Development of Indigenous Soil Moisture Sensor Compatible with Data Longger

Most commercially available soil moisture monitoring devices like neutron probe, TDR, FDR, VDD probes, heat dissipation probes, and capacitance probes are imported and so are expensive. Therefore, indigenous parallel plate capacitance based sensors were designed and developed. Four different design capacitances were studied and analyzed for monitoring soil water in vertisols. The geometrical capacitances of these sensors were 0.024nF(=0.024 X 10⁻⁹ F), 0.052nF, 0.76 nF and 0.126nF, respectively. The sensors were evaluated at varying soil moisture regimes to assess the most suitable geometry of sensor. Statistical analysis of data revealed logarithmic relationship between volumetric soil water content and capacitance of all the sensors. Best relationship was observed for a sensor 0.52 nF (R²=0.95). An electronic circuit was designed and developed for display of soil moisture on digital panel meter and to provide corresponding output signal for interfacing the sensor with data logger. The accuracy of measurement was observed as 3% full scale, resolution as 2% of volumetric soil water content, and 0–1 V dc output for continuous monitoring of soil moisture. The electrodes of sensors were made of stainless steel with protective frame of stain less steel to avoid corrosion and provide long-term stability.