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Wirbelströme werden in der Mess- und Sensortechnik sehr erfolgreich benutzt, um berührungslos Risse und Abstände metallischer Halbzeuge zu bestimmen. Die Messung von Konturen ist mit diesem industrietauglichen Wirkprinzip bisher nicht realisiert worden. Hier werden häufig optische Messsysteme eingesetzt. Speziell bei glühenden Werkstücken oder bei Benetzung der Halbzeuge mit Bohremulsionen und Schneidölen steigt der Aufwand für den Einsatz optischer Systeme stark an. Messverfahren, die auf hochfrequenten Wirbelströmen basieren, sind aufgrund ihrer einfachen Aufbauten deutlich robuster und somit besser für diese Anwendung geeignet. Voruntersuchungen zeigten, dass mit dieser Methode schon kleine Geometrieabweichungen des Walzgutes von wenigen Mikrometern detektiert werden können. In diesem Beitrag werden zwei Möglichkeiten zur Messung der spektralen Impedanzbeeinflussung eines Messschwingkreises durch die Wirbelströme im Werkstück gegenübergestellt.
Rolling mills are continually improved and opti-mized by implementing innovative technology to decrease costs and scrap. Despite of the progressive automation and experience, some important process parameters can still not be determined with sufficient accuracy. As part of the research project PIREF, the velocity of the hot rolled rod shall be measured by using im-pedance analysis to estimate the volumetric flow rate of the mate-rial. For a high accuracy measurement of the impedance, a pow-erful VNA is used. To minimize errors in the measurement, caused by e.g. temperature drift, a correction of the measurement fre-quency is needed. This must be achieved without recalibration of the VNA to avoid faulty behavior of the online control. To solve this problem, an approach based on a polynomial regression is presented in this work.
In the field of producing hot-rolled steel bars and wires, hot rolling mills are incomplete or barely equipped with measuring technology for recording relevant process parameters. Therefore, there is a big potential to increase product quality and to decrease costs and scrap by improving process control establishing new sensor systems. One of these crucial parameters is the roll gap,which is investigated as part of the research project PIREF. In this paper an experimental setup for examining the roll gap during a rolling process is presented and based on these results different sensor arrangements are discussed.
The transurethral resection (TUR) is a standard technique in urological treatment procedures. Both, monopolar and bipolar electrosurgical systems, are used for TUR. Whereas electrical and physical processes in surgery surroundings are well understood for monopolar systems, there is no sufficient data base for the assessment of the processes with the use of bipolar systems. In this context a multi-electrode measuring system was developed to visualize the spatial potential distribution around bipolar electrosurgical devices as a first step to risk analysis. To simulate the anatomic surroundings of a transurethral surgery a cylinder filled with isotonic saline solution is used as a complexity reduced experimental environment. Investigations about time stability and a qualitative assessment of the experimental set-up show deviations of measured values less than 5%. This is sufficient for further analysis of calculated power loss density distributions based on measured potential distributions. The spatial potential distribution around a bipolar devices is presented by horizontal and vertical sections through the experimental environment.
Die transurethrale Resektion der Prostata (TUR-P) ist der Gold Standard für die endoskopisch-chirurgische Behandlung der Benignen Prostatahyperplasie (BPH). Unbekannt ist jedoch, ob bei der bipolaren TUR-P die Möglichkeit von elektrothermischen Verletzung von benachbartem nichtopertiertem Gewebe besteht. Grund hierfür könnten höhere Ausgangsleistungen der Chirurgie-Generatoren sein. Deshalb werden experimentell gemessene Werte der räumlichen Verlustleistungsdichte um ein bipolares Resektoskop als Quellterm für die Berechnung der Temperaturänderung im operationsnahen Gewebe verwendet. Die Temperaturberechnung basiert auf der numerischen Lösung der Wärmeleitungsgleichung nach Penne. Für die gewählten Randbedingungen und Eingabeparameter sind keine signifikanten Temperaturerhöhungen im Berechnungsgebiet am proximalen Ende des Resektoskop-Schaftes festzustellen. Um ein umfassendes Verständnis zu gewinnen sollen weiterführende Untersuchungen mit einer Variation der Randbedingungen und Eingabeparameter durchgeführt werden
The bipolar transurethral resection is a further development of monopolar transurethral resection, being the gold standard in surgical treatment of prostate and bladder diseases. To create the metrological basis for understanding of electrical and physical processes during bipolar transurethral resection an experimental set-up to visualize spatial potential distribution around bipolar devices was developed. A hardware based signal conditioning and specific undersampling are presented as data acquisition methods for a sampling rate up to 1 MS/s. These methods are compared with the possibilities of a high speed data acquisition card. For more than four measuring channels and depending on the output bandwidth of the electrosurgical generator either hardware based signal conditioning or specific undersampling is suggested.
The harmonic and interharmonic analysis recommendations are contained in the latest International Electrotechnical Commission (IEC) standards on power quality. Measurement and analysis experiences have shown that great difficulties arise in the interharmonics detection and measurement with acceptable levels of accuracy. In this paper, the spectral leakage problems of the discrete Fourier transform due to synchronization errors of interharmonics are analyzed. The time-domain averaging is investigated for the processing of harmonics in the framework of the IEC standards. A difference filter is proposed to detect interharmonics and can be compatible with the IEC standards. Simulations and the field results show the usefulness of the proposed methods.
Fat content of liver is an essential parameter to decide whether a liver is suitable for transplantation or not. The determination of fat content is often challenging and usually there is not enough time to bring a specimen to a pathologic laboratory. That is why transplantation clinics need a technique to measure the fat content of a graft. In this paper the theoretical basics and an existing laboratory setup are presented.