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Yury K. Rybin
SYNTHESIS OF TEST MEASURING SIGNALS

Different models of measuring signals are considered. Their merits and demerits are discussed. A generalised model is offered on the basis of pulse string with the given shape, amplitude and duration. This model is equally suitable for describing deterministic, random and pseudorandom signals, both analogue and digital. The results of the synthesis of periodic signals with prescribed spectrum and random signal with given distribution law are presented.

J. M. D. Pereira, O. Postolache, P. Girao
IMPROVING PERFORMANCE OF ENCODERS BASED SYSTEMS USING WAVELET TECHNIQUES

This paper aims at the accuracy improvement of low-cost encoders based systems. Calibration data together with the approximations and details of wavelet decomposition are used to obtain some important parameters of absolute encoders. Differential and integral non-linear errors are estimated and their values are used to increase measurement accuracy. An error compensated system can easily be obtained by including the encoder, a microcontroller and a memory with a code conversion table. Simulation and experimental results, obtained from a low-cost angular encoder, are used to validate the proposed characterisation method based on wavelet data processing.

Domenico Alessandro Lampasi, Luca Podestà
COMPARISON OF DIFFERENT PARAMETERS FOR THE ANALYSIS OF ELECTRICAL POWER SYSTEMS UNDER NONSINUSOIDAL CONDITIONS

In modern power systems the hypothesis of pure sinusoidal waveforms is less and less realistic. The removal of this hypothesis has both theoretical and practical consequences. Some classical electrical quantities lose their physical meaning and do not provide useful information. On the other hand, new parameters may be introduced in order to characterize a system under nonsinusoidal conditions. A relevant feature of such parameters should consist in the measurement of the non-fundamental power and in the evaluation of the distortion introduced by loads. This paper presents analytical and experimental considerations about classical and new parameters suitable for the analysis of nonsinusoidal systems. Some tools like Fault Function, Amplitude Harmonic Distortion, Distortion Power and Instantaneous Power Harmonics are proposed in this paper for the first time. The considered parameters may be divided in two general classes: single-harmonic based parameters and global parameters.

Janusz Sawicki
ELIMINATING IMPULSIVE DISTURBANCES USING ADAPTED WEIGHTED MEDIANS

The idea of adaptive weighted median filtering of disturbed signals is presented in the contribution. The disturbance is assumed to be impulsive, hence linear filters are not a suitable tool for elimination of such pulses. After a short review of literature concerning weighted medians and their properties a piecewise linear process is analyzed and optimum weight vectors of the median filter are determined.

R. M. Mirsalimov, L. R. Bekirova, A. A. Abbas-zadeh
PROCESSING OF THE RADIATION MEASUREMENT SIGNALS IN THE SPECTROMETRIC DEVICES OF REMOTE SOUNDING

Undersatellite systems of remote sounding (USRS) of the terrestrial plants are enough effective for the solution of many important problems. Research of the natural resources, monitoring of the environment's state, observation of state of the agriculture and water facilities, also the natural cataclysms development dynamics observation problems, etc. are among them. The remote sounding for the military and prospecting purposes is very important as well. In turn, USRS, equipped by board special gears and computer facilities, are realized on the basis of aircraft, including the small-sized and cost-effective pilotless aircraft (planes, helicopters). The conditions of measurement, conversion and processing of the signals in USRS demand higher and rigid technical and metrology indexes of the board devices. Multi-channel spectrometers of the various types are one of the board devices, carried out the measurement in visible range and near infrared range of electromagnetic radiation's spectrum. The output signals of these spectrometric devices are formed after preprocessing the radiation signals, coming from the researched terrestrial plant, the measurement standard and the sky accordingly, on the board. Therefore the measurements with help of the spectrometric devices are fulfilled in the following four different regimes: "terrestrial plant", "sky", "standard" and "darkness current", which are usually installed with help of the special optical-electromechanical blocks (modulators), characterized by lag effect, hardness of construction and setup, high consumption of electric energy and insufficient reliability. All showed above raise mass-size indexes of the spectrometric devices, hardware expenditures, diminish speed and reliability.

Olga Kosheleva, Sergio Cabrera, Brian Usevitch, Edward Vidal Jr.
HOW TO BEST COMPRESS 3D MEASUREMENT DATA UNDER GIVEN GUARANTEED ACCURACY

The existing image and data compression techniques try to minimize the mean square deviation between the original data f(x, y, z) and the compressed-decompressed data fcd(x, y, z). In many practical situations, reconstruction that only guaranteed mean square error over the data set is unacceptable: for example, if we use the meteorological data to plan a best trajectory for a plane, what we really want to know are the meteorological parameters such as wind, temperature, and pressure along the trajectory. If along this line, the values are not reconstructed accurately enough, the plane may crash – and the fact that on average, we get a good reconstruction, does not help. What we need is a compression that guarantees that for each (x, y) the difference | f(x, y, z) - fcd(x, y, z) | is bounded by a given value Δ – i.e., that the actual value f(x, y, z) belongs to the interval [fcd(x, y, z) - Δ, fcd(x, y, z) + Δ]. In this paper, we describe new efficient techniques for data compression under such interval uncertainty.

G. F. Malykhina, A. V. Merkusheva
METROLOGICAL ASPECTS OF NON-STATIONARY SIGNAL TRANSFORMATION FOR DYNAMIC SPECTRUM ANALYSIS

The non-stationary signal spectrum in the information measurement system (IMS) is based on twodimension time-frequency transformation (TFT). Although the precision of the computer TFT provides the errors much less than a limit of practical significance, the transformation result relates not to uniquely determined point, but to some uncertainty cell, the size of which is determined by “metrological” characteristics (MC) of TFT. The cell may change its form in the time-frequency domain, but its limitations stays not smaller than limit minimum value that relates to resolution limit capability of TFT. In the paper, we give the MC estimation for one of widely used spectrogram TFT. The global (applicable to the whole time-frequency plane) and local MC (legible only near some definite point), and their correlation are given in the paper.

V. M. Sapelnikov, A. D. Maksutov, G. Ju. Kolovertnov, R. A. Khakimov
FUNCTIONAL DIGITAL-TO-ANALOG CONVERTERS – NEW OPPORTUNITIES OF INSTRUMENT MAKING

The digital-to-analog converters (DAC) are widely applied for transformation of signals in an informational - measurement technology, radio engineering and instrument making. They are a potent resort of increase readout accuracy. However existing a DAC can execute only linear transformation of a kind Uout = k Uref. At the same time in different areas of engineering it is necessary with a split-hair accuracy to replicate non-linear functional connections. For example, such necessity arises at construction digital-controlled of phase changes and calibrators of a phase, as the relation of a phase shift to change of a controlled variable is always non-linear. The most preferential way for implementation of this operation - usage a DAC.

Amauri Oliveira, Lígia S. Palma, Alexandre S. Costa, Raimundo C. S. Freire, Antônio C. C. Lima
A CONSTANT TEMPERATURE OPERATION THERMORESISTIVE SIGMA-DELTA SOLAR RADIOMETER

In this paper we propose a feedback system, with thermo-resistive sensor, based on sigma-delta modulation. The system uses a one-bit sigma-delta modulator in which considerable part of conversion functions is performed by a thermoresistive sensor. The sensor is modelled using the power balance principle and the applied measurement method is constant temperature. This transducer architecture is able to realize digital measurement of physical quantities that interacts with the sensor: temperature, thermal radiation and fluid velocity. This paper presents simulations results of this system applied to thermal radiation measurement.

Franco Castelli
THE ZERO-FLUX CURRENT TRANSFORMER TO IMPROVING ACCURACY WITH APPLICATIONS FOR DISTORTED WAVEFORMS AND DC BIAS

Current measurements on electrical power systems very often concern nonsinusoidal conditions, due to the presence of distorting loads connected to the network (typically because of the presence of power electronic components) and the consequent harmonic pollution. In addition the presence of DC components, superimposed to alternating ones can make it impossible to correctly use the current transformers (CT’s) and gives rise to the burden and composed (namely due to the distorted waveforms) errors, that are arising from the presence of the core flux in CT. Moreover saturation, hysteresis, and polarization are supported by the core flux. The presence of the core flux is the difference between a real CT and an ideal one.

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