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Sioma Baltianski
Impedance Spectroscopy: True and Observable Asymptotic Models

The decomposition process of the entire impedance spectra into its separate parts is accomplished by data fitting using a parametric distribution function of time constants in a convoluted form. Each particular part of the impedance spectrum is represented as an asymptotic model in the next step. Our technique lies within the branch of direct approaches showed in a concept map that describes analysis options of Impedance Spectroscopy. The direct fitting of the impedance spectrum by a detailed equivalent circuit is challenging due to its ambiguity. A comparative analysis of the asymptotic models is performed using different fitting functions. It is shown here that only Gauss impedance can obtain a "True" asymptotic model. All other known distribution functions used for impedance fitting result in only "Observable" asymptotic model. Correct interpretation relies on obtaining accurate data over wide ranges of frequencies, impedances and temperatures. The results were obtained using a custom-made impedance measurement system based on Precision Impedance Analyser and a Lock in Amplifier. The samples were dense ceramics tested in the temperature range of 200-475 ºC and the frequency range of 10^-2-3×107 Hz.

Stanislaw Czapp, Kornel Borowski
Experimental verification of a new method of loop resistance testing in low voltage systems with residual current devices

A periodical verification of the effectiveness of protection against electric shock shall be performed in low voltage systems. The scope of this verification includes loop impedance/resistance testing. If a residual current device is installed in a tested circuit, this testing is problematic. A residual current device trips out during the test, because of the high value of measurement current. This precludes the execution of the test. In the paper a new method of loop resistance testing in low voltage systems is presented. Experimental verification of this method has proved that it enables performing the verification of the effectiveness of protection against electric shock without nuisance tripping of residual current devices. The advantage of this method is the high value of the measurement current – many times higher than the rated residual operating current of commonly used residual current devices. It is very important in terms of measurement accuracy.

Romuald Masnicki, Janusz Mindykowski
Examination of the Instrument for Power Quality Estimation - Case Study

Evaluation of measurement properties of digital instrument can be performed in several ways. The calibration procedures relay mainly on the use of one of two standard methods: using the pattern input data set or applying the pattern reference instrument. In paper, the case of measurement experiment with use of ten instruments for electrical power quality assessment is cited. All instruments met the terms of respective standards, and measured this same network voltage. But their indications differed significantly. The question is: what are the reasons of these differences in indications? Case study - based considerations concerning calibration procedures are presented, taking into account the configuration of the measurement channel as well as the way of the measurement information handling in separate parts of measuring channel. The performed methods of the channel calibration or its characteristics verification were presented, along with obtained exemplary results. The conclusions related to the reasons of instruments indications dispersion are formulated. Another approach to measurement characteristics verification, especially performed in software part of instrument, is proposed.

Eduard Lunca, Alexandru Salceanu, Silviu Ursache, Mirela-Adelaida Anghel
Evaluation of EMF Exposure from Digital Terrestrial Television Transmitters

This study presents results of a preliminary survey of the RF electromagnetic fields (EMFs) originating from digital terrestrial television transmitters. In situ-measurements of DVB-T2 signals were conducted in the city of Iasi, Romania, and its rural vicinity, where a 180 meters tall guyed mast for FM-/TV-broadcasting is installed. The measured Efield levels were found to be well below the exposure limits recommended by the International Commission on Non-Ionizing Radiation Protection (ICNIRP) for the general public.

David Moure, Pedro Torres, Daniel M. Toma, Joaquin del Rio, Antoni Manuel
Data Acquisition System for Volcano Monitoring With Real-Time Transmission, Low Cost and Low Power Consumption

An acquisition system has been developed as an evolution of the gDT316 and gCNT16 dataloggers [1]. This new datalogger, gDT524, has several advantages in comparison with the previous versions. The main features, beside the low power consumption and low cost, are: an A/D converter with 24 bits fivechannels inputs, two 16 bits counters, meteorological sensors, real time clock with synchronization over NTP, micro-SD storage and GPRS communications through any standard modem with AT commands. Here we describe this device, developed in order to acquire low rate parameters related with volcano activity.

Hu Lizhi, Ma Zhichao, Xu Jie, Zhang Yu, Xu Liang, Dong Lian, Lai Lei, Sang Yu
Calibrations of Satellite Navigation Signal Simulator channel-delay based on Hilbert Transform Envelope Detection Method

Satellite navigation signal simulators are widely used in validation of navigation system and test of navigation receivers, so the correctness and accuracy of the signal simulated are highly concerned in the field of satellite navigation. Channel-delay is one of the important parameters in Calibration for Satellite Navigation Signal Simulators. This paper designs an auto-test system of channel-delay based on Hilbert Transform Envelope Detection method, which can automatically complete multiple test of channel delay and calculate the uncertainty of measurement through high speed oscilloscope. In order to determine the exact location of the turning point, the system processes the signal by using the envelope detection method based on Hilbert Transform, and the minimum point of the signal level envelope is used as the turning point. Then, the channel delay of the simulator is finally obtained. The actual results show that the method can improve work efficiency, and is capable to raise the channel delay measurement accuracy up to 0.1ns. In conclusion, analysis of the test result implies that this method can be applied to test and calibration of the channel delay of the simulator. This methods also can be applied to high-precision calibration of GNSS simulator zero value and pseudorange.

Maria Magdalena Poenaru, Fănel Iacobescu, Albert-Ciprian Anghel, Alexandru Sălceanu, Mirela-Adelaida Anghel
Active power quality assessment through interlaboratories comparison

Nowadays, an independent assessment of the technical performance of laboratories is necessary, in order to assure the validity of measurement results. The article presents the assessment of laboratories which participated at an inter-laboratories comparison (ILC) within active power field. This interlaboratories comparison had been performed on a period of 8 months and a number of 17 laboratories participated. The main goal of this intercomparison was the assessment of laboratories capabilities that perform verifications of active electrical energy meters and a travelling measurement standard was used.

Yolanda. A. Sanmamed, Javier Diaz de Aguilar, Miguel Neira
AC Resistance Measurement System at CEM

This paper describes the ac resistance measurement system developed at CEM. It consists on a four terminal-pair coaxial bridge that allows the measurement of ac resistance with traceability to dc resistance by means of a calculable resistor with a nominal value of 10 kΩ. This coaxial bridge enables the determination of ac resistance standards between 1 Ω and 100 kΩ, in a range of frequencies from 40 Hz to 5 kHz, with an expanded uncertainty between 1 µΩ/Ω and 5 µΩ/Ω, depending on the nominal value of the resistor and the measurement frequency.

Cristian Fosalau, Ionel Hogas, Cristian Zet, Daniel Petrisor
A PSpice Model for Sensors Based on Stressimpedance Effect

In the paper, a new PSpice model aimed for simulating the stressimpedance effect in magnetic amorphous microwires is presented. The application of the model is made on a highly sensitive strain gage whose characteristic depends both on the applied strain and on the frequency of the current flowing through it. The characteristic to be modelled is a nonlinear surface representing a complex impedance, which has been implemented in PSpice using ABM functions, starting from the experimental characteristics of the sensor. The benefit of our modelling method is that it may be customized to a certain device exhibiting particular features, thus leading to a higher accuracy for a large range of operation. In our example, the surface was approximated by 2-variables polynomials, but, generalizing, any other type of functions may be employed for curve fitting. Another advantage of the method is that it can be extended to other devices nonlinearly working on spaces of more than 2 dimensions.

Zsolt Kemény, Zsolt János Viharos, Krisztián Balázs Kis, Róbert Csontos, Tamás Kovács, Kornél Németh
Measurement and estimation of surface resistance on ESD-protected workstations

The prevention of electrostatic discharge (ESD) is an absolute must in the electronics industry, and surfaces of workstations have to be of specific resistance for effective ESD protection. The R&D project presented in the paper investigates the—so far rarely researched—dependence of worksurface resistance on ambient conditions and surface contamination. Upon examination of known and assumed dependencies, measurement and instrumentation are outlined, relying on existing automated facility management, autonomous devices, and manual measurement/logging. Further parts of the paper report on an ongoing analysis of the data being obtained, as well as their use in building models of surface resistance that can be applied in optimizing work and maintenance processes in the electronics industry.

Page 320 of 977 Results 3191 - 3200 of 9762