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A moisture sensing device for an irrigation system. A pair of concentrically disposed cylindrical conductors are separated by a layer of beads, such that a capacitor is formed whose resistance will vary in response to the level of moisture present in the fibrous material. An electrical circuit is co

A moisture sensing device for an irrigation system. A pair of concentrically disposed cylindrical conductors are separated by a layer of beads, such that a capacitor is formed whose resistance will vary in response to the level of moisture present in the fibrous material. An electrical circuit is connected across the cylindrical conductors for measuring the variable resistance caused by the level of moisture present in the layer of beads. If the soil is dry enough to require watering, the sensor circuit will produce an output signal to the appropriate solenoid in the irrigation system to permit watering.

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A moisture sensing device, comprising: a sensor having a pair of concentrically disposed conductors, each said conductor being in the form of a hollow cylinder, and both said conductors being contained in a generally cylindrical enclosure having screen means for permitting moisture to ingress and eg

A moisture sensing device, comprising: a sensor having a pair of concentrically disposed conductors, each said conductor being in the form of a hollow cylinder, and both said conductors being contained in a generally cylindrical enclosure having screen means for permitting moisture to ingress and egress through said sensor, said conductors being separated by a porous layer of dielectric bead-like material to form a capacitor whose resistance will vary in response to the level of moisture present in said dielectric bead material, a porous layer of said bead-like material also being interposed between the outer one of said conductors and said enclosure, said outer conductor being constructed of an electrically conductive, tubular formed mesh material and having a different length than the inner one of said conductors; and circuit means connected across said conductors for measuring the variable resistance caused by the level of moisture present in said dielectric bead material.