Soil moisture sensor with data transmitter

• US 20090302870A1
• Filed: 09/12/2007
• Published: 12/10/2009
• Est. Priority Date: 09/12/2006
• Status: Abandoned Application

• Current Assignee: Aquaspy Group Pty., Ltd. (Aquaspy, Inc.)
• Original Assignee: Aquaspy Group Pty., Ltd. (Aquaspy, Inc.)
• Inventors: Paterson, Neil D., Cave, Richard J., Wilson, Neil M.
• Application Number:
  US12/310,946
• Publication Number:
  US 20090302870A1
• Time in Patent Office: Days
• US Class Current: 324/670
• CPC Class Codes: A01G 25/167 Control by humidity of the soil itself or of devices simulating soil or of the atmosphere; Soil humidity sensors
• CPC Class Codes: G01N 27/223 for determining moisture content, e.g. humidity rain detectors on vehicle windows B60S1/0825
• CPC Class Codes: G01N 33/24 Earth materials G01N33/42 takes precedence
• CPC Class Codes: Y02A 40/22 Improving land use; Improving water use or availability; Controlling erosion

Abstract

A sensor and method for sensing moisture content of a medium such as soil is disclosed. In an embodiment, the sensor includes a sensing circuit, a processing module, a register, and a communications interface for communicatively coupling the sensor to an external communications device. In use, the sensing circuit generates a sensed signal having a signal parameter value attributable to the moisture content of the medium. The processing module processes the signal parameter value to provide, at an output, a scaled data value. The register stores a sensor identifier for the sensor and the communications interface is capable of communicating the scaled data value and the sensor identifier to the external device. An irrigation control system is also disclosed.

Claims

1. A sensor for sensing moisture content of a medium such as soil, the sensor including:

a sensing circuit for generating a sensed signal having a signal parameter value attributable to the moisture content of the medium;

a processing module for processing the signal parameter value to provide, at an output, a scaled data value;

a register for storing a sensor identifier for the sensor; and

a communications interface for communicatively coupling the sensor to an external communications device to communicate the scaled data value and the sensor identifier thereto.

2. A sensor according to claim 1 wherein the communications interface includes a bi-directional communications interface and wherein the processing of the signal parameter value is configurable via the bi-directional communications port.

3. A sensor according to claim 2 wherein the sensing circuit includes an oscillator, the oscillator including a paired electrode arrangement forming a capacitive element having a value of capacitive reactance attributable to a dielectric constant of the medium, and wherein the signal parameter value of the sensed signal is a resonant frequency of the oscillator.

4. A sensor according to claim 3 wherein the sensor further includes an integral temperature sensor for sensing the temperature within a sensed zone of the medium and wherein the processing applies a temperature compensation factor according to the sensed temperature so that the scaled data value is temperature compensated.

5. A sensor according to claim 2 wherein the bi-directional communications interface is configured to communicate packet based data.

6. A sensor according to claim 1 wherein the sensing circuit includes an oscillator configured such that when the sensor is inserted into a soil medium the oscillator generates a sensed signal having a frequency signal parameter value (f_osc) that varies according to the dielectric constant of the medium.

7. A sensor according to claim 6 wherein the oscillator includes a pair of sensing elements coupled in parallel with a series LC arrangement represented as a bulk capacitance and a bulk inductance, and wherein the bulk capacitance and the bulk inductance form a resonant circuit having a resonant frequency f_osc.

8. A sensor according to claim 7 wherein the pair of sensing elements includes either a pair of co-planar planar conductive electrodes or a pair of co-axially arranged cylindrical conductive electrodes.

9. A sensor according to claim 8 wherein the pair of co-planar planar conductive electrodes comprise a pair of strip lines and wherein a series capacitance is connected to one of the electrodes so that sensor'"'"'s strip line inductor appears capacitive (non-resonant) across the range operating frequency range of the oscillator.

10. A sensor according to claim 9 wherein the ratio between the series capacitance and a series combination of the capacitance of the series capacitance and conductive electrode is selected to resonate the bulk inductance at a frequency in the range of substantially 127.79 MHz to 163.84 MHz (F_α

) in air, and at a frequency in the range of substantially 93.38 MHz to 114.6 MHz (F_W) when the sensor is fully submerged in water.

11. A sensor according to claim 10 wherein the scaled data value S_F is a dimensionless number in the range 0 to 1 which is given by

$S_F=\frac{\left(F_a-F_s\right)}{\left(F_a-F_W\right)}$

where:

F_S is the frequency of oscillation in the medium (soil count).

12. A sensor according to claim 1 wherein the sensing circuit includes an oscillator configured such that when the sensor is inserted into a soil medium the oscillator generates the sensed signal, the sensed signal having a frequency signal parameter value (f_osc) that varies according to a dielectric constant of the soil medium, and wherein the processing module processes, over a predetermined gate time, the sensed signal to derive a count value (F_S) indicative of the number of counts of the sensed signal detected during the gate time, and wherein providing the scaled data value includes processing the count value (F_S), and frequency values indicative of in air (F_α

) and in water (F_W) frequencies respectively.

13. A sensor according to claim 12 wherein the scaled data value S_F is a dimensionless number in the range 0 to 1 which is given by

$S_F=\frac{\left(F_a-F_s\right)}{\left(F_a-F_W\right)}$

where:

F_S is the frequency of oscillation in the soil medium (soil count).

14. A sensor for sensing moisture content of a medium such as soil, the sensor including:

a sensing circuit for generating a sensed signal having a signal parameter value attributable to the moisture content of the medium, the sensing circuit including an oscillator configured such that when the sensor is inserted into the medium the oscillator generates the sensed signal, the sensed signal having a frequency signal parameter value (f_osc) that varies according to a dielectric constant of the medium;

a processing module for processing the signal parameter value to provide, at an output, a scaled data value (S_F), the processing including deriving a count value (F_S) of the sensed signal (f_osc) detected during a gate time, and processing the count value (F_S), and frequency values indicative of in air (F_α

) and in water (F_W) frequency values respectively to calculate the scaled data value S_F wherein;

$S_F=\frac{\left(F_a-F_s\right)}{\left(F_a-F_W\right)};<br><br>$

a register for storing a sensor identifier for the sensor; and

a communications interface for communicatively coupling the sensor to an external communications device to communicate the scaled data value and the sensor identifier thereto.

15. A sensor according to claim 14 wherein the frequency values (F_α

) and (F_W) are stored in memory on board the sensor.

16. A computer readable medium containing a computer software program for programming a sensor for sensing moisture content of a soil medium, the software program being executable by a processor module to cause the sensor to:

generate a sensed signal having a signal parameter value attributable to the moisture content of the medium;

process the signal parameter value to provide, at an output, a scaled data value;

access a register to retrieve a sensor identifier for the sensor; and

activate a communications interface communicatively coupling the sensor to an external communications device to communicate the scaled data value and the sensor identifier thereto.

17. A computer readable medium according to claim 16 wherein the step to process the signal parameter value includes deriving a count value (F_S) of the sensed signal (f_osc) detected during a gate time, and processing the count value (F_S), and frequency values indicative of in air (F_α

) and in water (F_W) frequency values respectively to calculate the scaled data value S_F wherein;

$S_F=\frac{\left(F_a-F_s\right)}{\left(F_a-F_W\right)}.$

18. A computer readable medium according to claim 17 wherein the step to process the signal parameter value further includes applying a temperature compensation factor according to a sensed temperature value obtained from a temperature sensor for sensing temperature within a sensed zone of the soil medium.

19. A method of obtaining a measurement value from a sensor for sensing moisture content of a medium such as soil, the method including:

inserting the sensor into the medium having a moisture content;

the sensor generating a sensed signal having a signal parameter value attributable to the moisture content of the medium;

controlling a processing module associated with the sensor to;

process the signal parameter value to provide, at an output of the sensor, a scaled data value;

access a register to retrieve a sensor identifier for the sensor; and

activate a communications interface communicatively coupling the sensor to an external communications device to communicate the scaled data value and the sensor identifier thereto.

20. A method according to claim 19 wherein the step to process the signal parameter value includes deriving a count value (F_S) of the sensed signal (f_osc) detected during a gate time, and processing the count value (F_S), and frequency values indicative of in air (F_α

) and in water (F_W) frequency values respectively to calculate the scaled data value S_F wherein;

$S_F=\frac{\left(F_a-F_s\right)}{\left(F_a-F_W\right)}.$

21. A method according to claim 20 wherein processing the signal parameter value further includes applying a temperature compensation factor according to a sensed temperature value obtained from a temperature sensor for sensing temperature within a sensed zone of the medium.

22. An irrigation control system for controllably interrupting a programmed irrigation cycle, the irrigation control system including:

a sensor including;

a sensing circuit for generating a sensed signal having a signal parameter value attributable to moisture content of a medium such as soil;

a processing module for processing the signal parameter value to provide, at an output, a scaled data value;

a register for storing a sensor identifier for the sensor; and

a communications interface for communicatively coupling the sensor to an external communications device to communicate the scaled data value and the sensor identifier thereto; and

an external communications device including;

a user-settable input for entering a high-set point level value; and

a comparator for comparing the scaled data value with the high-set point value to provide, responsive to the comparison, a control signal for actuating a switching means to interrupt the programmed irrigation cycle.

23. (canceled)

24. (canceled)