Among the phenomena significantly aggravating the quality of electric energy in the grid two are especially important: voltage fluctuations and deformations of voltage and current sinusoids.
The aim of the study described in the present paper was to improve the accuracy of signal converting in power measurements in non-linear receivers. The measurements of voltage and current were performed by means of a PC with measuring a card PCL-818L and with application software DasyLab 6.0 enabling the registration and converting of signals.

A new definition is proposed for the effective number of bits of an ADC. This definition removes the variation in the calculated effective bits when the amplitude and offset of the sinewave test signal is slightly varied. This variation is most pronounced when test signals with amplitudes of a small number of code bin widths are applied to very low noise ADC's. The effectiveness of the proposed definition is compared with that of other proposed definitions over a range of signal amplitudes and noise levels.

In this paper, we investigate problems of D/A converters with non-uniformly sampled input data, and/or time-varying clock sources. The input digital data (which are stored in the memory to be read out and sent to a D/A converter) were obtained by sampling an analog waveform at non-uniform sampling intervals. (Quantization of data can also be considered as a form of non-uniform sampling.) Recently, there is available a new clocking system with a very fine time resolution and is capable of adjusting the clock period in a sample-to-sample basis. It is, therefore, interesting to consider the following question. "Given that the timing offset of each data sample is known, would it be beneficial to use this offset to adjust the read-out timing of the D/A converter?" To answer this question, we consider the following five different models: f₁(t) = Σ_n x(n T) g(t - n T), f₂(t) = Σ_n x(t_n) g(t - n T), f₃(t) = Σ_n x(n T) g(t - t_n), f₄(t) = Σ_n x(t_n) g(t - t_n), and f₅(t) = Σ_n x(t_n) g_n(t - t_n) where x(.) is the input analog signal, g(.) is the basic output pulse waveform of the D/A converter, T is the nominal sampling period and t_n is the n-th sampling time instance (for uniform sampling t_n = n T). Closed form expressions for the Fourier transform of the output signals for each model are derived. We also discuss some potential practical applications.

In this paper we present a sigma-delta modulator for wide-band base transceiver station receivers. The modulator, based on a four-path architecture, achieves an equivalent sampling frequency of 320 MHz, although the building blocks operate at only 80 MHz. The circuit in simulation achieves 94 dB signal-to-noise ratio with a signal bandwidth of 5 MHz centered around an intermediate frequency of 80 MHz. Behavioral simulations of the complete sigma-delta modulator, including the most important non-idealities, as well as transistor-level simulations of the most critical building blocks are reported.

The state of the art of the research on modelling of analog-to-digital converter-based measuring devices is surveyed. Main topics of modelling are reviewed according to the fields of prevailing scientific interest in metrological research such as quantization models, error models, and correction-aimed models. In these fields, recent developments are analysed with the aim of focusing both the contemporary situation and the imminent trends.