Abstract: A method of determining the fundamental component and the harmonics (I′(&ohgr;)) of a measured electric quantity (M) is described, where the measured quantity (M) is processed by an analog signal processing circuit (15), the processed measured quantity is sampled and subject to an analog-digital conversion with a subsequent discrete Fourier transform (DFT).

Abstract: The present invention relates to a process for determining harmonic oscillations of a fundamental component of an electrical signal, wherein the signal is sampled with a sampling frequency corresponding to a multiple of the fundamental component's frequency. The sampled values of the signal are subjected, after analog-to-digital conversion, to a discrete Fourier transformation to determine the harmonic oscillations. The sampling is performed with a non-integer multiple of the frequency of the fundamental component and the discrete Fourier transformation is performed while the frequency resolution is increased over several periods of the fundamental component to determine the harmonic oscillations.

Abstract: A digital process for determining the effective value of a periodic electric test signal is provided, where the test signal is sampled during a sampling interval that differs in duration from the period of the test signal, and after performing an analog-digital conversion of the samples, they are squared, added up and averaged. The square root of the resulting average is calculated. To be able to determine the effective value rapidly and with a high accuracy according to this invention with a sampling interval that corresponds to two periods of the electric test signal with an odd numbered M of samplings with N samples that fall in one period of the test signal, the values up to and including the Nth sample are squared and added up. To this is added a correction factor that corresponds to half of the square of a subtotal formed from one-quarter of the Nth sample and three-quarters of the (N+1)th sample, where N=(M−1)/2. Then the average is calculated over the number M/2.

Abstract: The present invention relates to a process for determining harmonic oscillations of a fundamental component of an electrical signal, wherein the signal is sampled with a sampling frequency corresponding to a multiple of the fundamental component's frequency. The sampled values of the signal are subjected, after analog-to-digital conversion, to a discrete Fourier transformation to determine the harmonic oscillations. The sampling is performed with a non-integer multiple of the frequency of the fundamental component and the discrete Fourier transformation is performed while the frequency resolution is increased over several periods of the fundamental component to determine the harmonic oscillations.