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Vedran Srsen, Sandor Dembitz, Petar Knezevic
ANALYSIS OF ECHO IN PSTN-TO-VOIP TRANSMIGRATION

The growth of the Internet and its impact on other communication technologies is nothing new today. One of the issues is the migration of voice traffic from Public Switched Telephone Network (PSTN) to packet networks. In this paper we will show the impact of that migration on the occurrence of echo, and the use of solutions that are implemented in the VoIP network.

Bruno Andò, Nicola Pitrone
DISTANCE LEARNING IN LABORATORY SESSIONS

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.

Umberto Pogliano
FAST AND PRECISE ALGORITHM FOR TRACKING SINUSOIDAL SIGNALS

The paper describes an algorithm for fast and precise tracking of sinusoidal signals. The implementation is designed for a system where the acquisition and processing of the input signal samples are performed in real time. Few instructions are required at every step, so the algorithm can be applied to signals having a relative high frequency.

Slobodan Škundric, Dragan Kovacevic, Slobodan Mikicic
INSTRUMENT TRANSFORMER ACCURACY TESTING BY DFT METHOD

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.

Milan Stork
COUNTER BASED FREQUENCY SYNTHESIZER

This paper describes architecture a new pure digital frequency synthesizer based on generators, counters and a register. The technique described here is much simpler then other method. Presented synthesizer is the most suitable for the design of VLSI architectures or for programmable Large Scale Integration. On the other hand, this synthesizer has a disadvantage in low output frequency, but this can be overcome by using this synthesizer together with phase locked lop.

Tomasz Twardowski
WILL USB BE A STANDARD OF PC - INSTRUMENTATION COMMUNICATION?

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.

Ivan Gašparac, Zlatko Maljkovic, Mario Vražic
VIBRATIONS MEASUREMENT DURING HYDROGENERATOR TESTING

This paper presents the results of vibration measurement during several specific tests of 35 MVA hydro-generator.

Jiri Brossmann, Jaroslav Roztocil, Vojtech Ruml, Dusan Varga
SOFTWARE DEVELOPMENT FOR ADC TESTS

Object based universal software system for ADC testing which enables an easy programmer’s access and expansion (update) is introduced in this paper. The basic idea of the object oriented design and some aspects of the software solution of the ADC testing are described.

Josep M. Torrents, Ramon Pallàs-Areny
SENSING OIL CONDITION THROUGH TEMPERATURE COEFFICIENT OF DIELECTRIC CONSTANT

Time-scheduled oil changes in internalcombustion engines are often performed well before the oil starts to significantly lose its lubricating properties. A check of oil properties using laboratory analysis methods is expensive. Using the same techniques during service would be extremely difficult. Consequently, oil is seldom analyzed before substitution, which results in oil wasting. This paper shows that in the low frequency range, the temperature coefficient of the dielectric constant of lubricating oils depends on whether the oil is fresh or it has been used. Hence, the change in dielectric constant from ambient temperature to working temperature is a possible sensing method for engine oil condition.

Darko Vasic, Vedran Bilas, Davorin Ambruš
PULSED REMOTE FIELD TECHNIQUE IN FERROMAGNETIC TUBE WALL THICKNESS AND INNER DIAMETER MEASUREMENT

In conventional applications of the remote field eddy current technique, a probe with low frequency sinusoidal excitation is used for measurement of ferromagnetic tube wall thickness. An additional probe with high frequency excitation is required for measurement of the tube inner diameter (electrical caliper). In this paper, this is illustrated with results of finite element analysis. However, the waveform of the pulse driving current and shorter probe length potentially allow the measurement of the inner diameter and the wall thickness with the same probe. We present results of our experiments on ferromagnetic tubes with internal and external defects that confirm applicability of the pulsed remote field technique for measurement of the both quantities.

Page 918 of 939 Results 9171 - 9180 of 9382