Accurate measurement of soil moisture content is a crucial prerequisite for achieving agricultural irrigation automation and promoting water-saving technologies. This paper designs a soil moisture detection device based on frequency response characteristics, utilizing the principle that changes in soil dielectric constant with varying moisture content induce changes in plate capacitance, which in turn affect the circuit frequency characteristics. To achieve optimal sensitivity, three types of series loads were investigated. Through scanning analysis in the 10~50 MHz frequency band, the optimal operating frequency was determined to be 34.8 MHz, and the optimal series load resistance was found to be 556 Ω. To address systematic deviations between theoretical and measured values, a proportional coefficient calibration method was proposed, resulting in an average calibration coefficient λ=1.326. Experiments showed that the calibrated theoretical capacitance values fitted well with the measured values, with a determination coefficient R²=0.865, meeting the accuracy requirements for soil moisture detection in agricultural irrigation.

Zhan Qu, Mingquan Wang, Haifeng Pu, Runzhen Zhang, Le An. Research on Frequency Response Characteristics and Parameter Optimization of Soil Moisture Sensors. International Journal of New Developments in Engineering and Society (2026), Vol. 10, Issue 1: 32-38. https://doi.org/10.25236/IJNDES.2026.100105.

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