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R. Afonso, M. Klonz, R. M. Souza, R. P. Landim
INMETRO’S PRIMARY AC-DC CURRENT TRANSFER STANDARD BASED ON PMJTCS

This paper describes the new primary standard for the ac-dc current transfer at Inmetro, based on PMJTCs and the new shunts manufactured by Fluke for rated currents from 10 mA up to 20 A. The build-up of the ac-dc current scale is described together with the uncertainty budgets which result in final uncertainties at 5 A of 6 μA/A to 12 μA/A in the frequency range from 10 Hz to 100 kHz. These are small compared to international standards.

Fernando M. Janeiro, Pedro M. Ramos
IMPEDANCE CIRCUIT IDENTIFICATION THROUGH EVOLUTIONARY ALGORITHMS

Impedance circuit identification through spectroscopy is used to characterize sensors. When the circuit topology is known, genetic algorithms can be used to obtain the circuit component values. Gene expression programming can be used to search for an adequate circuit topology. In this paper, an improved version of the impedance circuit identification based on gene expression programming and hybrid genetic algorithm is presented. Numerical results based on a real sensor are presented.

Pedro E. Xavier, Fernando M. Janeiro, Pedro M. Ramos
EFFICIENT IMPLEMENTATION OF MULTIHARMONIC LEAST-SQUARES FITTING ALGORITHMS

Multiharmonic least-squares fitting algorithms have been applied in many fields of instrumentation and measurement. However, as the number of harmonics increases, the size of the matrices needed to describe the relation between the sampled signal and the multiharmonic model increases substantially. In this paper an efficient memory-wise implementation of the algorithm is proposed, and numerical simulations are used to assess its performance. Measurement results are also presented.

João Claudio D. Carvalho, Marcelo M. Costa, Rafael T. Barros, Thiago B. P. Souza
COMPARISON AMONG THREE DIFFERENT DIGITAL MULTIMETER CALIBRATION METHODOLOGIE

This paper presents the comparison among three methodologies of digital multimeter calibration, two established by Brazilian and international guides, and one developed by the Eletrobras Eletronorte Electrical Calibration Laboratory. In each methodology, aspects as number of calibration points, calibration time and reliability are evaluated.

Gabriel Slomovitz, Daniel Slomovitz
DIGITAL PROCESSING OF IMPULSE MEASUREMENTS IN TRANSFORMER TESTS

Tests using high voltage impulse waveforms are used to evaluate power transformers. This test simulates the overvoltage that may exist during a lighting storm. This paper proposes digital processing of the voltages and currents recorded during the test to evaluate if the transformer under test pass or not the standard requirements.

E. Costa Silva, L. A. P. Gusmão, C. R. Hall Barbosa, E. Costa Monteiro
HOMOGENIZATION OF THE IMPEDANCE PHASE CHARACTERISTICS OF GIANT MAGNETOIMPEDANCE SENSORS

Over the last decade, Giant Magnetoimpedance (GMI) sensors have been intensively studied as a new possibility for measuring ultra-weak magnetic fields. To achieve that goal, the employment and optimization of gradiometric configurations are a key factor, aiming at reducing the magnetic interference. The homogeneity of the impedance characteristics of GMI sensors is strongly related to the performance of the gradiometers. Then, pursuing the development of better gradiometers, this work aims at presenting a new electronic approach developed by our research group, which leads to the homogenization of the phase characteristics of heterogeneous GMI samples and, consequently, can be used toimprove the performance of phase-based GMI magnetometers.

M. Surdu, A. Lameko, A. Labuzov
THE NEW APPROACH TO THE RANGE EXPANDING IN IMPEDANCE MEASUREMENTS

To measure the impedance parameters in the wide dynamic range we need always the great number of the standards. The precise standards, used for the accurate measurements are very expensive, have great sizes and weight. Therefore, the appropriate devices have great cost and dimensions. In this report we describe the approach, which permits to reduce twice the number of standards, used for the widening of the measurement range. This approach is based on the measurement ofthe reciprocal impedance parameters on the two adjoining subranges of measurement.

Artur Augusto Martins, Regis Renato Dias
DEVELOPMENT OF SOFTWARE FOR AUTOMATION OF CALIBRATION PROCESSES OF ELECTRICAL MEASURING DEVICES USING OPTICAL CHARACTER RECOGNITION

A computer software to perform optical character recognition (OCR) of seven-segment displays, to optimize the calibration process of instruments and meters that make use of this type of display is proposed in this paper. The software works with a conventional low cost webcam that captures images, which will be handled and processed by the OCR algorithm implemented in the software, obtaining a numerical value corresponding to the value indicated in the instrument display as ASCII format which is capable of being interpreted by other applications of numerical computation. This paper will give information on how to implement an full automatic calibration process solution using this application and will be shown a table with the performance results of the software to recognize different numbers in different operating conditions, noting their effectiveness to perform the reading and recording processes of calibration.

L. C. Ribeiro, R. C. S. Machado, L. F. Rust
COMMUNICATION DEMAND MODEL IN CENTRALIZED MEASUREMENT SYSTEMS

The present work is a study of communication demand in centralized measurement systems. The study is based on a probabilistic consumption model and an architecture where a single communication server, typically located in a data concentrator, must provide communication for several pairs meter/display. We conclude that, for typical consumers (200kWh/month) and a specific architecture (one communication interface serving 10 pairs meter/display) an event of several (more than five) simultaneous communication requests is very rare. We also describe a criteria that maximizes the number of retransmissions of each message within a maximum “time to live”; such policy is important when the communication channel is unidirectional and there is no communication confirmation.

Andrés E. Legarreta, Javier H. Figueroa
AN IEC 61000-4-30 CLASS A POWER QUALITY MONITOR WITH A FLICKER METER BASED ON HILBERT TRANSFORM

This paper provides a novel analysis to implement a demodulation technique based on discrete Hilbert transform. Running on a DSP floating point architecture mounted in the power quality instrument PQ1000 ECAMEC fulfills the requirements of IEC61000-4-30, Class A category, over all the electrical measured parameters. Several analysis of optimal filter design and performance of signal processing are presented.

Page 506 of 977 Results 5051 - 5060 of 9762