The Research On Capacitive Grain Moisture On-line Detector

Our country is a humongous but populous countries, our country is based on agriculturalproduction as the foundation of the national economy for thousands of years, it may say thatgrain as an important material is related to the whole country people’s livelihood. The moisturecontent of grain as an important index to measure the quality of grain, the grain in thetransportation, storage and processing production link is particularly important. Exorbitantmoisture content will not only increase the weight of the food, waste of transport capacity andstorage capacity, but also urge the life activities of grain more exuberant, cause the grainproduce certain biochemical reaction, lead to the deterioration. The low moisture content, Willdestroy the organic material of the grain, to reduce their weight. So, grain moisture detection isthe important basis to ensure each link of food security. Therefore, to measure the moisturecontent of grain accurately, and control it in a safe area is of great significance.This article mainly aimed at the problem of the grain moisture content in drying processonline and accurate detection, based on the correlation between grain moisture and capacitancesensor, developed a set of capacitive grain moisture online testing system。The main contents areas follows:(1)The structure and function design of the system. The overall structure of this systemmainly includes the capacitive sensors and grain discharging wheel device, the capacitive sensoris mounted on the back of a hollow plastic semi-cylinder, the sensor plate adopt the cross fingerstructure that located on the same plane. Grain discharging wheel device uses the single phaseAC motor as drive, through the rotation of the motor drives the grain discharging wheel isrotating at a constant speed, making the grain that in the moisture meter sampling containerdischarged uniformly. A complete set of capacitive moisture function of on-line detectionsystem mainly includes the moisture online dynamic detection, the grain temperature detection,computer digital display, automatic/manual work mode, the manual calibration, data storage,grain varieties switch, temperature compensation and grain wheel speed adjustment, etc.(2)The hardware design of the system. The hardware part adopts the modular designmethod,using STC89C52RC single-chip microcomputer as the core model, designed the hardwarecircuit of the system lower computer. Including power circuit, capacitance signalcollectioncircuit, temperature measurement circuit and serial communication circuit module.(3)The software and the function design of the system. The software system also used themodular design method, mainly consists of two parts, upper computer and lower computer. Among them, the lower computer procedure adopts single chip microcomputer C languageprogram, the program is mainly responsible for receiving the upper computer Instruction,collecting sampling frequency and grain temperature data, and through a serial port sent to thePC. It mainly includes the frequency of data acquisition, temperature data acquisition and serialdata transceiver module, etc. The upper computer using virtual instrument technology, usingLabVIEW software platform, set the computer to the upper machine is mainly responsible forcontrol of the lower computer, receive the data sent from the lower computer, to process anddisplay, and storage data.(4)The system calibration and the mathematical model of moisture detection. The grainmoisture detection is used in national standard as a benchmark, selecting a variety of corn asexperimental samples, to calibrate the system. For the frequency data that collected by thesystem to eliminating abnormal data and calculating average processing, and according to thenational standard oven method measured the moisture content to set up the mathematicalmodel. To determine the relationship between the system output frequency and water content incorn.(5)The performance test of the system. Install this system in the integrated experimentalplatform, for the stability and accuracy of the system proceeding experimental verification.Detected in the experimental data were analyzed, and concluded that the system stability is good,and the accuracy of moisture detection meet the requirements of relevant error.