Uwe Tröltzsch

Influence of surface effects on the characteristic curves of detergent sensors

The dynamic investigation of detergent properties during a washing process requires a sensitive measuring procedure, e.g. impedance spectroscopy. High selectivity and reproducibility are necessary to understand these properties. To keep down cross-sensitivity and interference, high requirements are demanded from the sensor element. The aims are to develop a sensor element which fulfills these requirements and to investigate the side-effects. Unavoidable cross-sensitivities and interferences will be described and eliminated as errors of measurement.

Analysis of the parameters of a lossy coaxial cable for cable fault location

This paper presents an estimation of the per-unit-length parameters of a lossy cable. A RLGC lumped element model for the lossy transmission line parameters of a coaxial cable including frequency dependent filtering effect is used in this study to evaluate reflectometry responses of the cable systems. The simulated results of this model are compared with the measured results of a coaxial cable using impedance spectroscopy to show the accuracy in frequency domain. This lossy transmission line model then is solved in the time domain to accurately locate the faults. The simulated results are compared with the measured results using time domain reflectometry. Finally this model is used to simulate branched cable networks.

Calculation of the distribution of relaxation times for characterization of the dynamic battery behavior

Impedance spectroscopy is widely used for characterization of batteries. Beside model based approaches for data analysis, the impedance spectra can be used to calculate a distribution of relaxation times (DRT). These DRT spectra can be seen as the time domain representation of the linear battery behavior as it describes the relaxation for different time constants. In contrast to the impedance spectra, it can be used to directly simulate the linear response of the battery. In this paper a calculation method for the distribution of relaxation times is shown that employs an iterative regularization scheme combined with stochastic methods for determination of the regularization parameters. For preserving peaks in the relaxation spectra during calculation edge preserving techniques are implemented.

Assessment of beef meat aging using impedance spectroscopy

The aim of the paper is to assess the feasibility of impedance measurements for meat aging detection. The carried investigations are dedicated to the aging of the meat of beef. An investigation was carried out for the detection of the age of meat using 2 cases of storage in the fridge, unpacked meat, exposed in the air of the fridge (Up) and vacuum-packed meat, conserved in closed box (Vp). The measurements show a depressed semicircle in the admittance plane similar to the equivalent circuit consisting of a combination of a Constant Phase Element (CPE) and two resistors. The resistance RE various is directly proportional to meat volume resistivity. The volume resistivity is constant for Vp meat, this is due to the conservation of the same situation in the surface of contact with the electrode, this situation change for the Up meat, the volume resistivity is increasing in a linear way because the surface of contact with electrode become more dry over time. The change due to Rct is inversely proportional to the factor number of electrons involved and exchange current. The factor n.i0 decreases over time for the Up meat, This is consistent because when the meat becomes drier, the loss of liquids causes the decrease of conductivity and proportionally the decrease of the number of electrons involved and the exchange current. For the second case (Vp), the humidity causes the decrease of the number of electrons involved and the exchange current. The impedance is inversely proportional to the double layer capacitance that is consistent with the experiments. The impedance increase for the Up meat and decrease in the second case. The change due to Cdl is directly proportional to the change of meat permittivity εr.

Diagnose von Gerätebatterien mit Impedanzspektrometrie (Diagnosis of Portable Secondary Batteries by Impedance Spectroscopy)

Abstract Zur Charakterisierung von Alterungseffekten von Gerätebatterien ist Impedanzspektroskopie eine der aussichtsreichsten Methoden, insbesondere bei der Trennung verschiedener Alterungseffekte. Bei einem breiten Einsatz der Impedanzspektroskopie im Online-Betrieb ergeben sich spezielle Anforderungen. Messzeiten müssen trotz niedriger Frequenzen kurz sein, was durch die Verwendung mehrfrequenter Signale erreicht wird. Modelle müssen mit verschiedenen Batterietypen verwendbar sein, weshalb Modelle von Mischelektroden Anwendung finden. Die Modellparameter müssen ohne Nutzerinteraktion bestimmt werden, daher wird eine Kombination von Evolutionären Verfahren und dem Levenberg-Marquardt-Algorithmus verwendet. Experimentelle Untersuchungen an einer Lithium-Ion-Zelle zeigen die Eignung der Impedanzspektroskopie zur Charakterisierung von Alterungseffekten. Eine Verringerung der Kapazität um 14% nach 230 Entlade-/Ladezyklen sowie eine Veränderung des Elektrolytwiderstandes, des Durchtrittswiderstandes und des Warburgkoeffizienten um jeweils etwa 60% wurden beobachtet.

Modellierung der absoluten Impedanz einer Luftspule mit Wirbelstromrückwirkung

Zusammenfassung Die analytische Modellierung von Spulenimpedanzen stellt die theoretische Grundlage vieler Wirbelstrommessverfahren dar. Wenn permeable Materialien untersucht werden, ist nicht nur die wirbelstrombedingte Impedanzänderung von Interesse, sondern auch die Relation dieser Änderung zu dem absoluten Wert. Feldmodelle auf der Grundlage des magnetischen Vektorpotentials wurden bereits zur Berechnung der wirbelstrombedingten Impedanzänderung benutzt. Durch Konvergenzprobleme bei der Integration lässt sich diese Berechnungsmethode nicht exakt auf den materialunabhängigen Impedanzanteil übertragen. In diesem Artikel wird die Ursache dieser Konvergenzprobleme gezeigt und über die Methode der Inneren und Äußeren Induktivität gelöst. So kann das bisherige Modellierungsverfahren um den materialunabhängigen Anteil auf eine ganzheitliche Impedanzbeschreibung erweitert werden. Eine ganzheitliche Modellierung umfasst alle betragsmäßig relevanten Impedanzanteile und liefert ein Maximum an Information aus den einzelnen Impedanzspektren. Die Leistungsfähigkeit dieses Verfahrens wird im anwendungsrelevanten Frequenzbereich von 10 kHz bis 10 MHz demonstriert, wobei berechneten Werten Versuchsdaten gegenübergestellt werden. Abstract The analytical modeling of coil impedances is a fundamental task for the design of antennas and eddy current sensors in different application fields. Not only changes of impedance but also the absolute values of the coil impedances are important because they provide a more detailed approach for magnetic material and coil characterization. Magnetic vector potential methods can give an accurate modeling of the magnetic field taking into account eddy current effects. Due to convergence problems during impedance calculation only the change of impedance is obtainable by the magnetic field model itself. These convergence problems can be explained and overcome by applying the concept of the internal and external inductance. In this paper we extent existing analytical impedance modeling techniques from differential impedance models to absolute impedance models. The provided model gives an analytical formula for coil impedances including eddy current influence in the target as well as in the coil itself. With the absolute impedance model available, the maximum of information can be extracted from the measured impedance spectra. The calculated results are compared to experimental values in the frequency range of 10 kHz to 10 MHz.

Implementierung der Impedanzspektroskopie in vollautomatischen Messsystemen am Beispiel der Batteriezustandsdiagnose (Battery Diagnosis as an Example for Implementing Impedance Spectroscopy in Automated Measurement Systems)

Die Impedanzspektroskopie wird im Labor erfolgreich für viele Anwendungen genutzt. In einer Laborumgebung können Einzelschritte durch die Intervention von Spezialisten interaktiv unterstützt werden. Für den Einsatz in vollautomatischen Messsystemen bestehen höhere Ansprüche. Im Beitrag wird am Beispiel der Batteriezustandsdiagnose dargestellt, durch welche Maßnahmen ein vollautomatisches Messsystem unter Nutzung der Impedanzspektroskopie realisiert werden kann. Schwerpunkte im Beitrag liegen auf der automatisierten Konsistenzprüfung von Messdaten mit einer praxisrelevanten Realisierung der Kramers-Kronig Transformation, der Gestaltung von Modellen und der Gestaltung des Optimierungsproblems. Vergleichbarkeit und Eindeutigkeit relevanter Parameterwerte von Impedanzmodellen grundlegender Mechanismen werden durch Eliminieren von Mehrdeutigkeiten und Normierung der Impedanzmodelle erreicht. Für die automatische Modellparameterextraktion wird vorgeschlagen, die Modellparameter durch Anpassung von Teilmodellen an automatisiert ermittelte Wirkungsbereiche zu extrahieren. Impedance spectroscopy is successfully used in laboratory environments where all necessary steps are performed by specialists. Requirements for fully automated measurement systems are more sophisticated. This paper discusses aspects for implementing impedance spectroscopy within fully automated measurement systems based on the example of battery diagnosis. It focuses on consistency check of measurement data by applying Kramers-Kronig Transform, design of impedance models and design of the optimization problem. Eliminating ambiguity and standardization of impedance models allows comparing relevant parameters of models for fundamental mechanisms. An automated model parameter optimization is supported by using different models for each frequency band with its dominating mechanisms. Frequency bands are determined from characteristical patterns within measurement data.

Modeling of single turn coil impedance including wiring effects

Because of their robustness, eddy current sensors are widely used in harsh environments. For the extraction of measurement quantities such as distances or material properties, a proper understanding of the magnetic filed distribution and of the impedance of the sensor is required. Thereby the calculation of the absolute impedance of eddy current sensors is still a difficult problem, because many analytical models in literature only allow the calculation of the impedance change due to a target material, but not the absolute impedance. Furthermore, models using geometry discretization for the calculation of absolute impedance values require long calculation times. In this contribution, an analytical impedance model for the calculation of the absolute impedance of a single turn coil is discussed. The impedance model is based on the magnetic vector potential. It allows the fast calculation of the impedance and does not require any methods for geometry discretization. Special efforts are made to analyze the effects of wiring. Wiring effects due to the coil wire itself and the connection wire are considered. A very good agreement between model and measurement is observed.