FruitMeter: An AD5933-Based Portable Impedance Analyzer for Fruit Quality Characterization

We present a portable impedance analyzer based on the AD5933 integrated circuit for fruit quality monitoring. The system, custom designed, allows a flexible tuning of parameters (i.e. excitation voltage, feedback resistor, settling time) in order to allow a precise system calibration over a frequency range from 10 Hz to 100 kHz. The employment of Low-Energy Bluetooth and USB communication, together with a micro SD data storage and a rechargeable battery, increases the system portability and its connectivity especially for precision and smart agriculture applications. The system (7.5×2×4cm in volume), runs MicroPython on an STM32 microcontroller and provides 300 mAh Li-Po battery storage with USB recharge. The developed system is validated by comparing it with a bench-top impedance analyzer, using two-terminal measurement, for the specific analysis of tomatoes and bananas, showing an average Root Mean Square Error (RMSE) as low as 0.6% and 4.1%, for impedance magnitude and phase, respectively.