Research And Implementation Of Soil Moisture Sensor Based On Standing-Wave Ratio Theory

With the development of modern equipment technology and the demand of agricultural big data,accurate and rapid soil moisture detection is the foundation of agricultural modernization.In view of the application of soil moisture data in agricultural intelligent moisture detection,based on the microwave technology and the transmission line theory,the standing wave ratio method is used in this paper,The method of indirectly detecting soil moisture content by detecting standing wave voltage is studied and achieved in this paper.Lack of research on existing methods,this paper,based on the theoretical basis,takes the drying method as the standard,and measured the standing wave voltage when the soil moisture is calibrated under the different probe length structure of the sensor.The curve fitting is carried out according to the scattered point data obtained by the experiment.The optimum probe length is selected according to the fitting error..According to the mathematical model obtained in this paper,the Guizhou loam soil is tested,and compared with the measurement data of others,the purpose of improving the precision of the sensor is achieved through the experiment.The sensor model obtained by Guizhou loam soil is used to measure the Hubei sand soil,and the measurement error is analyzed.It is proved that the soil moisture sensor studied in this paper is common to different types of soil;compared with the commonly used FD soil moisture sensors in the market and analyzed the measurement error,the soil moisture transmission studied in this paper is verified by the actual test.The advantage of sensor in measurement accuracy.By analyzing the influence of ambient temperature on the dielectric constant of the theoretical model of the sensor,the temperature compensation of the sensor was introduced by two dimensional regression analysis method,and the experimental comparison with the soil with different water content was carried out to verify the accuracy of the temperature compensation method used in this paper to improve the precision of the soil moisture sensor at different ambient temperatures.In view of the application of soil moisture sensor in agricultural moisture and intelligent irrigation,combined with the research results of soil moisture sensor based on the standing wave rate method,a soil moisture collection system based on STM32 microcontroller is designed,which embodies the practical significance of this study.