Publications (4)0 Total impact
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Article: Measurement of RMS values of non-coherently sampled signals
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ABSTRACT: If the RMS value is gained by digital processing of sequence of signal samples, both uncertainty and bias of the measured value depend on the algorithm used. Since in practice signal sampling is usually non-coherent, leakage occurs in signal DFT spectrum and definition of the RMS of periodic signals in time domain is violated. The paper compares three different DSP algorithms of RMS measurement by non-coherent sampling from the point of view of measurement bias and uncertainty for various leakage levels and data window used. Results of simulations and example of measurement are evaluated for monofrequency signals. For non-coherent signal sampling a new and effective approach to RMS value measurement in time domain, a new method of finding exact signal frequency (different from those of DFT grid) based on two DFT phase spectra computation, and a method of automatic RMS value bias correction in frequency domain are presented. The reported results can easily be extended to multifrequency signals. -
Article: To the uncertainty of DFT-based DSP algorithms used for processing multifrequency signals
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ABSTRACT: The paper analyses effect of windowing a multi-frequency signal on the result of calculating signal parameters based on DFT. Influence of window side-lobes of nearby harmonic signals on the result of computation depends on the on the used window and on the difference in the two components magnitudes and frequencies. There are several other sources of resulting bias and uncertainty of measurements based on such algorithms. These influences are also briefly mentioned. The presented examples concern two methods of estimating RMS value, but the described principle is applicable to all algorithms based on DFT. Both theoretical relations and simulation results are included. -
Article: The influence of window sidelobes on DFT-based multifrequency signal measurement
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ABSTRACT: One of the causes influencing the uncertainty of the measured parameter is the mutual influence of the window spectra contained in the multifrequency signal spectrum. This paper analyses the effect of window spectrum sidelobes on the evaluation of multifrequency signal RMS value estimated by two DFT-based techniques (the “mainlobe method” and RMS value estimation using interpolated DFT). The RMS bias caused by window sidelobes when applying twelve different generalized cosine windows is compared. Both simulation results and theoretical relations are included. The presented principle is applicable for all DFT based algorithms, not only for those used for RMS value estimation.Computer Standards & Interfaces. -
Article: Measurement of active power by time domain digital signal processing
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ABSTRACT: This paper compares DSP time domain algorithms of one-phase active power measurement by non-coherent sampling that are superior to some frequency domain algorithms in active power estimation of non-sinusoidal signals. The measurement bias, uncertainty and sampling time necessary for the required accuracy are compared for various data windows with the use of simulations and measurements. Both monofrequency and multifrequency signals are dealt with. Analytical formulas are presented for the active power bias for rectangular and general cosine windows and for standard uncertainty of active power measurement. A simple method is described for correction of the multiplexing delay in power measurement using multiplexing DAQ boards. The information from this paper can also be used for measuring energy consumption and three-phase power.Measurement.
