Combined Sensor for Capacitive Imaging and Size Measurement for Surface Features

Capacitive imaging (CI) has been successfully used in nondestructive evaluation (NDE) applications. Conventional capacitive electrodes applied to CI technology are generally planar, and only one capacitor type exists in one probe. This work proposes a combined capacitive sensor, which is mainly composed of triangular prism electrodes and auxiliary electrodes, and measurement system for CI technology. Triangular prism electrodes are designed to improve the two-dimensional (2-D) image resolution compared to those of planar electrodes. Two different spatial arrangements of driving and sensing electrodes are applied to achieve the 2-D imaging and depth detection of specimen features. The auxiliary electrode is developed to measure the sizes of surface features and distinguish surface and internal features. Double scans and image superimposition are employed to address image blurring and shape distortion in a single direction of the image due to the different imaging resolutions of probes in two perpendicular directions. The feasibility of the combined sensor in feature imaging and key parameter detection is verified through experiments. This work expands the functionality of conventional capacitive probes by combining different electrodes in one probe and lays a foundation for the subsequent analysis and further processing of CI technology.