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Licensed Unlicensed Requires Authentication Published by Oldenbourg Wissenschaftsverlag April 17, 2021

Dynamic water fill level measurement using a phantom-dependent adaptive electrical capacitance tomography (ECT) method

Messung eines dynamisch veränderlichen Wasserfüllstandes durch Anwendung einer phantomabhängigen adaptiven elektrischen Kapazitätstomografie (ECT)-Methode
Christoph Kandlbinder-Paret ORCID logo, Alice Fischerauer and Gerhard Fischerauer
From the journal tm - Technisches Messen

Abstract

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 high permittivity of water compared to the low permittivity of the pipe wall. The adaptation scheme leads to nearly the same information as a full measurement of all 120 elementary capacitances but only requires the measurement of 30 % fewer capacitances. By detecting the fill level using a tomometric method, it can be determined within an uncertainty of 5 % FS.

Zusammenfassung

In der elektrischen Kapazitätstomographie (ECT) verbessert sich die Auflösung der rekonstruierten Permittivitätsverteilung mit der Anzahl der verwendeten Elektroden während die Anzahl der Kapazitätsmessungen und die Messzeit mit der Anzahl der Elektroden zunimmt. Um einen Kompromiss zwischen Auflösung und Messzeit zu finden, präsentieren wir ein phantomabhängiges Adaptionsverfahren, in dem zunächst grobe Messungen mit zusammengeschalteten Einzelelektroden durchgeführt werden, die einen synthetischen Elektrodenring mit wenigen, aber großen Elektroden darstellen. Das Konzept wurde getestet, indem Schwappen von Wasser in einem Rohr beobachtet wurde. Wir vergleichen die rekonstruierten Ergebnisse basierend auf acht synthetischen Elektroden, 16 Elementarelektroden, und über das Adaptionsverfahren, bei dem sowohl die acht synthetischen Elektroden als auch einige der Elementarelektroden beteiligt sind. Bei der Rekonstruktion wird der projizierte Landweber Algorithmus sowohl für Kapazitäten, die durch Finite-Elemente Simulationen bestimmt werden, als auch für gemessene Kapazitäten angewendet. Die Ergebnisse enthalten Artefakte, die dem Einfluss der hohen Permittivität von Wasser im Vergleich zur geringen Permittivität der Rohrwand zugeschrieben werden. Das Adaptionsverfahren führt zu fast der gleichen Information wie eine vollständige Messung aller 120 elementaren Kapazitäten, erfordert aber nur die Messung von 30 % weniger Kapazitäten. Durch die Bestimmung des Füllstands mit einer tomometrischen Methode kann dieser innerhalb einer Unsicherheit von 5 % FS bestimmt werden.

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Received: 2021-01-28
Accepted: 2021-04-01
Published Online: 2021-04-17
Published in Print: 2021-09-26

© 2021 Walter de Gruyter GmbH, Berlin/Boston

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