US4540936A — Soil moisture sensor

Claim 1

Independent Claim 105 words

A moisture sensor for insertion into a moisture containing media comprising: a base; means extending outwardly from said base including first and second slotted tubes forming an effective coaxial capacitor defining adjacent extending surfaces partially bounding at least one volume containing said media when said sensor is inserted, said bounding surfaces providing an extending opening between said volume and the media therein and the media outside said sensor; and circuit means connected to said means extending outwardly for applying an ac signal thereto to measure the impedance between said surfaces in the region where the opening extends and thereby the moisture content of said media.

Claim 2

Dependent Claim 105 words

A moisture sensor for insertion into a moisture containing media comprising: a base; means extending outwardly from said base including first and second slotted tubes forming an effective coaxial capacitor defining adjacent extending surfaces partially bounding at least one volume containing said media when said sensor is inserted, said bounding surfaces providing an extending opening between said volume and the media therein and the media outside said sensor; and circuit means connected to said means extending outwardly for applying an ac signal thereto to measure the impedance between said surfaces in the region where the opening extends and thereby the moisture content of said media.

Claim 3

Dependent Claim 30 words

A sensor as in claim 1 wherein said means extending outwardly terminates at the end remote from said base in a sharp edge which can be inserted into said media.

Claim 4

Dependent Claim 87 words

A moisture sensor for insertion into a moisture containing media comprising: a base; means extending outwardly from said base for insertion into said media and defining an internal volume with extending openings to the media outside said volume and a capacitance; and circuit means connected to said means extending outwardly for applying an ac signal to said means extending outwardly for measuring the impedance of the media in said volume in the region where the opening extends and thereby the moisture content, including a capacitance dividing circuit.

Claim 5

Dependent Claim 87 words

A moisture sensor for insertion into a moisture containing media comprising: a base; means extending outwardly from said base for insertion into said media and defining an internal volume with extending openings to the media outside said volume and a capacitance; and circuit means connected to said means extending outwardly for applying an ac signal to said means extending outwardly for measuring the impedance of the media in said volume in the region where the opening extends and thereby the moisture content, including a capacitance dividing circuit.

Claim 6

Dependent Claim 106 words

A moisture sensor comprising: a base; a first cylindrical tube extending outwardly from said base and having a plurality of axially extending slots around the periphery thereof; a second cylindrical slotted tube extending outwardly from said base coaxially within said first tube and having a plurality of axially extending slots around the periphery thereof, separated and electrically insulated therefrom, said tubes defining ground planes and forming an effective coaxial capacitor and being insertable into material to be sensed; and circuit means connected to said first and second tubes for applying an ac signal to said tubes for measuring the impedance of said material between said rings.

Claim 7

Dependent Claim 106 words

A moisture sensor comprising: a base; a first cylindrical tube extending outwardly from said base and having a plurality of axially extending slots around the periphery thereof; a second cylindrical slotted tube extending outwardly from said base coaxially within said first tube and having a plurality of axially extending slots around the periphery thereof, separated and electrically insulated therefrom, said tubes defining ground planes and forming an effective coaxial capacitor and being insertable into material to be sensed; and circuit means connected to said first and second tubes for applying an ac signal to said tubes for measuring the impedance of said material between said rings.

Claim 8

Dependent Claim 20 words

A sensor as in claim 4 wherein said base is a plastic plug onto which said tubes are press fitted.

Claim 9

Dependent Claim 23 words

A sensor as in claim 4 wherein one end of each of said tubes remote from said base is sharpened to facilitate insertion.

Claim 10

Dependent Claim 25 words

A sensor as in claim 4 further including an outer cylindrical tube extending coaxially with said first and second tubes for guarding against stray capacitance.

Claim 11

Dependent Claim 17 words

A sensor as in claim 1 or 4 wherein said circuit means includes a capacitance dividing circuit.

Claim 12

Dependent Claim 16 words

A sensor as in claim 1 or 4 wherein said circuit means includes a Wein bridge.

Claim 13

Dependent Claim 105 words

A moisture sensor for insertion into a moisture containing media comprising: a base; a plurality of plates attached to said base and extending outwardly therefrom to define at least one cross-shaped volume with four legs extending outward form a central portion to an open peripheral edge, the end of said plates remote from said base being insertable into said media, said plates defining a plurality of pairs of parallel extending surfaces with each pair defining a capacitor; and circuit means connected to said plates for applying an ac signal thereto to measure the impedance of said capacitors and thereby the moisture content of said media.

Claim 14

Dependent Claim 105 words

A moisture sensor for insertion into a moisture containing media comprising: a base; a plurality of plates attached to said base and extending outwardly therefrom to define at least one cross-shaped volume with four legs extending outward form a central portion to an open peripheral edge, the end of said plates remote from said base being insertable into said media, said plates defining a plurality of pairs of parallel extending surfaces with each pair defining a capacitor; and circuit means connected to said plates for applying an ac signal thereto to measure the impedance of said capacitors and thereby the moisture content of said media.

Claim 15

Dependent Claim 17 words

A sensor as in claim 10 wherein said plates are L-shaped to form a single cross-shaped volume.

Claim 16

Dependent Claim 27 words

A sensor as in claim 10 wherein said plates are L-shaped and U-shaped to form a volume of two crosses connected at the ends of respective legs.

Claim 17

Dependent Claim 14 words

A sensor as in claim 10 wherein said circuit means includes a Wein bridge.

Claim 18

Dependent Claim 15 words

A sensor as in claim 10 wherein said circuit means includes a capacitance dividing circuit.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1988-09-09	1989-03-11	1989-09-10	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1992-09-09	1993-03-11	1993-09-10	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1996-09-09	1997-03-11	1997-09-10	$7700.00	Window Closed / Lapsed

Soil moisture sensor

Abstract

Inventors

Bibliographic Details

Claims Analysis

References Cited (Backward Citations)

USPTO Annuity & Maintenance Windows

Assigned Categories & Tags

Assign Category Tag