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EN
In recent years, smog and poor air quality have become a growing environmental problem. There is a need to continuously monitor the quality of the air. The lack of selectivity is one of the most important problems limiting the use of gas sensors for this purpose. In this study, the selectivity of six amperometric gas sensors is investigated. First, the sensors were calibrated in order to find a correlation between the concentration level and sensor output. Afterwards, the responses of each sensor to single or multicomponent gas mixtures with concentrations from 50 ppb to 1 ppm were measured. The sensors were studied under controlled conditions, a constant gas flow rate of 100 mL/min and 50 % relative humidity. Single Gas Sensor Response Interpretation, Multiple Linear Regression, and Artificial Neural Network algorithms were used to predict the concentrations of SO2 and NO2. The main goal was to study different interactions between sensors and gases in multicomponent gas mixtures and show that it is insufficient to calibrate sensors in only a single gas.
2
Content available remote Adsorption and gas sensing properties of CuFe2O4 nanoparticles
EN
Spinel ferrite nanoparticles in the form CuFe2O4 were tested for gas sensing applications. Nanoparticles pressed in a disk form were used to construct conductometric gas sensors. The disk was placed between two electrical electrodes wherein the top electrode had a grid structure. The produced sensors were tested against H2S and H2 gases and they were found to be selective and sensitive to H2S concentration as low as 25 ppm. The composition of the nanoparticles was confirmed by X-ray diffraction and energy dispersive X-ray spectroscopy measurements. The crystal structure was verified by both X-ray diffraction and transmission electron microscope. The observations obtained from the experiments demonstrated the high potential of using CuFe2O4 nanoparticles for H2S sensing applications.
EN
The paper presents a numerical method of dynamic error correction applied to a measuring transducer of gas concentration with a typical sensor based on tin dioxide. The work describes research of the dynamic properties of the transducer. Its response time is approximately 8 to 10 minutes, which may be not acceptable in many applications. A parametric model of the transducer dynamics has been developed and an adequate correction algorithm is proposed. The obtained results of the dynamic correction based on the proposed method are compared with those achieved previously by applying a neural network algorithm. Despite the simplicity of the used model, the proposed method allows a significant decrease in the transducer response time.
EN
Nanocrystalline ZnO-TiO2 (with molar ratios 9:1, 7:3, 1:1, 3:7 and 1:9) were successfully synthesized by hydrothermal method. Synthesized materials were examined with the help of X-ray diffraction and transmission electron microscope. Liquid petroleum gas sensing characteristics of the ZnO-TiO2 films were investigated at different operating temperatures. The ZnO-TiO2 thick film (with 1:1 molar ratio) exhibited good response toward liquid petroleum gas as compared to other investigated compositions. Further, liquid petroleum gas sensing characteristics of CuO modified ZnO-TiO2 thick films were investigated. 0.2 M CuO modified ZnO-TiO2 thick film exhibited excellent liquid petroleum gas sensing characteristics such as higher response (~ 1637.49 at 185 °C) with quick response time (~30 s), low recovery time (~70 s), excellent repeatability and stability at low operating temperature.
6
Content available remote MWCNT-Pt nanocomposite as the active element of harmful gas sensors
EN
Purpose: The goal of this paper is presentation of the variations in MWCNTs-Pt nanocomposite resistance which were examined in the presence of hydrogen with a rising concentration of, respectively, 1, 2, 3 and 4% H2 as well as nitrogen dioxide with a rising concentration of, respectively, 20, 100, 200, 400 ppm of NO2. Design/methodology/approach: Variations in electrical conductivity for the MWCNTs-Pt composite placed, alternately, in the atmosphere of gas and in the atmosphere of selected gases, were measured with a measuring station equipped with precision and inert gas reducers, mass flow meters, filtration systems of gas mixture and the studied mixture’s humidity and temperature control. An active layer of the transducer consisted of MWCNTsPt nanocomposite deposited thereon. All the measurements were carried out in the atmosphere of synthetic air (20% of O2 and 80% of N2) at 22.5°C. Findings: It was found based on the results obtained that system resistance is rising as hydrogen concentration is rising in the atmospheric air. The results of analogous examinations of variations in MWCNTs-Pt nanocomposite resistance carried out for a varying concentration of nitrogen dioxide in the atmosphere of synthetic air are opposite, because lowering system resistance was noted along with a heightening concentration of NO2. The best results were achieved for the nanocomposite presented in the article having a 5% mass concentration of platinum and with uniformly dispersed Pt particles on the surface of carbon nanoparticles. Practical implications: The outcomes presented signify the selectiveness of the applied system consisting of carbon nanotubes decorated with platinum nanoparticles. It means that this material can be used as the active element of harmful gas sensors. Originality/value: A carbon-metal MWCNTs-Pt nanocomposite with special electrical properties was fabricated in the course of research works, whose originality is based on the appropriately selected composition and the specific morphology.
EN
An array consisting of four commercial gas sensors with target specifications for hydrocarbons, ammonia, alcohol, explosive gases has been constructed and tested. The sensors in the array operate in the dynamic mode upon the temperature modulation from 350°C to 500°C. Changes in the sensor operating temperature lead to distinct resistance responses affected by the gas type, its concentration and the humidity level. The measurements are performed upon various hydrogen (17-3000 ppm), methane (167-3000 ppm) and propane (167-3000 ppm) concentrations at relative humidity levels of 0-75%RH. The measured dynamic response signals are further processed with the Discrete Fourier Transform. Absolute values of the dc component and the first five harmonics of each sensor are analysed by a feed-forward back-propagation neural network. The ultimate aim of this research is to achieve a reliable hydrogen detection despite an interference of the humidity and residual gases.
EN
The paper presents the results of an analysis of gaseous sensors based on a surface acoustic wave (SAW) by means of the equivalent model theory. The applied theory analyzes the response of the SAW sensor in the steady state affected by carbon monoxide (CO) in air. A thin layer of WO3 has been used as a sensor layer. The acoustical replacing impedance of the sensor layer was used, which takes into account the profile of the concentration of gas molecules in the layer. Thanks to implementing the Ingebrigtsen equation, the authors determined analytical expressions for the relative changes of the velocity of the surface acoustic wave in the steady state. The results of the analysis have shown that there is an optimum thickness of the layer of CO sensor at which the acoustoelectric effect (manifested here as a change in the acoustic wave velocity) is at its highest. The theoretical results were verified and confirmed experimentally.
PL
W pracy omówiono najczęściej stosowane układy spektroskopii absorpcyjnej przeznaczone do wykrywania śladowych ilości niebezpiecznych gazów, par materiałów wybuchowych i wybranych biomarkerów w wydychanym powietrzu. Szczególną uwagę poświęcono układom z komórkami wieloprzejściowymi, metodzie CRDS (ang. Cavity Ring Down Spectroscopy) i jej odmianom. Omówiono problemy związane z absorpcją promieniowania podczerwonego przez parę wodną, oraz konstrukcją tego typu czujników w celu uzyskania możliwie jak największej czułości. Przedstawiono celowość stosowania układów służących do filtracji, osuszania oraz dostarczenia tak przygotowanej próbki do modułów zatężania (tzw. prekoncentratorów), a następnie do czujników.
EN
The paper presents laser absorption spectroscopy systems, which are the most commonly used for detection of trace hazardous gases, explosives vapors and the biomarkers in exhaled air. Particular attention was paid to the systems of multi-pass cells and cavity enhanced spectroscopy (CRDS, CEAS). Disadvantage influence of water vapor and carbon dioxide was analyzed. These gases occur in breath with high concentration, which cause a limitation of the sensitivity. The attempt to minimization of this effect and experimental results are also described.
PL
W artykule przedstawiono wyniki badań czujnika elektrokatalitycznym w atmosferze zawierającej chlor. Prezentowane badania dotyczą czujnika wykonanego w technologii ceramicznej na bazie NASICONu posiadającego dwie okrągłe, platynowe elektrody. Wykonano pomiary w różnych temperaturach w celu wyznaczenia optymalnej temperatury działania czujnika.
EN
In this paper performance of an electrocatalytic sensor in presence of chlorine is investigated. Presented studies concern sensor prepared in ceramic technology based on NASICON as a solid electrolyte with two round shaped platinum electrodes. Measurements in different temperatures have been performed in order to determine optimal sensor working temperature.
PL
W tej pracy przedstawiono wyniki badań amperometrycznego czujnika dwutlenku siarki z ciekłym elektrolitem, siarczanortęciową elektrodę odniesienia oraz elektrodę roboczą w postaci membrany wykonanej z polimerowego elektrolitu stałego (Nafionu) pokrytej złotem. Głównym celem przedstawionych badań było określenie wpływu składu elektrolitu wewnętrznego na właściwości czujnika. Przebadano czujnik wypełniony 1M i 5M kwasem siarkowym.
EN
In this work investigation of an amperometric sulphur dioxide sensor with a liquid electrolyte, a mercury sulphate reference electrode and solid polymer electrolyte (Nafion) covered with gold as a working electrode properties is presented. The main goal of this research is to determine the influence of internal electrolyte composition on the sensor properties. Sensor filled with 1M and 5M sulphuric acid has been studied.
EN
The paper deals with the investigations concerning the influence of the changing gas environment on electrical resistance of zinc oxide (ZnO) nanostructures. The investigated structures are wide-gap semiconductors with the morphology of ZnO flower-shaped agglomerates of nanostructures. The resistance changes of these nanostructures were tested under the influence of various gases such as nitrogen dioxide (NO2), hydrogen (H2), ammonia (NH3) and also of humidity changes of carrier gases. To clarify the mechanisms of physicochemical processes in ZnO nanostructures during their interaction with gaseous environments, investigations were performed in two different carrier gases, viz. in synthetic air and in nitrogen. The study was carried out at a structure temperature of 200◦C.
13
Content available remote Korekcja nieliniowości charakterystyk rezystancyjnych czujników gazów
PL
Półprzewodnikowe rezystancyjne czujniki gazów, pomimo wysiłku konstruktorów, wykazują szereg niekorzystnych właściwości metrologicznych, w tym znaczną nieliniowość charakterystyk przetwarzania. W artykule opisano metodę wyznaczania charakterystyki przetwarzania dla pewnej klasy czujników tego typu i przedstawiono uzyskane wyniki. Zaproponowano analogowy układ kondycjonowania pozwalający na kształtowanie charakterystyk przetwarzania części analogowej toru pomiarowego, a w szczególności uzyskanie znacznie lepszej liniowości w szerokim zakresie stężeń gazów. Zamieszczono zależności opisujące układ. Przedstawiono charakterystyki toru pomiarowego uzyskane przy zastosowaniu czujnika typu TGS 3870, przeznaczonego do zastosowań w miernikach stężenia tlenku węgla i metanu. Proponowany układ może znaleźć zastosowanie również dla innych typów półprzewodnikowych, rezystancyjnych czujników gazów.
EN
The transfer curves of gas sensors based on semiconductor sensing materials (like SiO2) usually are strongly nonlinear. The characteristics given in data sheets are not precise enough to design a transducer for gas concentration measurements, therefore an individual calibration of the sensor is needed. This paper describes a method of determination of the transfer curve for selected types of semiconductor resistive gas sensors. There is also presented an electronic conditioning device, designed to considerable improve linearity for the measuring transducer, composed of the sensor and conditioning device. This device was applied to TGS3870 sensor, which is sensitive to carbon monoxide and methane. Linearity of transfer curves is considerably better in comparison with that ones for the sensor.
PL
Czujniki wykrywające wodór i inne gazy w oleju działają na różnych zasadach, co stanowi o ich zaletach i ograniczeniach. Dotychczas głównym ograniczeniem powszechnego zastosowania układów monitorujących zawartość gazów w oleju była wysoka cena. Opracowanie układu monitorującego w oparciu o palladowy czujnik zawartości oleju uprościło konstrukcję i obniżyło cenę takiego układu do poziomu uzasadniającego jego stosowanie do transformatorów średniej mocy.
EN
Gas in oil monitoring devices for condition assessment of HV power-transformer insulation have been reviewed for their measuring characteristics, complexity of design and cost. More advanced, complex and expensive monitors have been installed on large and strategically important transformers. However, the medium-power transformers constitute majority of transformer population in electric-power systems, but the high price of monitoring devices prevented their application to the medium-power units. The recently designed inexpensive Hydrogen-in-oil monitor uses a Palladium alloy sensor that reduces complexity and cost of this monitor effectively. Installation of such a simple monitoring system on medium-power transformers is economically justified, in particular on units with service-aged paper-oil insulation. The paper describes on-line diagnostics of power transformers with various measuring devices. Such diagnostics is based on measurements of hydrogen, carbon oxides, gas chromatography, photo-acoustic gas spectrography.
15
Content available remote Gas sensing performance of nanocrystalline ZnO prepared by a simple route
EN
The nanocrystalline powders of pure and Al3+-doped ZnO with hexagonal structure were prepared by a simple hydrothermal decomposition route. The structure and crystal phase of the powders were characterized by X-ray diffraction (XRD) and the microstructure by transmission electron microscopy (TEM). All the compositions exhibited a single phase, suggesting a formation of solid solution between Al2O3 and ZnO. DC electrical properties of the prepared nanoparticles were studied by DC conductivity measurements. The indirect heating structure sensors based on pure and doped ZnO as sensitive materials were fabricated on an alumna tube with Au electrodes. Gas-sensing properties of the sensor elements were measured as a function of concentration of dopant, operating temperature and concentrations of the test gases. The pure ZnO exhibited high response to NH3 gas at an operating temperature of 200 C. Doping of ZnO with Al3+ increased its response towards NH3 and the Al3+-doped ZnO (3.0 wt% Al2O3) showed the maximum response at 175 C. The selectivity of the sensor elements for NH3 against different reducing gases like LPG, H2S and H2 was studied. The results on response and recovery time were also discussed.
EN
H2S and SO2 are important characteristic gases reflecting latent insulated defects in gas insulated switchgear (GIS).The detection of the H2S and SO2 is of great significance to diagnose and assess the operating status of GIS. In this paper, the single-walled carbon nanotubes (SWCNTs) are modified by hydroxyl and carboxyl, respectively. The gas sensing response of the modified SWCNTs to H2S and SO2 are studied. The results show that the sensitivity of SWCNTs modified by carboxyl is higher than that of SWCNTs modified by hydroxyl to H2S, the same for SO2.
PL
Przedstawiono metodę detekcji H2S iSO2 jako możliwość oceny stanu izolacji przełączników gazowych GIS. Jako czujnik wykorzystano nanorurki węglowe SWCNTs modyfikowane przez wodorotlenki hydroxyl i carboxyl.
EN
In this paper, experimental investigations of carbon monoxide (CO) influence on organic materials, namely the plasma of human blood, natural proteins in egg white (albumin) and liquid crystal materials, are presented.
PL
W artykule opisano eksperymentalne badania wpływu tlenku węgla (CO) na wybrane materiały organiczne: osocze ludzkiej krwi i naturalne białko jaj (albuminę), oraz materiały ciekłokrystaliczne.
EN
For the purpose of this work TiO₂ : (V, Ta) thin films have been manufactured and characterized. Two types of performed measurements, that are conductometrical and thermoelectrical and differences between them have been especially discussed. Measurements of response and recovery times of Ti0₂ : (V, Ta) thin film gas sensor in the presence of isopropyl alcohol have been carried out. Optical properties, i.e. transparency and its changes in the presence of isopropanol have been also studied.
PL
W artykule przedstawiono wyniki badania wytworzonych cienkich warstw TiO₂ : (V, Ta). Wykonano pomiary konduktometryczne oraz termoelektryczne badanych cienkich warstw i omówiono różnice między nimi. Wyznaczono czasy odpowiedzi oraz odtrucia gazoczułych cienkich warstw TiO₂ : (V, Ta) dla pobudzenia parami alkoholu izopropylowego. Badano również zmianę właściwości optycznych cienkich warstw w obecności izopropanolu.
EN
In this study properties of Nasicon solid state gas sensors working in electrocatalytic mode are investigated. The principle of operation of such sensors is based on the excitation with a periodic potential signal, while current response is recorded. The sensors are prepared in ceramic technology with two different constructions. One construction is a symmetrical, sandwich type structure with electrolyte between two identical gold electrodes. In the second, the same structure is used, but the electrodes are covered with auxiliary layer of sodium nitrite. Nitrogen dioxide sensing properties of both sensors are determined and compared.
PL
W pracy zostały przedstawione wyniki pomiarów czujnika na bazie Nasiconu pracującego w trybie elektrokatalitycznym. Czujniki takie pobudzane są zmieniającym się napięciem przy jednoczesnym pomiarze odpowiedzi prądowej. Przygotowano czujniki ceramiczne o dwóch różnych typach. Pierwszy z nich to czujnik posiadający dwie identyczne elektrody złote, pomiędzy którymi znajduje się elektrolit stały. Drugi czujnik posiada złote elektrody dodatkowo pokryte warstwą azotanu (III) sodu. Zmierzono i porównano odpowiedzi obu czujników dla różnych stężeń dwutlenku azotu w mieszaninie z powietrzem.
PL
Rozważane są wybrane aspekty zastosowania dwuwymiarowych kryształów fotonicznych jako elementów aktywnych w optycznych czujnikach gazów. Działanie analizowanych czujników oparte jest na metodach spektroskopii absorpcyjnej. Możliwe do uzyskania w krysztale fotonicznym znaczące obniżenie prędkości grupowej światła, tzw. efekt powolnego światła (ang. slow light), podnosi efektywność oddziaływania pomiędzy falą świetlną a ośrodkiem gazowym.
EN
Selected aspects are discussed of two-dimensional photonic crystals to be applied as active elements of spectroscopic gas sensors. Absorption spectroscopy methods are employed in the sensors considered. Significant decrease in light wave group velocity, the slow light effect, obtainable in photonic crystals enhances the efficiency of the light-gas interaction.
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