Based on the measurement principle of capacitively coupled contactless conductivity detection, a new dual-modality electrical capacitance tomography (ECT)/electrical resistance tomography (ERT) technique is proposed, and hence, a new integrated dual-modality ECT/ERT system is developed. First, with the digital phase-sensitive demodulation technique, the capacitance and resistance measurements of the fluid are obtained simultaneously. Then, a modality recognition method, which is on the basis of the    $k$   -nearest neighbor algorithm, is proposed to automatically implement the modality switching between two different modalities (ECT modality and ERT modality). Finally, with the modality recognition result, ECT or ERT modality is selected to reconstruct the cross-sectional image of the permittivity or the conductivity distribution of the fluid. Static experiments and dynamic experiments were carried out. Experimental results demonstrate the feasibility of the proposed dual-modality ECT/ERT technique and the effectiveness of the developed dual-modality ECT/ERT system. The research results also indicate that the proposed modality recognition method is effective and can determine the correct modality. The qualities of the reconstructed images in ECT modality or ERT modality are satisfactory.
['Haifeng Ji', 'Wuhao Tan', 'Zhongbao Gui', 'Baoliang Wang', 'Zhiyao Huang', 'Haiqing Li', 'Guohua Wu']
A New Dual-Modality ECT/ERT Technique Based on C 4 D Principle