Fringing Field Sensor Using a Circuit-Modulated Parameter for Measuring Water Content in a Soil Sample

Abstract

Currently used dielectric spectroscopy methods for measuring soil water contents are highly susceptible to their electrical conductivities. Some of the existing methods are double-plate capacitance sensors. A novel technique based on the use of fringing field sensors for the content detection is presented in our work, which is able to perform real-time capacitance measurements, and process recorded data to obtain the given parameters of interest. A modulated circuit and data acquisition system are designed to meet practical application requirements, and high sensitivity of the proposed sensor to parameter variation was demonstrated based on the experimental data. An approximately linear dependency is observed between water content and measurement voltage when the proportion of water content in the soil sample is below 24% (gravimetric water content), which implies a wide-ranging application of such a technique for real-time measurements of various soil water content under field working conditions where conventional instruments are unavailable.