Modular Impedimetric Sensing Platform for Laboratory and Field Characterization in Precision Agriculture

Precision horticulture demands affordable and versatile platforms to test a variety of sensors. However, current solutions are often costly, complex, and limited in scope, hindering widespread adoption. Here, we present a modular and practical sensor system designed for the integration and evaluation of printed impedimetric sensors. The platform includes an impedance analyzer, two 16-channel multiplexers, and a Raspberry Pi. Using the developed data acquisition system, we fully characterized the electrical impedance spectroscopy response of an ammonia gas sensor and three humidity sensors over a frequency range from 500 Hz to 10 MHz. The chemiresistive ammonia sensor, tested in a controlled laboratory environment using a gas exposure setup, showed optimal operation at 4 kHz, demonstrating high sensitivity in impedance magnitude measurements. In contrast, the paper-based humidity sensors were evaluated directly on plants under field conditions, where analysis of phase angle (Θ) and impedance magnitude (Ω) identified optimal measurement points. At lower frequencies (below10⁴Hz), both parameters showed strong correlations with relative humidity, with correlation coefficients of0.52 ± 0.03and-0.54 ± 0.02, respectively. These results indicate a capacitive response to moisture absorption and good reproducibility between devices. Beyond10⁵Hz, the correlation weakened, indicating a transition in sensor response mechanisms. Our results demonstrate the effectiveness of the platform in both laboratory and field environments, providing a robust and cost-effective tool to evaluate impedimetric sensors. By enabling rapid and accurate assessments, this system advances agricultural technology for more efficient, sustainable precision horticulture.