Papers by Alice Fischerauer
Design of Switcliable Iiiliiie Filters ailcl Compensation of Second Order
This paper discusses the compensation of serontl orcler effects of a filter structure wliicli pro... more This paper discusses the compensation of serontl orcler effects of a filter structure wliicli provides ditTereiit transfer functions by operating two or more traiistliicers in parallel, thereby adding or sul>tracting the respective transmissions in order to ohtain the tlesired functions. For each resulting transfer function, the diffraction and the circuit effects are cornpensated. The various possibilities of designing this switcliahle filter are discussed and a cornparison between analysis and measurement of a cornpensated st ruct we is presented.
Machine learning approach for impedance locus uncertainties
Tm-technisches Messen, Jun 22, 2023
This work deals with the determination of the uncertainty of measurement data, determined by elec... more This work deals with the determination of the uncertainty of measurement data, determined by electrical impedance spectroscopy. Four different types of sand were measured impedimetrically in a measuring cell designed as a plate capacitor in a frequency range from 20 Hz to 1 MHz. The measuring cell was filled ten times with each sand and 20 impedance spectra were recorded for each filling. The uncertainty at each frequency was determined from the measurement data. It was found that the measurement data variance with a given measuring-cell filling was negligibly small. However, it increased by a factor of up to 100 when the measuring cell was repeatedly emptied and re-filled with the same material. We propose a way to estimate a continuous approximation of the uncertainty band of the impedance locus in the complex plane from the discrete uncertainties at each frequency. It uses a Support Vector Machine (SVM) to generate a regression curve using the discrete uncertainties. The result of the regression was used to estimate the uncertainties of an average impedance locus. The said machine learning tool can handle large amounts of data, classes, and influencing variables. In this manner, it can help to identify cause-effect relationships. Furthermore, at the end of this work a possibility to estimate a continuous uncertainty band along the impedance locus curve via SVM regression is shown. This is an extension to the common methodology in literature, where the uncertainty is only determined at selected individual points of the impedance spectrum.
A novel physics-based impedance model of Cr2O3/zeolite-coated chemocapacitors
Bridges, being concrete structures, oscillate from excitation with impulsive forces. The details ... more Bridges, being concrete structures, oscillate from excitation with impulsive forces. The details of these oscillations such as amplitudes, frequencies, and their decay coefficients bear information about the structural health of the bridge. Each tire of a passing vehicle excites the bridge with a short impulse of force, which contains a broad frequency spectrum. We developed a mathematical model to describe the resulting oscillations and compared the time response of the model with measurements taken at the deck of a bridge.
Acoustic multiplexing by beamsteering for SAW chemical multisensors
2016 IEEE International Ultrasonics Symposium (IUS), 2016
A new concept for designing an integrated chemical multisensor with only two ports based on surfa... more A new concept for designing an integrated chemical multisensor with only two ports based on surface acoustic waves is presented. Following a principle from antenna theory an acoustic group antenna is assembled consisting of a number of identical interdigital transducers that are fed with currents of equal amplitude, but with a phase difference between neighbors. The propagation of the wave launched by such an antenna is investigated through simulation of the associated surface potential. In order to validate the concept and the simulation arrays with up to ten element-IDTs are built and the distribution of the periodic displacement of the substrate surface is observed by laser interferometry.
Mikrosensor für gleichzeitige Feuchte- und Temperaturmessung mit dreidimensional strukturierten Interdigitalelektroden
IEEE Workshop on Industrial and Medical Measurement and Sensor Technology – SENSORICA 2016
tm - Technisches Messen, 2017
On June 16th and 17th, 2016, the highly successful lecture series on measurement and sensor techn... more On June 16th and 17th, 2016, the highly successful lecture series on measurement and sensor technologies as part of the IEEE Workshop at the Institute for Measurement and Sensor Technology at the University of Applied Sciences Ruhr West (HRW) was continued in collaboration with the Institute of Thermodynamics at the University of Siegen, the Chair of Measurement and Sensor Technology at the Technical University of Chemnitz and the ITMO National Research University of Information Technologies, Mechanics and Optics in St. Petersburg, Russia. This time the event featured an even more international orientation by linking it with the Russian SENSORICA. The topics of the 36 contributions to the workshop covered sensor technology in vehicles as well as industrial and medical measurement technology. Eight topics were chosen for this special issue. One half of them are focused on the field of medical measurement techniques such as magnetic resonance imaging, optical tracking for minimal-invasive surgery, exact preoperative planning in hip surgery and an approach for a telemetric multi-sensor system. The other half addresses the field of optical measurement systems applied to engine testing, LIBS for elemental analysis, IR-based quantitative measurement of complex substances in liquids and the analysis of wavefront structures of diode lasers. Our workshop again offered a platform for knowledge transfer between industry and public as well as commercial research institutions in the area of measurement technology.
Surface wave dual converter for a dual filter in particular for television sets
A Physics-Based Model for the Impedance Spectrum of an Interdigital Capacitor Covered by Functional Layers
Planar interdigital capacitors (IDC) covered with a thin Cr 2 O 3 layer and a zeolite thick film ... more Planar interdigital capacitors (IDC) covered with a thin Cr 2 O 3 layer and a zeolite thick film are known to act as gas sensors. Until now, their impedance behavior has been modeled by equivalent circuits involving constant-phase elements (CPE) with a poor physical justification. We present a physical model for the sensor impedance which is based on the underlying atomistic processes.
Design of switchable inline filters and compensation of second order effects
IEEE 1992 Ultrasonics Symposium Proceedings
ABSTRACT The authors discuss the compensation of second-order effects of a filter structure which... more ABSTRACT The authors discuss the compensation of second-order effects of a filter structure which provides different transfer functions by operating two or more transducers in parallel, thereby adding or subtracting the respective transmissions in order to obtain the desired functions. For each resulting transfer function, the diffraction and the circuit effects are compensated. The various possibilities of designing this switchable filter are discussed, and a comparison between analysis and measurement of a compensated structure is presented
A novel highly sensitive SAW strain sensor with in-built temperature measurement
2012 IEEE International Ultrasonics Symposium, 2012
ABSTRACT In this contribution, we describe a novel temperature-compensated SAW strain sensor for ... more ABSTRACT In this contribution, we describe a novel temperature-compensated SAW strain sensor for remote sensing. Temperature is the most important disturbance variable in SAW sensors, and this motivates the search for methods to suppress the temperature influence. The sensor design proposed consists of two SAW structures each comparable to a delay line and exploits electrical loading and multiple-transit signals. The interdigital transducers (IDTs) are connected in a way that leads to a sensor signal with a frequency spectrum showing a certain number of minima depending on the distances between the IDTs. The frequencies of these minima are influenced by both strain and temperature. Their evaluation allows to extract a temperature compensated strain signal with a resolution of about 10 ppm.
Physikalisches Modell der Materialparameterabhängigkeit des Impedanzspektrums planarer Chemosensoren in Mehrschichtbauweise
tm - Technisches Messen, 2011
Zusammenfassung Planare Chemosensoren bestehen häufig aus Interdigitalelektroden (IDE), die auf e... more Zusammenfassung Planare Chemosensoren bestehen häufig aus Interdigitalelektroden (IDE), die auf einem Substrat aufgebracht und in mehrere Schichten von Funktionsmaterialien wie Metalloxiden oder Ionenleitern eingebettet wurden. Die Impedanzen solcher Sensoren weisen untereinander ähnliche, charakteristische Spektren auf, was auf ein gemeinsames zugrunde liegendes Funktionsprinzip hindeutet. Zur quantitativen Erfassung der Sensorimpedanz bedarf es daher eines physikalischen Modells, das den Zusammenhang zwischen der Sensorimpedanz und den Materialparametern der eingesetzten Schichten, der Geometrie und der Betriebstemperatur beschreibt. Ausgehend von den Methoden der klassischen Halbleitertheorie wird in der vorgestellten Arbeit der durch den Sensor tretende Strom berechnet. Dabei wird der Einfluss eventuell vorhandener beweglicher Ionen durch eine elektrostatische Näherung beschrieben. Aus den ersten Harmonischen der zeitvariablen Bauteilspannung und des Bauteilstromes lässt sich da...
IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, 1993
Dynamic water fill level measurement using a phantom-dependent adaptive electrical capacitance tomography (ECT) method
tm - Technisches Messen
In electrical capacitance tomography (ECT), the resolution of the reconstructed permittivity dist... more In electrical capacitance tomography (ECT), the resolution of the reconstructed permittivity distribution improves with the number of electrodes used whereas the number of capacitance measurements and the measurement time increases with the number of electrodes. To cope with this tradeoff, we present a phantom-dependent adaptation scheme in which coarse measurements are performed with terminal electrodes interconnected to form a synthetic electrode ring with fewer but larger electrodes. The concept was tested by observing the sloshing of water inside a pipe. We compare the reconstructed results based on eight synthetic electrodes, on 16 elementary electrodes, and on the adaptation scheme involving both the eight synthetic electrodes and some of the elementary capacitances. The reconstruction used the projected Landweber algorithm for capacitances determined by a finite-element simulation and for measured capacitances. The results contain artefacts attributed to the influence of the ...
Journal of Sensors and Sensor Systems, Oct 11, 2022
This work deals with the impedimetric monitoring of used-sand regeneration in the foundry industr... more This work deals with the impedimetric monitoring of used-sand regeneration in the foundry industry. During the regeneration of used sand, a quartz sand similar to new sand is produced from already used molding and core sand, which especially serves to produce new cores. We explore whether the regeneration progress can be assessed in situ based on measured impedance spectra and their features. The impedances of plate capacitors filled with different typical used-sand mixtures, consisting of quartz sand, coal dust, and bentonite, were repeatedly measured in a frequency range from 500 Hz to 1 MHz. The reproducibility of the measurements proved to be sufficient for practical applications. The mean impedances were plotted in Nyquist diagrams. From these plots, systematic impedance-composition correlations could be determined for two of the three component systems. Conclusions about the regeneration state could be drawn from the impedance curves by introducing various features. These were the median, the mean, and the standard deviation of the frequency-dependent resistance and reactance. With these indicators, it was then possible to establish one-to-one relations between the material composition of the molding materials and the impedance measurement. In field measurements on regenerated used sands, this observation was confirmed, and the regeneration progress was observed on the basis of the impedimetrically determined characteristic data.
Journal of Sensors and Sensor Systems
The global economy consumes an estimated 4 × 10 10 t of sand per year, with only 2 × 10 10 t of s... more The global economy consumes an estimated 4 × 10 10 t of sand per year, with only 2 × 10 10 t of sand being reproduced by natural sedimentation (Götze and Göbbels, 2017; Peduzzi, 2014). Among other things, sand is also used as a basic material for the production of molds and cores in the foundry industry. The consumption and the economic as well as ecological savings' potential in this area of application can be appreciated by way of an example: the environmental certificate of a single, albeit big German foundry (5160 employees) can be consulted, which states that 39 820 t of sand for casting molds had to be purchased in 2017 (Denes, 2018). In order to avoid having to dispose of the used sand in landfills and to reduce the use of new sand, it is therefore advantageous to renew the used sand in a so-called regeneration process and reuse it as a substitute for new sand in the production of molds and cores. It would be very advantageous if the condition of molding materials (sandbinder systems) in regenerator units could be monitored in real time because of the economic and ecological advantages of a monitored and optimized regeneration process. This work presents the results of investigations in this direction. The objects of investigation in this work are typical molding materials in the foundry industry, e.g., quartz sand, chromite sand, and bentonite as a binder, which are measured impedimetrically with the help of a plate capacitor measuring cell which is connected to an LCR meter (Agilent E4980A). The impedance of the filled capacitor is measured in a frequency range from 1.2 kHz to 1 MHz, containing 123 frequency points. The aim of this research is to work out if the mentioned substances can be measured with the presented measuring method and classified on the basis of impedance characteristics and thus whether impedance spectroscopy can be considered for process monitoring in the molding industry. It is shown that the condition monitoring can possibly be based on impedance spectroscopy because the resulting curves are characteristic of the material used. New and used sands as well as two-component mixtures of sands and binders showed a systematic behavior, which allows the sand or the composition of the mixture to be identified (classified) in the future. The examination of the scatter of the measurement results shows that the impedance data obtained with this method can be measured reproducibly. A descriptive model for multi-component systems is developed in order to be able to interpret the impedance scatter results and their representation in Nyquist plots. From this model, the filling density of the measurement cell and the density of conduction paths can be extracted as essential influence quantities.
Investigation of complex permittivity spectra of foundry sands
tm - Technisches Messen
This paper discusses impedance spectroscopy as a method to characterize different types of quartz... more This paper discusses impedance spectroscopy as a method to characterize different types of quartz sand, chromite sand, and mixtures of sand. Based on two types of measurement cells, the impedance spectra for various dry sands were measured. The spectra differ enough to allow the sands to be distinguished. The results were validated by extracting the relative permittivity from the impedance and comparing it to literature data. After that, the method could be applied with confidence to other material systems. The influence of moisture was investigated with two types of quartz sand, and typical mixtures of form sand, chromite sand, and regenerated (quartz) sand were studied. In each case, the sand composition had a distinct influence on the Nyquist plot of the impedance spectrum. Compared to results from a laboratory foundry system, the new method exhibits a much more systematic dependence on the sand composition. If one succeeds in describing the impedance spectra with an equivalent c...
Raw impedance data for MUT 1 to 6 and evaluation data for SVMs
Detection of Bubbles in Cryogenic Liquids using Electrical Capacitance Tomography
Uploads
Papers by Alice Fischerauer