A grain moisture model based on capacitive sensor

Abstract

This study starts with the principles of the variable dielectric-type cylindrical capacitive sensor, conducts the theoretical analysis after dielectric is divided into three phases (solid, liquid and gas), determines the relation between dielectric constant and other influence factors through the least squares fitting method, makes compensation for such factors as temperature, grain variety and air void ratio, builds the mathematical model of grain moisture content(GMC) through the variable dielectric-type cylindrical capacitive sensor, and suggests the capacitance measurement method based on pulse-width modulation. The experiment result shows that the suggested capacitance measurement method can accurately measure micro-(pF-class) capacitance, and the theoretical value of GMC as produced by this mathematical model falls within an allowable error range when compared to actual value, so this model proves to be rational.