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In the field of magnetic inductance tomography,
signal processing is a real challenge. This is due to the divergent
nature of magnetic fields. The sensitivity, i.e. the change in the
receiving signal by means of an electrically conductive sample
in a measuring volume depends strongly on the positioning
of the sample. Objects that are located near the transmitting
or receiving coils are very well locatable, where objects in
larger distance are hard to detect. In this paper an approach
is presented that improves the topology of the magnetic fields
in the ”magnetic induction tomography” (MIT) by changing
geometric constructions and current patterns of coils so far,
as to allow a sharper localization of objects within the space.
The aim is to level the distribution of the sensitivity in the
measuring volume, so that electrically conductive objects with
a larger distance between transmitting and receiving unit can
be detected with almost the same signal intensity as objects
close to the transmitting and receiving unit. The simulation tool
Comsolic is used for the geometric modeling making a finite
element analysis (FEA). The subsequent signal processing and
analysis of the simulation results are implemented in Matlabic .
Within this FEA the coil geometries and current patterns are
changed numerically, so that the minimum object size, that is
still detectable, is, compared to the known MIT, reduced and the
sensitivity of the system is improved. To validate the simulation in
Comsolic , first simulation results are compared with analytical
models and analyses.
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.
Influencing Parameters on Measuring the Cross-Section Area of Hot Rolled Rods in Steel Industries
(2014)
Wirbelstromsensoren sind in der industriellen Messtechnik stark verbreitet. Insbesondere bei der Herstellung warmgewalzter Halbzeuge können sie durch ihre Robustheit gegenüber Wasserdampf und hohen Walzguttemperaturen überzeugen. Ein noch offenes Feld ist die In-Situ‐Detektion von Rissen im Draht während des Walzprozesses bei Walzgeschwindigkeiten bis zu 100 m/s und Materialtemperaturen bis zu 1200 ℃. Im Folgenden soll mittels der Finiten-Elemente-Analyse untersucht werden, wie sich Längsrisse im Draht auf Oberflächenströme und damit auf deren magnetische Flussdichte auswirken. Ziel ist es, Aussagen über den Einfluss verschiedener Rissbreiten und Risstiefen auf die magnetische Flussdichte zu machen und so einen möglichen Effekt auf einen Wirbelstromsensor untersuchen zu können.