On-line Measurement System of Grain MoistureContent Process in Grain Dryer

摘要

An on-line measurement system was developed for the purpose of measuring andcontrolling the grain moisture content from the outlet of a dryer during drying process. Concentriccylinder type of capacitance sensor was used to measure the capacitance, which varied with thechange of the moisture content and the dielectric constant of grain. The relationship between grainmoisture content and oscillation frequency of the sensor as well as grain temperature under uniformflow was determined, and a mathematical model was the developed. In order to achieve the requiredgrain moisture content, the PI control algorithm was used to control the unloading augur speed.Tests were conducted with wheat and corn. The experimental result showed that control accuracy atthe dryer’s outlet was within 0.5% of the required moisture content.