Performances of ΔΣ modulators are evaluated by applying a coherently sampled tone and by estimating powers of the in-band tones and noise. In particular, the power of the shaped noise is usually estimated by subtracting the evaluated input tone from the output data and by integrating the power spectral density estimated by means of the periodogram. Although the coherency, the finite number of processed samples induces spectral leaking of the wide. band noise, thus affecting the noise power estimate. To cope with such an issue, usually data are weighted by the Hanning sequence. In this paper, the noise power estimation error induced by the use of such window is investigated, and a criterion for choosing the minimum number of samples N which bounds the relative leakage error within a specified maximum value is explicitly given. Moreover, it is shown that, for an N, such an error is negligible for modulator orders lower than 3. Higher order modulators require the use of a large number of samples to bound the relative error of the noise power estimate when high oversampling ratios are employed.

A method for the assessment of the dynamic behaviour of heavy current shunts is described, which is based on the evaluation of the shunt frequency response through spectral analysis of input and output measured signals. The method has been tested by applying it to simulated current impulses and experimented in the case of a pulse current, generated by the discharge of a cable capacitance, measured by a thin walled coaxial-tube shunt.

Time Domain Spectral Analysis is presented in this paper as a new, original approach to the analysis of signal spectrum (having samples of the measured signal). The uniqueness of this method is in avoiding of any kind of Fourier transform, which showed to be of limited accuracy when the samples' errors (measurement imperfections) are taken into account, even applying windows and various approximations. The majority of calculations are based on our previously developed method for high accuracy measurement of a single sine wave. The basic idea of this method is to extract all time domain samples of a particular wave from samples of the whole signal, and then to calculate parameters of that component by applying the method for measurement of a single sine wave. This approach has been tested with extended and rigorous computer simulations (explained further in the text) and partially in real laboratory measurements. It is demonstrated that estimated accuracy of parameters of the fundamental wave is about 4 ppm, even though the samples' errors are of the order of 20 ppm. The estimated accuracy of the higher harmonics is better than 500 ppm (regardless of their number, and the same for amplitude and phase).

In the last years the increased interest about power quality, forced international working groups to define new standards for testing and measurement techniques. In this paper a pc-based power quality instrument is proposed, according to IEC 61000-4-7 and standard IEC 61000-4-30. It is a low-cost and easily reconfigurable instrument able to measure harmonics, interharmonics and amplitude disturbances and supply unbalance. The complete instrumentation has been tested using standard test procedures in order to verify its accuracy limits.

The present paper deals with the selected problems of electrical energy quality assessment in the power system under non-sinusoidal conditions, i.e. the real power system. The principals are understood by the author as the three-segment block which consists of the basic definitions concerning power quality and its assessment, methods to determine electrical power quality indices by using the appropriate mathematical tools, as well as the related instrumentation for solving a problem of electrical power quality assessment. In the paper, these three fundamental parts for solving the electrical power quality assessment problem have been described and commented on. All analyses have been illustrated by the real data from ship electrical power systems.