Research and Design of Soil Water Content Sensor Based on High-frequency Capacitive

Power supply and long distance cable are difficult in a field. Hence, a low power high-frequency capacitive soil water content sensor was developed. It consisted of an adjustable signal generating circuit, a signal attenuator, a true RMS detection circuit, a RC charge and discharge circuit, and two probe electrodes. The probe electrode was made up of PCB (Printed Circuit Board). In order to reduce entire energy consumption, the optimization design of sensor circuit was conducted. The results showed that the output voltage of the sensor had a positive linear correlation with soil volumetric moisture content, and the coefficient of determination R2 was 0.989. The stability and consistency of the soil moisture sensor met the needs of the long-term monitoring soil moisture content. Copyright © 2014 IFSA Publishing, S. L.