Calibration and validation of an embedded AD5933 impedimetric sensor system for soil organic carbon measurement

This article presents the development and validation of an embedded sensor system for the measurement of soil organic carbon (SOC) using the AD5933 impedance analyzer integrated with an Arduino microcontroller. The system includes a DS1077 programmable clock and custom shields for real-time field deployment. Calibration was performed using known resistors to derive gain and phase correction parameters essential for accurate resistance-based SOC estimation. Distinct predictive models were formulated for soils with low (≤4%) and high (>4%) carbon concentration to improve precision across various soil types. In low-carbon soils, the system demonstrated strong predictive performance (R2 = 0.97), while the overall model maintained high accuracy (R2 = 0.92) across a 0%-8% SOC range. Compared to a conventional lab-based impedance analyzer (HIOKI IM3536), the proposed system offers comparable accuracy, enhanced portability, and reduced cost. This work highlights the system's potential for precision agriculture through scalable, real-time SOC monitoring.

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