C4.2 - Electrical Capacitance Tomography for Level Measurements of Separated Liquid Stacks

Abstract

The determination of liquid levels in industrial vessels of process plants or tanks in automotive applications is an important measurement task in a number of today’s industrial processes. Traditional level sensors are mechanical devices like floaters, hydrostatic pressure sensors, capacitive tubular sensors or ultrasound/radar based time of flight sensors. In a number of industrial processes the used fluids are mixtures or emulsions of different media. In tanks this emulsions separate due to the different densities of the components. In this case traditional sensors fail. Recently, the application of methods out of electrical capacitance tomography has been presented for noninvasive capacitive level sensors to determine stacked liquid layers [1]. Typically, noninvasive capacitive level sensors take use of the almost linear signal trend obtained by the different sensor segments when the liquid level is crossing the specific segment [2], [3]. Hence, the methods are not applicable for stacked liquid layers. However, the linear trend is also a matter of the arrangement of the electrodes. It has also been reported in [1], that for other electrode arrangements far more complex signal trends can be observed. Due to the complex signal trends, the application of more powerful model based algorithms to obtain phase boundaries between different immiscible fluids seems suitable. In this work we investigate the behavior of three different electrode arrangements for level determination of tanks using methods from electrical capacitance tomography. All schemes have in common that the number of receiver electrode is low in order to keep the installation costs low. The schemes simulated for two different tank systems in order to evaluate the sensitivity against changes in the environment. Further the application of a full tomographic approach is investigated.