Soil moisture sensor

A moisture sensor device for sensing the moisture content of a volume of a medium, the medium having a dielectric constant dependant on the medium's moisture content, the device comprising:

• an LC oscillator circuit having an inductance element and a capacitance element and an oscillation frequency dependent on the values of the inductance and capacitance elements;
• wherein the capacitance element comprises first and second spaced apart conductive sensor elements configured to be disposed within said volume of the medium, to provide a capacitance dependent upon the dielectric constant of the medium when disposed within said volume of the medium;
• and
• an output circuit for providing a moisture content indicative output signal as a function of the oscillation frequency of the LC oscillator circuit.

A moisture sensor system for sensing the moisture content of a medium, the medium having a dielectric constant dependant on the medium's moisture content, the system comprising:

• at least one moisture sensor device having an LC oscillator circuit provided with an inductance element, a capacitance element and an oscillation frequency dependent on the values of the inductance and capacitance elements, wherein the capacitance element comprises first and second spaced apart conductive sensor elements configured to be disposed within said volume of the medium, to provide a capacitance dependent upon the dielectric constant of the medium when disposed within said volume of the medium;
• an output circuit for providing a moisture content indicative output signal as a function of the oscillation frequency of the LC oscillator circuit;
• and
• a central processing unit for monitoring the output signal of the at least one moisture sensor.

A moisture and conductivity sensor device for sensing the moisture content and conductivity of a volume of a medium, the medium having a dielectric constant dependant on the medium's moisture content and a conductivity dependent on the medium's moisture content and the concentration of conductive material in the medium, the device comprising:

• an LC oscillator circuit having an inductance element and a capacitance element and an oscillation frequency dependent on the values of the inductance and capacitance elements;
• wherein the capacitance element comprises first and second spaced apart conductive sensor elements configured to be disposed within said volume of the medium, to provide a capacitance dependent upon the dielectric constant of the medium when disposed within said volume of the medium;
• a conductivity sensor for sensing the conductivity of the medium with said volume:
• means responsive to the sensed conductivity of the medium within said volume and further responsive to the oscillation frequency of the LC oscillator circuit, for providing a signal representative of the component of the sensed conductivity contributed by the concentration of conductive material in said volume of the medium.