Design, Fabrication and Testing of Fringing Electric Field Soil Moisture Sensor for Wireless Precision Agriculture Applications

In this study, a fringing electric field (FEF)-capacitance based wireless soil moisture sensor has been designed, fabricated and tested to measure the volumetric water content (VWC) of soil for application in precision agriculture. Typically, the performance of the sensor is evaluated based on parameters such as penetration depth, signal strength, sensitivity and linear response. This paper presents the simulation results for the sensitivity analysis of the soil moisture sensor due to the effects of the electrode size and number of ground electrode. Simulations are conducted using finite element analysis (FEA) software, Finite Element Method Magnetics® (FEMM). From the simulation results, selected design of the FEF soil moisture sensors have been fabricated using printed circuit board technology. During testing, the measured capacitance from the sensor is connected directly to the device input using capacitance to digital converter. Data obtained from the sensor will be transferred wirelessly to the Zigbee coordinator; which is connected to the data base; using sensor mote. Testing revealed that the sensor is capable of detecting moisture from 1% to 80% VWC with a linear response. Test results obtained are then compared with FEMM simulations and benchmark sensor for validation purpose.