Boundary element modeling of a capacitive probe for in situ soil moisture characterization

There has been a need for accurate numerical modeling of a capacitive probe dedicated to the in situ characterization of soil moisture in measuring the dielectric permittivity of the soil. The objectives of the author´s modeling were to understand the quantitative response of the probe, to optimize the shape of the probe, and to enable accurate calibration. In comparison with other numerical methods (such as the finite element method), the boundary element method appears straightforward and economical. The author presents a generalized version of this method in the case of an axisymmetrical geometry within the quasi-static limit. Numerical results are discussed and compared with the approximation of a lumped circuit