After studying the relationship between the moisture content of crops and their relative permittivity, the principle of capacitive sensor and the research results of measuring micro-capacitance, this paper summarizes the theoretical basis of dielectric properties of grain, the dielectric properties of wheat, corn and rice, the relationship between the dielectric properties of these crops and their water content. With these theory analyses, the paper gives a full look on the grain moisture detection system by the means of dielectric properties, which consists of six parts, a cylindrical capacitor, signal conditioning circuits, single-chip control module with an A/D converter, temperature detection module, keyboard module and display module. The system is simple, and can adapt to extreme environment and accomplish the rapid detection in manufacturing. A description is given of the principle, its hardware circuit and software programming flow chart.
RF noise driven dipole mode parametric resonance
