A numerical model of a general purpose commercial equipment for current versus voltage (I-V) and differential capacitance versus voltage (C-V) measurement of active devices is presented. The good agreement between the model results and experimental data show that the model takes into account the main error sources of the instrument and can be used as a base to perform error correction and to implement a calibration procedure.

The inrush currents generated during a energization of power transformer can reach very high values and may cause many problems in power system. In this paper method for controlled energization of power transformer based on measuring of remanent flux of magnetic core is presented. The remanent flux is measured and memorized at the last de-energization of transformer and then applied at next energization. Experimental results of inrush currents at controlled energization of transformer are presented.

The incoming technologies allowing for a massive use of remote driven instruments could improve the quality of the experiments in laboratory sessions, especially for what concerns the very specific high level classes. Moreover, taking into account the large number of students, the availability of the lab can be greatly extended. In order to give flexibility and high performances to the educational tool a user friendly virtual instrument has been realised allowing distance learning. Some basic experiments can be performed by the user, namely the analysis of both the RC and the RLC circuits, frequency measurements and also measurements on audio-frequency amplifiers. Indeed, the user can make the choice of the experiment which he is interested in and can choose the particular procedure among the implemented ones. By using the adopted procedure the user can carry out a proper training without loosing the contact with real instruments. In order to emphasize the features of the implemented system some examples are presented. A 'presence effect' will be added in the next future, by using a web camera in the lab.

Instrument transformer accuracy testing by the method based on integration of DFT and virtual instrument concept, composed of standard hardware (osciloscope, PC) and specific software is outlined. The structure of the realized virtual instrument for accuracy test of current transformer by DFT method is shown. The method has experimentally verified and compared with measurements made with the classical complex Hohle compensator.

The goal of this paper is to provide analysis of Universal Serial Bus, multipurpose communication interface, in application to laboratory measurement systems. This interface is compared with others, established measurement interface standards, especially IEEE-488, in a view of requirements in this specific application. The current market offer and trends in software and hardware design are reviewed. Obstacles to common use of USB in measurements are pointed out and projections to the future use are made.