Non-invasive measurement of moisture distribution using TDR

Abstract

‘Time domain reflectometry imaging’ (TDRI) is a new technique for non-invasive measurement of moisture content distribution. A series of TDR measurements taken from one side of the material are inverted using a previously described forward model and iterative improvement of an initial estimated moisture distribution. An adapted conjugate gradient optimisation method that avoids time consuming line searches and employs an electric field surrogate for the Jacobian has provided rapid iteration. Then, coupled with a new blocking technique to accelerate the convergence of buried cells and depending on the initial distribution, between 20 and 100 forward calculations are required to solve a 2-D, 6 by 3 element model.