The method of determining reason - and harmonics of an electrical parameter

摘要

The invention concerns a method to determine fundamental and harmonic oscillations (I'( omega )) of a measured electrical quantity (M), whereby the measured quantity is conditioned by an analog signal conditioning circuit (15), the conditioned measured quantity is sampled and subjected to an analog to digital conversion and to a subsequent discrete Fourier tranform (DFT). To determine very accurately the fundamental and harmonic oscillations (I'( omega )) of the measured electrical quantity (M) even when a relatively low quality signal conditioning circuit (15) is used, a correction value k( omega )) which characterizes the amount and phase of the frequency response is drawn from the storage (18). The measured amount and phase values existing after the Fourier transform (I( omega )) of the fundamental and harmonic oscillations are corrected with the correction factor (k( omega )).