9762 papers found
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.
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...
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...
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.
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...
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 f cd ( 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...
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...
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 U out = k U ref . 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...
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...
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...