Non‐contact thickness measurement with multilayer radiation structure

Abstract

AbstractMicrowaves have proven their efficiency in the thickness measurement field. However, in certain environments, the full accessibility to the measured samples is one big challenge; an illustration of these challenging environments is the ceramic thickness monitoring in aerospace industry. Since ceramic materials are known for their ability to support high pressure and high temperature, the control of their geometries and structures is of an utmost stature. In literature, several methods have been proposed to allow a non‐contact thickness measurement. One of the well‐known methods is based on waveguide open‐end radiation. Given the need of new accurate structures, a new model that takes into account the air gap between the sensor and the material under test is proposed. Accordingly, the study of multilayered dielectric composite is unavoidable. In this paper, a new multilayer thickness measurement structure using a coaxial waveguide probe is proposed. Moreover, an artificial neural networks algorithm which estimates and corrects the reflection coefficient shift caused by the air gap effect is implemented. Experimental results show that the estimation error of the system is less than 3% for Plexiglas and less than 2% for FR4. More results, with calibration techniques, validate the proposed measurement system.