| 摘要 |
This invention is concerned with a method and apparatus to measure soil water content. A sensor electrode assembly comprised of a sensor electrode fixed to a spherical shape is implanted in undisturbed soil at the bottom of a low narrow hole in the soil under evaluation. A second electrode is implanted in adjacent soil. Water is adsorbed on the surface of the sensor electrode in proportion to the water in the soil. Electrical charge layers are present at the sensor electrode/water interface due to dissolved oxygen in the adsorbed water. These charge layers result in an interfacial capacitance whose magnitude varies with the amount of water in the soil. Under the assumption that the capacitance of the second electrode/adjacent soil interface is constant, the change in capacitance across the two wires connected to the two electrodes give a measure of the change in soil water content. Energy flow during this measurement is unidirectional, that is, from the interfacial capacitance to the measuring device.
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