| 20100277185 | SOIL MOISTURE SENSOR - A soil moisture probe includes a capacitance-type probe and a detection circuit. The probe includes two spaced electrodes on the same side of a printed circuit board (PCB). The electrodes are placed on an inner layer of a multi-layer PCB and the detection circuit may be placed on an outer layer. The PCB also includes a ground plane. The detection circuit generates a sawtooth or triangular wave which is converted to a DC voltage representative of the moisture content of a soil sample into which the probe is inserted. The unique circuit uses the capacitance of the probe as part of a low-pass filter that distorts an oscillator-generated square wave into a saw-tooth or triangular wave. A resistance component of the low-pass filter is adjustable, allowing tuning of the probe and the circuit as needed. | 11-04-2010 |
