The soil moisture sensor based on soil dielectric property

As we know, soil dielectric property varies along with soil volumetric water content variation. In this paper, the high-frequency resonance measurements method is used to design the soil moisture sensor. Firstly, the high-frequency equivalent electronic model is built by soil and sensor circuit. The relationship between the soil volumetric water content and resonant frequency is established by means of the high-frequency equivalent electronic model analysis. Then, with the comparison test on red soil, moisture soil and paddy soil, the high-frequency resonance measurements method is proved to be effective in soil moisture detection. Finally, the influence of resonant frequency and ambient temperature on the relationship is analyzed. The calibration method of soil moisture sensor is given. The ideally measuring result of soil volumetric water content is obtained. To the best of our knowledge, this paper is the first study on soil moisture sensor design based on soil dielectric property, which covers circuit theory, hardware simulation, resonance frequency selection and temperature compensation. The hardware circuit which is used in soil moisture sensor has advantages of simple structure, efficient practicability. The experiment results show that the soil moisture sensor works well and suits for building large-scale agriculture wireless sensor networks.