Soil water and conductivity sensing system
AssigneeThe United States of America as represented by the Secretary of Agriculture
InventorsSteven R. Evett, Scott K. Anderson, Joaquin J. Casanova, Robert C. Schwartz
Life of this patent
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Abstract
Soil water content and bulk electrical conductivity may be determined by time domain reflectometry at multiple depths in the soil such that the entire soil profile from the surface to a user-selected depth may be characterized. A short rise-time pulse is passed into an electrode and the reflected pulse is captured at multiple times. A waveform of reflection coefficient versus time is determined, which may be used to determine the pulse travel time, effective frequency and reflection coefficients at times necessary for the determination of the soil water content and bulk electrical conductivity.
Claims13
An apparatus for determining soil water content and bulk electrical conductivity, the apparatus comprising a time domain-based device, either time domain reflectometry (TDR) or time domain transmission (TDT), the apparatus comprising:
- a) a hollow, substantially cylindrical tube comprising an exterior and interior surface with upper and lower ends, said tube constructed at least in part from a non-conductive material;
- b) at least two electrodes mounted longitudinally onto said exterior surface of said tube, one of said electrodes adapted to transmit an electronic pulse therethrough and designated a voltage electrode, and the other electrode(s) comprising ground electrodes, the electrodes being in communication with a TDR or TDT circuit;
- c) an electronic pulse generator in communication with said voltage electrode effective for transmitting an electronic pulse therethrough;
- d) a voltage receiver in communication with said voltage electrode effective for receiving a reflected pulse therefrom.
A method for determining the water content and bulk electrical conductivity of soil comprising:
- a) providing a time domain reflectometry or time domain transmission sensor comprising:
- 1) a hollow, substantially cylindrical tube comprising an exterior and interior surface with upper and lower ends, said tube constructed at least in part from a non-conductive material;
- 2) at least two electrodes mounted longitudinally onto said exterior surface of said tube, one of said electrodes adapted to transmit an electronic pulse therethrough and designated a voltage electrode, and the other electrodes comprising ground electrodes;
- 3) an electronic pulse generator in communication with said voltage electrode effective for transmitting an electronic pulse therethrough;
- and
- 4) a voltage receiver in communication with said voltage electrode effective for receiving a reflected or transmitted pulse therefrom;
- b) embedding said sensor in said soil with said electrodes in contact therewith;
- c) transmitting an electronic pulse from said electronic pulse generator through said voltage electrode;
- d) receiving a reflected or transmitted pulse from said voltage electrode by said voltage receiver;
- e) calculating the reflection coefficient for multiple times such that a waveform of reflection or transmission coefficient values versus travel time is constructed;
- f) determining the pulse travel time through said voltage electrode by analyzing the waveform;
- g) determining the effective frequency of the pulse;
- h) determining the soil bulk permittivity from the effective permittivity;
- i) determining the bulk electrical conductivity;
- j) calculating the soil water content from the travel time, bulk electrical conductivity, temperature and effective frequency.
Dependencies are inferred from the claim text.