An Improved RF Dielectric Sensor for Real-Time Noninvasive Moisture Measurement of In Situ Corn Kernels

Noninvasive moisture monitoring of corn ears is critical for precision agriculture and mechanized harvesting applications. This article presents an improved RF dielectric sensor using fringe-field differential detection for continuous nondestructive corn ear kernel moisture monitoring. The initial sensor design exhibited a measurement error of 8.2% at the 95% confidence level due to nonuniform axial moisture distribution within kernels and interference from high-moisture corn husks affecting the effective measurement depth of the electrodes. Through systematic optimization of sensor probe structure and measurement circuitry, including expanding the wide electrode (WE) measurement depth coverage from 28% to 57% of the kernel layer and refining the circuit calibration methodology, the measurement error was successfully reduced from 8.2% to 4.2% at the 95% confidence level. Field validation conducted on five in situ corn ears over a 20-day period confirmed the enhanced performance of the proposed sensor for agricultural instrumentation applications.