OF VIBRATION EXPOSURE OF OPERATORS IN A SHIP CONTAINER TERMINAL

The measurement of the vibration transmitted to the human body is key for the prevention of the risk of spine damage, in the long run, for operators of industrial vehicles. Even if no such risk exists, such information is important for assessing the comfort and, consequently, for ensuring proper ergonomic conditions. In this paper we discuss important issues concerning the measurement of vibrations transmitted to operators by vehicles used for moving and handling containers in a maritime terminal. Sensor installation is considered, with particular attention to interfacing problems, proposals for improving the reliability of the measured values are presented and factors influencing the variability of measurement results are analysed. Lastly, experimental results are presented and discussed, with particular attention to characterising parameters used for exposure evaluation.

Enrico Marcuzzi, Giorgio Parzianello, Massimiliano Tordi, Massimo Bartolozzi, Massimo Lunardelli, Antonio Selmo, Luca Baglivo, Stefano Debei, Mariolino De Cecco
EXTRINSIC PARAMETERS CALIBRATION OF A STRUCTURED LIGHT SYSTEM VIA PLANAR HOMOGRAPHY BASED ON A REFERENCE SOLID

Structured light systems are widely used for three-dimensional shape reconstruction. The accuracy of the vision system parameters is of paramount importance for the accuracy of the 3D reconstruction. Often the extrinsic parameters change over time due to environmental conditions, in order to compensate for structured light parameters change, a self-recalibration method based on planar homography is proposed in this paper. The method uses the planar homography of corresponding points in two camera views to identify the relative position and orientation between the two cameras: one is the "real" camera, while the other is a reference solid considered as a "pseudo-camera". The laser plane of the structured light vision system is the constraining plane for the two cameras corresponding points.
In order to assess the metrological quality of the method an evaluation of the accuracy of the 3D reconstruction is performed by a two step Monte Carlo simulation. In a first step it is estimated the extrinsic parameters accuracy obtained by self-recalibration. In a second step the intrinsic parameters accuracy and the extrinsic one previously computed are used to evaluate the accuracy of 3D shape reconstruction. In the final version of the paper, the overall accuracy will be verified experimentally by a proper calibration setup.

M. João Nunes, M.J. Guiomar Lito, M. Filomena Camões, Eduarda Filipe
PORTUGUESE PH INTERLABORATORY COMPARISON

The first interlaboratory comparison at national level for pH measurement of a primary standard phosphate buffer solution was carried out. The main aim of the exercise was to verify the way laboratories are planning and performing pH measurements and evaluates the performance of each laboratory. Seven laboratories have participated in this study.

Vukan Ogrizovic, Violeta Vasilic, Sinisa Delcev, Jelena Gucevic
TESTING THE STABILITY OF GPS OSCILLATORS WITHIN SERBIAN PERMANENT GPS STATIONS NETWORK

Periodic tests of quartz oscillators incorporated in GPS receivers in Serbia are performed in accredited metrological laboratories by the procedure adopted in metrological laboratory ML160. However, receivers of Serbian permanent stations network (AGROS) are permanently mounted on the top of roofs of local cadastral offices, spread along territory of Serbia. They cannot be taken to a metrological laboratory for calibration because of need for constant work. A method for testing their oscillator stability is presented in this paper.

Oliver Mack, Sascha Mäuselein
RECOMMENDED FOR THE REVISION OF TEST PROCEDURES FOR LOAD CELLS IN LEGAL METROLOGY

Load cells (LC) used in weighing instruments under legal control can be tested separately as a module according to the OIML recommendation R60 (R60). R60 prescribes the principle metrological static characteristics and static evaluation procedures for LCs used in weighing instruments for legal metrology. Since the 1st revision of R60 published in 2000 further developments of LCs lead to new experience and requirements.
This paper presents abnormalities of LCs observed on single test patterns like the influence of the force introduction, eccentricity effects, effects of excitation voltage variations, drying effects of the strain gauge sealing but also effects of temperature gradients that may strongly affect the metrological characteristic of LCs.
The effects have to be discussed and taken into account for a planned 2nd revision of R60 if needed.

Tomáš Radil, Pedro M. Ramos, A. Cruz Serra
SINGLE-PHASE POWER QUALITY ANALYZER BASED ON A NEW DETECTION AND CLASSIFICATION ALGORITHM

This paper describes a simple power quality analyzer based on a digital signal processor. In this analyzer, a new algorithm for detection and classification of power quality events is implemented. The analyzer detects and classifies in real-time transients, waveform distortions, sags, interruptions and swells.

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