An Accurate Measurement Sensor for Volumetric Soil Water Content

Self-calibrating, low-cost, microprocessor based, combined soil volumetric water content, conductivity, and temperature sensor is proposed herein. The objective of this feasiblity study is to conduct tests to evaluate the device under a variety of conditions and to demonstrate the validity and viability of the sensor design. Existing low-cost, high volume commercial devices designed to determine soil moisture by measuring electrical properties (conductance or capacitance) of an admixture of soil, water, salts, fertilizers, etc. have not been able to adequately resolve, utilize and/or interpret the components of reactive impedance (conductance/resistance and impedance) to provide an accurate, and repeatable measurements, especially measurements of soil moisture under a broad range of field conditions. As a result, low cost, currently available sensors may operate under limited or idealized conditions, but do not function properly under a range of typical real world conditions. An improved electronic design overcomes the short comings of earlier sensor designs providing a true, accurae measurement of capacitive reactance due to water in soil under a wide range of conditions. In addition, other significant factors effecting the soil water content determination, including temperature, conductivity, and in-situ calibration, are addressed and solved in this innovative design.