(245a) On the Ect Sensor Based Dual Imaging Modality System for Electrical Permittivity and Conductivity Measurements

Electrical tomography has gained increased attention in industrial process applications due to its low cost, safety, high speed, and suitability for measurements of the flow field in various sizes of vessels. Two major electrical tomography modalities have been the subjects of focused research recently: (1) electrical capacitance tomography (ECT), and (2) electrical impedance tomography (EIT). The former is concerned with the imaging of the permittivity distributions in non-conducting systems, whereas the latter is concerned with that of the conductivity distributions in conductive systems.

Electrical tomography has provided a means for process design, monitoring, and control. In particular, the conductivity/permittivity imaging offers a tool to understand dynamics of multiphase flow systems such as fluidized beds. The use of electrical tomography techniques is challenged by their soft field nature. Nevertheless, the recent research in image reconstruction method has augmented the potential of electrical tomography techniques for industrial applications. In this regard, the 3-D NN-MOIRT reconstruction technique developed by Warsito & Fan (2005) has provided the 3-D imaging capability of the ECT and an improved accuracy in 2-D imaging over that based on other reconstruction techniques commonly employed in the literature.

Recent developments have enabled imaging of the complex impedance (permittivity and conductivity) distributions through direct current injection. This technique requires direct contact between the sensor and the flow field and is restricted to conductive fluids.

In this work, a new non-invasive sensing system capable of imaging permittivity as well as conductivity distributions is introduced. A dual sensitivity matrix is generated for permittivity/conductivity reconstruction. The system is based on using the current amplitude and power dissipation as the interrogating signals. The new system uses the 3-D NN-MOIRT reconstruction technique and the reconstructed results for simulated conditions are obtained and their comparisons are made in this study.