This paper analyzes accuracy of algorithms commonly adopted in instrument devoted to the detection and the characterization of voltage dips (also called sags). This analysis is particularly interesting because the results of dip measurements are utilized for calculation of severity levels and the site index assessment that are parameters adopted in determination of quality level of power supply, but also in developing planning and design criteria of new electrical power grid or for selecting equipment with proper intrinsic immunity. Anyway there is a certain degree of freedom left to instrument manufacturers (f.i. the choice of dip detection algorithm) and it can be found that different instruments significantly disagree in some actual measurements. The paper starts with an insight about dip phenomenon analyzing how accuracy impacts on severity index calculation. The results are applied, for accounting the systematic deviations in testing accuracy of commercial instrument, is presented. Then, experimental results derived form the accuracy testing in dip measurements of a commercial power quality instrument are shown.

In this paper an analysis of conducted harmonic emissions of different types of lamps is presented. The growing use of non-linear loads (pc, printers, electronic devices, etc.) connected to power supply systems and their variability with time, are responsible of a continuously changing harmonic content in the distribution system. Therefore, to analyze their real behaviour, the lamps were tested using the general power supply of an office building as the source voltage, so that the harmonic distortion of the test voltage changed depending on the time of day and on different weekdays. Accordingly, the resulting current waveforms of the lamps significantly changed. The mean values of harmonic distortion of currents were analyzed and the differences between the lamps are shown.

Two acquisition techniques pointed out for the static and dynamic test of high resolution DAC by low resolution ADC are analyzed and compared. These two techniques differ on the basis of the specific approximated evaluation of the DAC output voltage.
The interest to the comparative analysis is justified by the aim to separate the influence of the acquisition technique from that of the processing algorithm on the evaluation of the accuracy of the test.
The comparing analysis is performed on the basis of the accuracy to reconstruct the output signal of the DAC. The error occurring in the evaluation of the DNL is taken into consideration for the static test. The error occurring in the evaluation of the Spurious Free Dynamic Range is taken into consideration for the dynamic test.
Results of the numerical tests to compare the accuracy of the two acquisition techniques are shown and discussed.

Cloud height, wind speed and direction at cloud height play an important role in air safety. This paper presents a low-cost system based on digital consumer cameras to estimate cloud base height. It is shown that both wind speed and direction at cloud level can also be obtained with this system. The method is based on triangulation and uses image registration to identify common cloud features in photographs taken from different positions. The wind speed and direction is obtained from two time-lapsed pictures taken from the same position.

The paper describes some problems connected to the reference data set generation for the validation of metrological software. The validation concerns the Gaussian procedures for solving the task of the approximation of geometric features.