OPTIMIZATION AND CALIBRATION OF MOBILE DIELECTRIC PROBE FOR NONDESTRUCTIVE EVALUATION APPLICATION TO TIMBER

摘要

fa this study, three main objectives have been set. The first is to develop an accurate method for measuring the dielectric properties of timber using a mobile dielectric probe (MDP) that has been recently developed for field evaluation of timber. The MDP consists of two conducting plates, connected to a LCR meter, with a specific separation between them. The second is to optimize the MDP design configuration for different timber sample thickness. The third objective is to develop a predictive model that correlates the penetration depth of the electric field in timber with its critical parameters such as plate shape, plate size, separation distance and frequency. Three calibration methods have been developed and evaluated for the MDP to measure the dielectric properties of timber namely; short, open, and known materials. The selected calibration method was used to optimize and validate the MDP fixture for field application by layers of square plywood sheets 300 x 300 mm. The effective penetration depth of the electromagnetic field for different MDP design configuration was optimized by computer simulation. The results have been used to develop a predictive model that correlates the effective penetration depth with the plates' shape, size, separation between them, and the exiting frequency. Thus, an optimum design for different desired penetration depth was achieved.