Temat: impedance - Prolib Integro

Skocz do pozycji: 1.

Tytuł:: Comparing methods of image reconstruction in electrical impedance tomography
Autorzy:: Rymarczyk, T.
Filipowicz, S.F.
Sikora, J.
Tematy:: impedance tomography
electrical impedance tomography
EIT; Pokaż więcej
Wydawca:: Politechnika Poznańska. Wydawnictwo Politechniki Poznańskiej
Powiązania:: https://bibliotekanauki.pl/articles/97630.pdf Link otwiera się w nowym oknie
Opis:: The problem of the image reconstruction in Electrical Impedance Tomography (EIT) is a highly ill-posed inverse problem. There are mainly two categories of image reconstruction algorithms, the direct algorithm and the iterative algorithm which was used in this publication. This paper presents the applications of the level set function for identification the unknown shape of an interface motivated by Electrical Impedance Tomography (EIT) by using a several level set algorithms. The conductivity values in different regions are determined by the finite element method. The applications were based on the level set method, the variational level set algorithm and the Mumford-Shah algorithm to solve the inverse problem.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 2.

Tytuł:: Using a particular sampling method for impedance measurement
Autorzy:: Lentka, G.
Tematy:: impedance measurement
impedance analyzer
particular sampling; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Czytelnia Czasopism PAN
Powiązania:: https://bibliotekanauki.pl/articles/221836.pdf Link otwiera się w nowym oknie
Opis:: The paper presents an impedance measurement method using a particular sampling method which is an alternative to DFT calculation. The method uses a sine excitation signal and sampling response signals proportional to current flowing through and voltage across the measured impedance. The object impedance is calculated without using Fourier transform. The method was first evaluated in MATLAB by means of simulation. The method was then practically verified in a constructed simple impedance measurement instrument based on a PSoC (Programmable System on Chip). The obtained calculation simplification recommends the method for implementation in simple portable impedance analyzers destined for operation in the field or embedding in sensors.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 3.

Tytuł:: Dynamic Impedance Cardiography : the system and its applications
Autorzy:: Cybulski, Gerard
Współwytwórcy:: Instytut Medycyny Doświadczalnej i Klinicznej im. Mirosława Mossakowskiego PAN.
Wydawca:: Department of Applied Physiology. Medical Research Centre Polish Academy of Science
Powiązania:: Prace habilitacyjne
Opis:: IV, 80 s. : ill., 25 cm
Bibliogr. zawiera 165 pozycji
Praca ukazała się w : Polish Journal of Medical Physics and Engineering 2005; 11 (3): 127-209
Dostawca treści:: RCIN - Repozytorium Cyfrowe Instytutów Naukowych

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Skocz do pozycji: 4.

Tytuł:: Bioelectrical impedance analysis in medicine
Autorzy:: Dubiel, Anna
Tematy:: BIA
bioelectrical impedance analysis
bioimpedance
impedance analysis; Pokaż więcej
Wydawca:: Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Powiązania:: https://bibliotekanauki.pl/articles/1075628.pdf Link otwiera się w nowym oknie
Opis:: The analysis of electrical bioimpedance (BIA) is a non-invasive, low cost and a commonly used approach for body composition measurement and assessment of clinical condition. There are a variety of methods applied for interpretation of measured bioimpedance data and a wide range of utilizations of bioimpedance in body composition estimation and evalution of clinical status. Bioelectrical impedance analysis is based on knowledge about the electrical properties of human body. The clues are provided here by elementary knowledge of the tissue and cellular structure of the organism and the basis of physics. The amount of electrical resistance (resistance) of a uniform object is directly proportional to its length (L) and specific resistance (ρ), and inversely proportional to its cross-sectional area (A). The impedance (Z) is a function of the mentioned resistance and reactance (XC), which in turn is inversely proportional to the frequency of the current and the electrical capacity of the system. BIA method can provide a reliable, safe and effective way to study body composition, as well as other parameters resulting from the distribution of water in the body. It can be used in the examination of body composition in both cases: healthy and chronic patients, with particular emphasis on diseases related to metabolism.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 5.

Tytuł:: A family of new generation miniaturized impedance analyzers for technical object diagnostics
Autorzy:: Hoja, J.
Lentka, G.
Tematy:: technical object diagnostics
impedance spectroscopy
impedance analyzer; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Czytelnia Czasopism PAN
Powiązania:: https://bibliotekanauki.pl/articles/220894.pdf Link otwiera się w nowym oknie
Opis:: The paper presents the family of three analyzers allowing to measure impedance in the range of 10 Ω<|Zx|<10 GΩ in a wide frequency range from 10 mHz up to 100 kHz. The most important features of the analyzer family are: miniaturization, low power consumption, low production cost, telemetric controlling and the use of an impedance measurement method based on digital signal processing (DSP). The miniaturization and other above-mentioned features of the analyzers were obtained thanks to the use of the newest generation of large-scale integration chips: e.g. "system on a chip" microsystems (AD5933), 32-bit AVR32-family microcontrollers and specialized modules for wireless communication using the ZigBee standard. When comparing metrological parameters, the developed instrumentation can equal portable analyzers offered by top worldwide manufacturers (Gamry, Ivium) but outperforms them on smaller dimensions, weight, a few times lower price and the possibility to work in a distributed telemetric network. All analyzer versions are able to be put into medium-volume production.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 6.

Tytuł:: Numerical analysis and experimental verification of the electrical impedance tomography method for monitoring of the packed-bed drying process
Autorzy:: Porzuczek, J.
Tematy:: drying
ectrical impedance tomography
impedance spectroscopy
chokeberry
EIDORS; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Czytelnia Czasopism PAN
Powiązania:: https://bibliotekanauki.pl/articles/175586.pdf Link otwiera się w nowym oknie
Opis:: This paper presents a method for online determination the spatial distribution of the moisture content in material being dried. It might be essential for monitoring and optimal control of the drying processes. The proposed method utilizes electrical impedance tomography. As the exemplary material for experimental research the black chokeberry (Aronia melanocarpa) was used. The relationship between electrical impedance of chokeberry and its moisture content was determined for wide range of frequency (0.02200 kHz). Experimental studies of the spatial distribution of the moisture content was performed in the cylindrical vessel equipped with 8-electrode circumferentially arranged. Voltage signal from the electrodes was acquired simultaneously using high-speed data acquisition module. Due to high impedance of the chokeberries, exceeding 109 Ω for dried matter, extraordinary instrumentation for stimulus sourcing and current measurement was necessary to be applied. On the other hand, raw chokeberries are characterized by several orders of magnitude lower impedance (103104 Ω), especially for high frequency. Wide range of observed impedance was able to be measured owing to use of the voltage stimulation instead of the current stimulation. The image reconstruction problem was solved using iterative Gauss-Newton algorithm in the electrical impedance and diuse optical tomography software package. The obtained results has shown satisfactory ability to localize insuciently dried part of the material. It was proved, that strong dependence between moisture content in chokeberries and its impedance in whole frequency range provides more meaningful information than simple resistance or capacitance measurement. Prospect for the improvement of the spatial resolution of humidity imaging was also discussed.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 7.

Tytuł:: Woltomierz wektorowy z wykorzystaniem DFT na bazie układu FPGA dla analizatora spektroskopii impedancyjnej
A vector voltmeter using DFT based on the FPGA chip for the impedance spectroscopy analyzer
Autorzy:: Lentka, G.
Kościński, P. A.
Smużyński, K. D.
Tematy:: spektroskopia impedancyjna
pomiary impedancji
impedance spectroscopy
impedance measurement; Pokaż więcej
Wydawca:: Stowarzyszenie Inżynierów i Techników Mechaników Polskich
Powiązania:: https://bibliotekanauki.pl/articles/154373.pdf Link otwiera się w nowym oknie
Opis:: W pracy zaproponowano i przetestowano nową koncepcję woltomierza wektorowego z wykorzystaniem cyfrowego przetwarzania sygnałów. Obliczenia prowadzone są sukcesywnie z akwizycją próbek sygnałów pomiarowych, bez gromadzenia ich w pamięci, przy zachowaniu wysokiej częstotliwości próbkowania. Wymaganej mocy obliczeniowej dostarcza układ FPGA. Do obliczania transformaty użyto pamięci wzorca sinusa umieszczonej w układzie FPGA oraz 4 identycznych bloków pracujących równolegle: mnożnika i akumulatora.
In the paper, a new concept of a vector voltmeter for the impedance spectroscopy analyzer is proposed. The voltmeter uses the digital signals processing method for determination of orthogonal parts of measurement signals. The Discrete Fourier Transform calculations are performed “on-the-fly”, successively with acquisition of measurement signals samples, without the need of storing samples in a memory, while assuring the high sampling frequency. The required processing power was supplied by a Spartan 3 FPGA chip. For Fourier transform calculation, the sine pattern stored in the FPGA and 4 identical block sets, a multiplier and an accumulator, were created by Core Generator and used. The previously used vector voltmeter solution was based on a DSP processor with additional circuits (CPLD chip, memories, buffers) and was replaced by a single FPGA chip solution. The selected FPGA offers enough resources and allows reducing the number of additional external components. The prototype of the proposed solution was realized using the FPGA evaluation board with an added module of A/D and D/A converters (Fig. 3). The analyzer was realized in a form of a virtual instrument, the control panel was created by software. The tests were performed on the reference resistors (Figs. 8 and 9). The prototype proved the concept. However, it requires further works. It is necessary to look for a more energy-efficient FPGA chip as well as to optimize the project in terms of powerconsumption minimization.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 8.

Tytuł:: Fast high-impedance spectroscopy method using sinc signal excitation
Autorzy:: Kowalewski, M.
Lentka, G.
Tematy:: impedance spectroscopy
sinc signal
Fourier transform
impedance analyzer; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Czytelnia Czasopism PAN
Powiązania:: https://bibliotekanauki.pl/articles/220740.pdf Link otwiera się w nowym oknie
Opis:: In this paper the method of fast impedance spectroscopy of technical objects with high impedance (|Z_x| ≥ 1 GΩ) is evaluated by means of simulation and a practical experiment. The method is based on excitation of an object with a sinc signal and sampling the response signals proportional to current flowing through and voltage across the measured impedance. The object’s impedance spectrum is obtained with the use of continuous Fourier transform on the basis of linear approximations between samples in two acquisition sections, connected with the duration of the sinc signal. The method is first evaluated in MATLAB by means of simulation. An influence of the sinc signal duration and the number of samples on impedance modulus and argument measurement errors is explored. The method is then practically verified in a constructed laboratory impedance spectroscopy measurement system. The obtained acceleration of impedance spectroscopy in the low frequency range (below 1 Hz) and the decrease of the number of acquired samples enable to recommend the worked out method for implementation in portable impedance analyzers destined for operation in the field.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 9.

Tytuł:: Badanie elektrod o zwiększonej pojemności elektrycznej w spektroskopii impedancyjnej cieczy słaboprzewodzących
The study of electrodes with enhanced capacitance in impedance spectroscopy of poorly conductive liquids
Autorzy:: Macioszek, Ł.
Tematy:: spektroskopia impedancyjna
elektroda pojemnościowa
impedancja
impedance spectroscopy
capacitive electrode
impedance; Pokaż więcej
Wydawca:: Stowarzyszenie Inżynierów i Techników Mechaników Polskich
Powiązania:: https://bibliotekanauki.pl/articles/154172.pdf Link otwiera się w nowym oknie
Opis:: W pracy podjęto próbę oceny elektrod o zwiększonej pojemności elektrycznej, które użyte w spektroskopii impedancyjnej cieczy słaboprzewodzących pozwoliłyby na uzyskanie mniejszych wartości mierzonego modułu impedancji. Wyniki przeprowadzonych badań wskazują, że zarówno poprzez użycie elektrod o gęstszym układzie ścieżek, jak i kształtach ścieżek opartych na fraktalach, możliwe jest osiągnięcie większej pojemności elektrycznej układu elektroda-badana ciecz, a co za tym idzie mniejszych wartości modułu mierzonej impedancji.
In the paper an attempt is made to evaluate the electrodes with enhanced capacitance which used in the impedance spectroscopy of poorly conductive liquids would ensure lower values of impedance modulus. Three capacitive electrodes with different trace shapes are evaluated: basic comb electrode (denoted by I, shown in Fig. 1), comb electrode with denser traces (II, Fig. 2) and electrode III (Fig. 3) with traces of fractal based shapes. The measurements were taken with the use of the Princeton Applied Research laboratory system for electrochemical impedance spectros-copy. The results of impedance modulus measurement of the fresh engine oil are illustrated in Fig. 4, while those of the used engine oil are shown in Fig. 5. The results of impedance modulus meas-urement of the diesel fuel (Fig. 6) and cooking oil (Fig. 7) are also presented in the text. It is visible that the value of the measured impedance modulus is lower for comb electrode II and fractal electrode III than that obtained with electrode I. Table 1 contains the summary of the measured impedance modulus percentage using electrodes comb II and fractal III related to the results of the meas-urements with electrode I (as 100%). The test findings show that both comb electrode with denser traces and the one based on fractal shaped traces can provide greater electrical capacity of the electrode - poorly conductive liquid system and this, as a result, leads to lower values of the measured impedance modulus.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 10.

Tytuł:: Ograniczenia cyfrowego przetwornika impedancji AD5933
Limitations of the digital impedance converter (AD5933)
Autorzy:: Macioszek, Ł.
Tematy:: AD5933
cyfrowy przetwornik impedancji
pomiar impedancji
digital impedance converter
impedance measurement; Pokaż więcej
Wydawca:: Stowarzyszenie Inżynierów i Techników Mechaników Polskich
Powiązania:: https://bibliotekanauki.pl/articles/154899.pdf Link otwiera się w nowym oknie
Opis:: W pracy podjęto próbę zbadania przydatności układu AD5933 do współpracy z czujnikami impedancyjnymi o charakterze pojemnościowym. Nakreślono główne ograniczenia przetwornika AD5933 wynikające z jego konstrukcji. Porównano wyniki pomiarów modułu impedancji dwójników równoległych RC otrzymane za pomocą układu AD5933 i miernika HP4284A. Wyniki badań wskazują, że błąd pomiaru modułu impedancji maleje wraz z zawężaniem przedziałów wartości mierzonych. Przy dopuszczalnym błędzie pomiaru sięgającym kilku procent, przetwornik AD5933 może być zastosowany w urządzeniu docelowym.
In the paper there is made an attempt to verify the suitability of using the AD5933 impedance converter with capacitive-type impedance sensors. For this reason the levels of measurement errors of an impedance varying in a wide range were determined. The structure (Fig. 1) and the principle of operation of the AD5933 converter are presented. There are described the main limitations resulting from its construction and the available current measurement in the AD5933 converter (without simultaneous measurement of voltage), which forces making the calibration measurement before the real measurement of an unknown impedance. The accuracy of the impedance modulus measurement of chosen parallel RC circuits by means of the AD5933 was examined by comparison with the results obtained with use of the precise HP4284A LRC meter. The values of resistance and capacitance in the exemplary circuits were selected in such a way that the resultant impedance modulus changed in the possibly wide range along with changes of the measurement frequency. The results of the tests made on three chosen RC circuits are presented in the text (Figs. 2 - 4). Fig. 5 shows the impedance modulus relative error. Based on the findings of the tests one can conclude that the impedance measurement error decreases as the ranges of the measured values become narrower. The AD5933 impedance converter can be used in a measuring system when assuming that the measurement error of a few percent is acceptable.
Dostawca treści:: Biblioteka Nauki

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