RMS value measurement based on classical and modified digital signal processing algorithms

Abstract

If the RMS value is obtained by digital processing of a sequence of signal samples, both the uncertainty and the bias of the measured value depend on the algorithm used. Since in practice signal sampling is usually non-coherent, leakage occurs in the signal DFT spectrum and the definition of the RMS of periodic signals in the time domain is violated. This paper presents an overview of estimation of RMS values by comparing five different DSP algorithms of RMS measurements by non-coherent sampling from the point of view of measurement bias and uncertainty for various leakage levels and the data window used. The results of simulations and examples of measurements are evaluated for both monofrequency and multifrequency signals. For non-coherent signal sampling, we compare time domain signal processing based on signal windowing with classical RMS estimation. This is shown to be an effective approach to RMS value measurement. A new method for finding the exact signal frequency by non-coherent sampling is introduced, and a method for effective RMS value bias correction in the frequency domain is presented. Methods for estimating RMS values in the time and frequency domains are compared.