Study on soil water content real-time measuring method and sensor structure

The dielectric constant of soil is a key parameter to measure soil water content rapidly and reliably. A measuring method based on impedance commutation of transmission line was presented to measure soil water content in this paper. The sensor measuring performance with different probe structure, i.e. the probe with single pin, 2 pins, 3 pins, and 4 pins, was studied elaborately. 4-pin probe is proved to be the best structure to get linear relationship between voltage and soil water content by experiment results, and it is benefit to collect data, deal with data and export data. The measuring method and the sensor are used in the automatic saving water irrigation system at the Greenbelt demonstration area of Beijing Forestry University, and the results indicate that the measuring method is valid and feasible.