Contributions to the measured capacitance by the dielectric properties of water in insulated electrode soil moisture sensors

In a soil/water matrix, water has a much higher dielectric constant than that of the other soil components. Capacitance measurement methods are often used to measure the soil water content. Many capacitance soil moisture sensors employ a probe consisting of two electrodes of which one or both are insulated from the matrix. The capacitance between the probes varies as a junction of water content. Theoretical analysis of a sensor arrangement employing two electrodes with an insulating coating is performed and compared to experimentally derived data. Both show that conduction effects within the matrix mask the contribution to the measured capacitance by the dielectric properties of water.