CAPACITANCE SENSOR FOR SOIL MOISTURE MEASUREMENT.

This study was undertaken to develop new instrumentation that could be permanently installed in highway substructures for long-term monitoring of moisture content. A concept that involved the relationship between the amount of water in soil and the dielectric constant, was investigated. The sensor electrodes and soil were incorporated in the resonance circuit whose frequency of oscillation is a function of the circuit components. The circuit design was tested with the electrodes forming a container into which soil could be placed. Several configurations of the embedded sensor were designed and tested.