基于电容法的非接触式土壤水分传感器设计与性能分析  

Design and Performance Analysis of Soil Moisture Sensor Based on Capacitance Technology

作　　者：高志涛[1,2] 刘卫平[1,2] 赵燕东[1,2] 

机构地区：[1]北京林业大学工学院,北京100083 [2]北京林业大学城乡生态环境北京实验室,北京100083

出　　处：《农业机械学报》2016年第11期185-191,共7页Transactions of the Chinese Society for Agricultural Machinery

基　　金：国家自然科学基金项目(31371537);北京市科技计划项目(Z116100000916012);北京市共建项目专项

摘　　要：针对接触式土壤水分传感器存在对土体破坏大及使用安装、更换困难等问题,设计了一种基于电容法的非接触式土壤水分传感器。借助网络矢量分析仪对传感器环形探头在不同介电常数的有机溶液中进行测量,确定了传感器环形探头电容变化范围为7.08~22.75 p F。选取11种不同电容值高频瓷片分别与102 n H的绕线电感进行并联谐振试验,得到的测试结果与仿真结果的决定系数达到了0.98,检测电路的测量精度能够满足传感器的设计要求。以北京地区粘壤土作为测试样本,对传感器输出与对应的测量值进行了多项式拟合,决定系数达到了0.995 9,系统的稳态与动态性能均能满足土壤水分的检测要求。通过试验分析了温度对传感器输出的影响,将传感器输出结果与温度进行线性拟合,决定系数达到了0.987 9。进一步提出了能量指数Ka,通过试验的方式确定了传感器的纵向影响范围为10 cm,横向影响范围为5 cm。最后对比试验表明,所设计的土壤非接触式水分传感器与国外同类产品性能相当,能够满足土壤非接触式测量的要求,但具有更高的性价比,为同类产品的国产化奠定了基础。A kind of non-contact sensor based on capacitance method was designed. With the aid of the network vector analyzer, the probe of the sensor was measured in the organic solution with different dielectric constants, and the capacitance variation range of the ring probe of the sensor was determined as 7.08 -22.75 pF. This paper formed 11 high-frequency ceramic capacitors with different capacitances respectively connected with 102 nH winding inductor in parallel into resonance circuit. Using the circuit to carry out experiment, the decision coefficient of test results and simulation results all reached 0.98. The measurement accuracy of the detection circuit met the sensor design requirements. Clay loam in Beijing area was chosen as experimental sample. The output of sensor detection unit and the corresponding measured values were carried out the polynomial fitting and linear fitting with a coefficient of determination of 0. 995 9. The static and dynamic performance of the system can meet the soil moisture detection requirements. The effect of temperature on the output of the sensor was analyzed. The output of the sensor was fit with the temperature, and the coefficient was 0. 987 9. The energy index Ko was further proposed. By the experiment, the influence ranges of longitudinal and transverse were identified as 10 cm and 5 cm. Finally, the comparison experiments showed that the proposed non-contact type moisture sensor was similar to that of the foreign products. It met the requirements of non-contact measurement of soil, at the same time, it had high cost-performance and laid the localization foundation for the similar products.

关 键 词：土壤水分传感器 电容法 非接触式 性能分析 

分 类 号：S237[农业科学—农业机械化工程]