Wireless Soil Moisture Sensor Based on Fringing Capacitance
Darold C. Wobschall, D. Lakshmanan · 2006
A soil moisture sensor was developed which was based on fringing capacitance and the increase in dielectric constant of a soil-water mixture with water content. The frequency shift of an RC oscillator connected to the capacitance sensor electrode was measured by a microcontroller. The data, in IEEE 1451 format, is communicated by a built-in RF transmitter (433MHz) to a receiver or base station for logging and display. This battery-operated sensor/transmitter is expected to have an operational life of several years.