参数调制探针式电容土壤水分传感技术研究

Technique Considerations on the Use of a Probe Capacitance Sensor with Parameter Modulation for Measuring Soil Moisture Content

电容传感器是实现土壤水分低成本检测的主要途径,土壤水分中电导对土壤水分影响很大,为了消除电导影响,研究了一种新颖的基于参数调制的探针电容土壤水分传感器,分析了参数调制技术消除电导机理,并建立了相应数学模型,设计了参数调制式探针电容土壤水分传感器的检测电路和数据处理系统,通过参数优化得到了一种能够实现在线测试土壤水分的探针电容传感器及检测仪器.试验表明,随着土壤含水量的变化,其探针电容传感器响应有较大的变化,且在低于25%的含水量范围,土壤含水量与被测电压之间呈线性关系.

A capacitance sensor may be the main pathway for low-cost measuring soil water content. Soil conductance has a dramatic change on analyzing soil water content. A novel probe capacitance sensor based on parameter modulation for sensing soil sample water content is introduced in order to eliminating the conductance influence. The mechanism of parameters modulation is analyzed and the mathematic model is established. A kind of modulating circuit and data acquisition system are designed for these applications. A sensor and a device for measuring the soil water content in field are fabricated after optimizing some parameters Experimental data demonstrates good sensitivity to parameter variation, and a nearly linear dependency is observed between soil water content and the measured sample voltage when the soil water content is below 25 %.