Design And Implementation Of Drying Materials’ Moisture Measurement System On Belt Dryer

Material’s moisture measurement is the main problem in drying process. It directly determines the efficiency of the finished product. But the traditional control method is setting a fixed drying time, it can’t assure moisture’s uniformity of drying material. This paper introduces an on line material moisture detection system, it can measure the moisture of drying material in real-time, and provide a basis for the automatic moisture control system.The moisture measurement system in belt dryer is based on the theory of lamber-beer’s law. It uses circuit system to drive infrared LED and coupled to the fiber optic. The infrared LED illuminates light to the measured material surface. According to light reflected by material, it can judge the moisture content through spectral analysis. The system is mainly composed of optical fiber sensing system, signal detection system and digital processing system. The infrared light couples to the optical fiber, and transmits to the material surface. At the same time the system collects the reflected light, and uses lens coupled to the receiving optical fiber. Detector receives the light which contains the moisture information and transmits it into electrical signal. On one hand signal detection system uses constant current technology to drive the infrared LED, on the other hand it receives the electrical signal transmited by detector. After amplifying, filtering, and choosing frequency, the system can get the signal which contains the true value of moisture, and convert it into digital quantity. Digital processing system calculates digital quantity and searchs the moisture data through the table fitted data curve form. It calls the display module to show the value in real-time, at the same time schedules modules to ensure the normal work of the system.System directly uses measurement method through infrared LED and probe. Data results show that the system’s maximum error’s absolute value is|△Wmax|=0.32%, and root mean square value is|△Wmax|=0.18%. Its repeatability precision is0.11%, and relative stability error is5.8%.