Patent ID: 7482820

Claim:
A device for determining a moisture content value and a salinity value of a soil, the device comprising: a probe conducting structure to be placed in the soil to form a capacitor; a soil moisture circuit comprising a high frequency oscillator for applying a first electrical stimulus to the probe structure, a reference capacitor connected in series to the high frequency oscillator, and a first voltage meter located between the high frequency oscillator and the reference capacitor; a soil salinity circuit comprising a low frequency oscillator for applying second electrical stimulus to the probe structure, a reference resistor connected in series to the low frequency oscillator, and a second voltage meter located between the low frequency oscillator and the reference resistor, wherein the low frequency oscillator is substantially lower in frequency than the high frequency oscillator; a third voltage meter; and a processor, the processor calculating a capacitance of the soil as a function of (V 3 ″−V 3 )/(V 1 ′−V 1 ) to obtain a soil moisture content value wherein V 1 is the output voltage measured by the first voltage meter when the low frequency oscillator and the high frequency oscillator are inactive, V 3 is the output voltage measured by the third voltage meter when the low frequency oscillator and the high frequency oscillator are inactive, V 1 ′ is the output voltage measured by the first voltage meter when the low frequency oscillator is inactive and the high frequency oscillator is active, and V 3 ″ is the output voltage measured by the third voltage meter when the low frequency oscillator is inactive and the high frequency oscillator is active, and the processor calculating a resistance of the soil as a function of (V 3 ′−V 3 )/V 2 ′−V 2 ) to obtain a soil salinity value wherein V 2 is the output voltage measured by the second voltage meter when the low frequency oscillator and the high frequency oscillator are inactive, V 2 ′ is the output voltage measured by the second voltage meter when the low frequency oscillator is active and the high frequency oscillator is inactive, and V 3 ′ is the output voltage measured by the third voltage meter when the low frequency oscillator is active and the high frequency oscillator is inactive.