Design and Characterization Methodology of Capacitive Sensors for Soil Moisture Sensing Applications

The complete design flow and test procedure for a high-frequency capacitive sensor is presented in this paper. A lowcost fringe field coplanar capacitor is designed and simulated in a High Frequency Structure Simulator (HFSS) and fabricated on a planar printed circuit board. The measurement results show the sensor can operate in the range of 50 MHz to 2 GHz and offers an average sensitivity of 1.55 pF/Gravimetric Water Content (%). The test procedure for sensor testing and sample preparation with standard media is demonstrated.