基于电流-电压四端法的无线土壤电导率传感器研究

On Wireless Soil Electrical Conductivity Sensor Based on Current Voltage Four Terminal Methods

土壤电导率高低包含土壤物理化学性质的丰富信息.为实现土壤电导率的实时自动检测与无线传输,设计利用电流-电压四端法对土壤电导率实时监测,利用Zigbee技术构建无线传感网络实现数据实时传输,利用太阳能电池收集太阳能并存储于锂电池中,实现对系统供电.实验结果表明,当土壤含水率大于15%时,土壤电导率与传感器输出电压呈良好的指数函数关系,系统测量误差小,性能稳定.利用Zigbee模块及MiWi（TM）协议栈构建的星形网络实现数据无线传输,在无阻挡条件下数据可靠传输距离为90m,有阻挡条件下可靠传输距离为50m.在正常天气条件下,系统能自动持续工作,在连续阴雨天气条件下,系统能正常工作10~15d.

The level of soil electrical conductivity contains rich information of soil physical and chemical properties.For automatic detection and wireless transmission soil electrical conductivity,it needs design current voltage four terminal methods on real-time detection of soil electrical conductivity,and use Zigbee technology to realize the data transfer of wireless sensor networks.Solar cells is used to collect solar energy and to be stored in the lithium battery,the realization of the system power supply.The experimental results show that,when the soil moisture content is greater than 15%,the soil electrical conductivity is exponential function relationship with the output voltage of the sensor,the measuring error of the system is small and stable.With the Zigbee module and MiWi（TM）protocol stack constructing star network can realize the wireless transmission of data,the reliable transmission distance under the condition of no barrier for 90m.Under normal weather conditions,the system can automatically work.In the condition of continuous overcast and rainy weather,the system can work well in 10~18d.