Electrical sensor for determining the moisture content of soil

A moisture sensor for insertion into a moisture containing media to determine the amount of said moisture by measuring the capacitance and resistance of said media comprising:

• a base for maintaining in alignment probe means which extend outwardly from said base including a plurality of elongated conductors disposed around a centrally disposed elongated conductor to form an effective coaxial capacitor defining adjacent extending surfaces partially bounding at least one volume containing said media when said moisture sensor is inserted in said media;
• and circuit means connected to said probe means extending outwardly for applying an ac signal thereto to measure the electrical impedance between said bounding surfaces and thereby determine the moisture content and salinity of said media;
• said circuit means comprising:
• oscillator means for applying electric stimulus to a pair of resistors connected in series to probe means for registering impedance of the material into which said probe means is placed;
• and separate voltage measuring means, M.sub.1, M.sub.2 and M.sub.3, placed respectively between said oscillator means and the first of said resistors between said resistors and between said probe means and the second of said resistors;
• said electrical impedance being characterized by the capacitance and resistance of said material, which capacitance and resistance is a function of the voltage, V.sub.1, V.sub.2 and V.sub.3 measured respectively by said voltage measuring means M.sub.1, M.sub.2, and M.sub.3 and the frequency of said electric stimulus and permitting calculation of said amount of moisture.