PL
 |
EN
Preferencje help
Polish version English version Język
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 5

Liczba wyników na stronie
first rewind previous Strona / 1 next fast forward last
Wyniki wyszukiwania
help Sortuj według:

help Ogranicz wyniki do:
first rewind previous Strona / 1 next fast forward last
1
Content available Application of poly-harmonic signals to eddy-current metal detectors and to advanced classification of metals
Svatoš J., Pospíšil T., Vedral J.
Metrology and Measurement Systems
|
2018
|
Vol. 25, nr 2
387--402
EN
A limited ability to discriminate between different materials is the fundamental problem with all conventional eddy-current-based metal detectors. This paper presents the use, evaluation and classification of nontraditional excitation signals for eddy-current metal detectors to improve their detection and discrimination ability. The presented multi-frequency excitation signals are as follows: a step sweep sine wave, a linear frequency sweep and sin(x)/x signals. All signals are evaluated in the frequency domain. Amplitude and phase spectra and polar graphs of the detector output signal are used for classification and discrimination of the tested objects. Four different classifiers are presented. The classification results obtained with the use of poly-harmonic signals are compared with those obtained with a classical single-tone method. Multi-frequency signals provide more detailed information, due to the response function - the frequency characteristic of a detected object, than standard single-tone methods. Based on the measurements and analysis, a metal object can be better distinguished than when using a single-tone method.
2
Content available DAC testing using impulse signals
Vedral J., Fexa P.
Metrology and Measurement Systems
|
2012
|
Vol. 19, nr 1
105-114
EN
The Multi-Tone (MT) signal with uniform amplitudes can be used for DAC testing. This paper shows an easier way to generate a MT signal using several impulse signals. The article also analyzes qualities of methods for testing the dynamic parameters of Digital to Analog Converters using an impulse signal. The MT, Damped Sine Wave (DSW) and Sinx/x (SINC) signals will be used as the source for these tests. The Effective Number of Bits (ENOB) and Signal to noise and distortion (SINAD) are evaluated in the frequency domain and they are modified using the Crest Factor (CF) correction and compared with the standard results of the Sine Wave FFT test. The first advantage of the test using an impulse signal is that you need fewer input parameters to create the band signal for testing the DAC. The second one is to reduce the testing time using a band signal in comparison with multiple tests using a single sine wave.
3
Content available Metal detector excited by frequency-swept signal
Svatoš J., Vedral J., Fexa P.
Metrology and Measurement Systems
|
2011
|
Vol. 18, nr 1
57-67
EN
This paper describes the theoretical background of electromagnetic induction from metal objects modelling. The response function of a specific case of object shape - a homogenous sphere from ferromagnetic and nonferromagnetic material is introduced. Experimental data measured by a metal detector excited with a linearly frequency-swept signal are presented. As a testing target various spheres from different materials and sizes were used. These results should lead to better identification of the buried object.
4
Content available remote Signal processing in partial discharge measurement
Vedral J., Kříž M.
Metrology and Measurement Systems
|
2010
|
Vol. 17, nr 1
55-63
EN
The paper presents traditional analogue and digital techniques in partial discharge measurement. The discharge current pulses are measured from high voltage machines like power plant generators and transformers. The presented modern digital techniques are suitable for all measurements where impulse energy will be calculated.
5
Content available remote Methods for economical test of dynamic parameters ADCs
Vedral J., Fexa P., Svatoš J.
Metrology and Measurement Systems
|
2009
|
Vol. 16, nr 1
161-170
EN
This paper describes two methods for economical test of dynamic parameters ADCs. First method is Exponential Fit Test, second method is Wobbler Test. Common testing methods are mentioned as far the accuracy and time necessary for the complete test are concerned. The tests for fast evaluation of the dependence of an effective number of bits on frequency of input signal are described and the comparison of proposed method with the standard methods is given. The suitable area of proposed method application is "each-piece" factory testing requiring extremely short time testing.
first rewind previous Strona / 1 next fast forward last
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.