Medium-frequency electromagnetic device to measure electric conductivity and dielectric permittivity of soils

International audienceAn electromagnetic (EM) tool working in the medium-frequency range allows the determination of the electric conductivity and dielectric permittivity of soils with a single measurement. It brings information about different state parameters of soils, especially their water and clay contents for a significant volume of investigation. To investigate these properties, a medium-frequency-range EM prototype, the CE120, was built using a perpendicular coil Slingram configuration with a working frequency of 1.56 MHz and a fixed coil spacing of 1.2 m. This configuration was chosen using modeling with the purpose of measuring electric resistivities up to a few thousands of ohm-meters and relative dielectric permittivities as low as two. These thresholds match the expected parameters values in the medium frequency range. Moreover, the CE120 characteristics allowed for an investigation depth between 2 and 2.5 m, depending on the nature of the soil. The prototype was tested on two different soils with water variations: sandy alluvia and clay-loam soil