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Page 374 of 977 Results 3731 - 3740 of 9762

Jakub Kováč, Jan Kučera
A MODULAR COAXIAL MULTIPLEXER WITH HIGH ISOLATION BETWEEN CHANNELS

An universal coaxial multiplexer for switching one measurement device between several measurement points is described. The coaxial multiplexer consists of independent switch modules (channels), which are controlled via optical fibres. The off-state isolation of multiplexer was measured to be better than -185 dB at 1 kHz. Properties of the multiplexer enable to use it in automation of high precision 2-TP and 4-TP coaxial a.c. bridges or other precise measurement applications.

Mirosław Kozioł, Janusz Kaczmarek, Ryszard Rybski
HIGH-PERFORMANCE TWO-PHASE SINE WAVE GENERATOR FOR IMPEDANCE BRIDGES

The paper describes the experimental study of a two-phase sine wave generator intended for use in an impedance metrology. It is based on a 20-bit digital-to-analog converter (DAC) based on the R-2R architecture. Some tests for evaluation of the generator were carried out. The excellent parameters of the DAC made possible achieve a very good stability of the complex voltage ratio which is about ± 0.25 part in 106 for the amplitude ratio and less than ± 0.25 µrad for the phase difference.

Kamil Kontorski
INTERPOLATION IN THE DIGITAL UNBALANCED IMPEDANCE COMPARATOR

Some details about digital balanced and unbalanced impedance comparators are presented in this article. A method of measuring an impedance ratio using the digital unbalanced comparator is described. Considerations about measurement errors connected with an experimental comparator setup are included. The research results are in an agreement with the theoretical assumptions.

Radek Martinek, Jan Vanus, Michal Kelnar, Petr Bilik, Jan Zidek
APPLICATION OF RECURSIVE LEAST SQUARE ALGORITHM TO ADAPTIVE CHANNEL EQUALIZATION

This paper deals with modern wireless transmission systems. It focusses on real implementation of recursive least squares (RLS) channel equalizer into the system of software defined radio (SDR), in order to minimize the distance between the signal and SNR transmitting channel noise and then reduce the error rate of bit error rate (BER) transmission. The authors aimed to conduct a real measurement using universal software radio peripheral (USRP). Experimental results suggest that researched RLS equalizer embodies better BER values in comparison to commercially most common equalizers of the least mean square (LMS) algorithm group. Moreover, the conducted experiments show that the usage of the SDR conception is very suitable for testing new principles in channel equalization field.

Piotr Jankowski, Janusz Mindykowski
ANALYSIS RESULTS OF EXPERIMENTAL VERIFICATION OF THE UNIVERSAL SWITCH IN THE POWER SUPPLY OF THE ELECTRODYNAMIC ACTUATOR

This paper presents the analysis results of experimental research of bidirectional switches based on thyristor SCR and transistor IGBT in a coil circuit of the electrodynamic actuator. A broader scope of application of the IGBT due to an oscillating frequency of the coil current has been shown because at small-capacitance of capacitor bank switching difficulties have arisen in the application of the SCR.

Miha Hiti
ALTERNATIVE CALIBRATION PROCEDURE FOR STRAIN GAUGE AMPLIFIERS

The article presents a method for calibration of strain gauge amplifiers with improved uncertainty in low voltage ratio range. The method is based on linearity check of amplifier using resistance circuit and combinatorial calibration method in combination with traditional strain gauge bridge simulators.

D. M. Szwarcman, E. Costa Silva, C. R. Hall Barbosa, E. Costa Monteiro
MAGNETOMETER BASED ON THE IMPEDANCE PHASE OF GMI SENSORS USING THE DMTD METHOD

Giant Magnetoimpedance (GMI) sensors are a new family of magnetic sensing devices that show potential to detect ultra-weak magnetic fields. Recent studies demonstrated that phase-based GMI magnetometers can achieve very high sensitivities. This work aims at the development of an enhanced GMI magnetometer, based on a high resolution digital phase reading electronic circuit that makes use of the Dual Mixer Time Difference method, to read the impedance phase variations of GMI samples.

Carlos R. Hall Barbosa, Jari Hällström, Lilian S. Ferreira, Marcio T. Silva, Luiz C. Azevedo
ALTERNATIVE METHOD FOR PROCESSING TAIL CHOPPED LIGHTNING IMPULSE WAVEFORMS

The International Electrotechnical Commission issued in 2010 a revision of the standards IEC 60060, describing how to calculate amplitude and time parameters used to evaluate high voltage tail chopped lightning impulse waveforms. However, the need for a full reference lightning impulse, in addition to the tail chopped impulse, creates difficulties for the tests and processing of the waveforms. This paper proposes an alternative method that precludes the need for the reference impulse.

Tomasz Grysiński, Zbigniew Moroń
IMPEDANCE ANALYZER FOR LOCAL MEASUREMENTS OF ELECTRICAL CONDUCTIVITY IN BIOLOGICAL OBJECTS

The subject of the publication is a portable device for measurements of impedance magnitude in the range of 25 Ω ÷ 2.5 kΩ, with the phase angle of -90 ÷ 0°, within the frequency band of 100 Hz ÷ 100 kHz. Small measuring current, 10 ÷ 100 µA, allows for the use of miniature sensors for the measurement of sample with volume as small as several mm³. The device was designed specifically for local measurements of electrical conductivity in biological objects.

Andrey Gadyuchko, Vladimir Kireev, Sören Rosenbaum
POTENTIALS OF MAGNETIC MEASUREMENT TECHNOLOGY IN DEVELOPMENT AND PRODUCTION OF ELECTROMAGNETIC ACTUATORS

The presented innovative magnetic testing method utilises the fact, that each commercially available electromagnet can not only be used as an actuator, but also comprises internal sensor functions. This allows a huge application variety in the fields of non-destructive testing and condition monitoring of electromagnetic systems during production and within the application in the field.

Page 374 of 977 Results 3731 - 3740 of 9762