Measuring soil moisture and dielectric permittivity in saline environments: Exploring the limits of Complex Dielectric Through Intersections Technology

The electrical properties of materials, specifically dielectric permittivity (ε) and electrical conductivity (σ), are of interest in a wide variety of applications (e.g. agriculture). For example, in porous media such as soil, ε is strongly correlated with water content, and dielectric sensors are routinely employed to measure soil moisture. Soil moisture sensing technologies have been available in the market for decades, including Time Domain Reflectometry (TDR), Impedance Sensors, Capacitance and Frequency Domain Reflectometers (FDR). These sensors all measure the apparent dielectric permittivity ε_a, which is a function of both the imaginary dielectric permittivity (ε_i) and ε_r. Sensor technology needs to be developed to measure both ε_r and ε_i in order to overcome the impact of salts on water content measurements and take the next technological step forward. A new method, the four-voltmeter method (4VM) is a complex dielectric sensor that determines both the ε_r and ε_i by measuring voltage amplitudes at multiple circuit nodes. The 4VM improves dielectric permittivity measurements under saline conditions by combining multiple independent admittance estimates to account for conductivity-induced errors, avoid loss of sensitivity, and maintain accuracy across a wide range of salinities. The goal of this project is to assess the performance of 4VM in a sandy soil across a range of salinities up to 50 dS/m and assess its true performance.