基于频率响应特性的土壤墒情检测研究

Research on soil moisture detection based on frequency response characteristics

土壤墒情的测量是实施节水灌溉的基础,是实现农业灌溉自动化的关键环节。本文设计了一种基于频率响应特性的土壤墒情检测装置,当土壤墒情发生变化时,内部介电常数也会发生变化,导致极板电容值发生变化,最终使得电路的频率特性发生变化。为了使极板对频率特性变化的反应最灵敏,设计了3种不同的串联负载,通过多频段内分析频率特性函数,得到了最优的工作频率35 MHz和555Ω的负载阻值。提出了理论值乘比例系数的标定方法,测试结果表明:传感器标定后的理论值与试验值拟合良好,决定系数R^(2)=0.877,满足农业灌溉对土壤水分检测的要求。

Soil moisture measurement is the basis of implementing water-saving irrigation,and the key to realize agricultural irrigation automation.A soil moisture detection device based on frequency response characteristics is designed.When soil moisture changes,the internal dielectric constant will also change,resulting in the change of plate capacitance,finally,results in the change of frequency characteristics of the circuit.In order to make response of plate to the change of frequency characteristics the most sensitive,three different series loads are designed.By analyzing the frequency characteristic function in multiple frequency bands,the optimal load resistance values at the optimal working frequency of 35 MHz and 555Ωare obtained.The calibration method of the theoretical value multiplied by the proportional coefficient is proposed.The test results show that the theoretical value of the sensor after calibration fits well with the experimental value,and the determination coefficient R^(2)=0.877,which meets the requirement of soil moisture detection for agricultural irrigation.