Research on soil moisture detection based on frequency response characteristics
Soil moisture measurement is the basis of implementing water-saving irrigation,and the key to realize agricultural irrigation automation.A soil moisture detection device based on frequency response characteristics is designed.When soil moisture changes,the internal dielectric constant will also change,resulting in the change of plate capacitance,finally,results in the change of frequency characteristics of the circuit.In order to make response of plate to the change of frequency characteristics the most sensitive,three different series loads are designed.By analyzing the frequency characteristic function in multiple frequency bands,the optimal load resistance values at the optimal working frequency of 35 MHz and 555Ω are obtained.The calibration method of the theoretical value multiplied by the proportional coefficient is proposed.The test results show that the theoretical value of the sensor after calibration fits well with the experimental value,and the determination coefficient R2=0.877,which meets the requirement of soil moisture detection for agricultural irrigation.
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