MEASUREMENT OF RMS VALUES OF NON-COHERENTLY SAMPLED SIGNALS

Martin Novotny, Milos Sedlacek

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.

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IMEKO-TC4-2004-049.pdf

DOI

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IMEKO TC

TC4 - Measurement of Electrical Quantities

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