Online Moisture Test System For Grain

Grain counts for much for the national economy and people's livelihood. To solve the problem of lack of grain, safe storage of grain is an effective measure besides enlarging area of plantation and increasing its output by unit acreage.During the process of grain storage, grain dryness is a critical procedure, which in fact is a continuous process. The flow of grain dryness is as follows: put the grain being treated into drying tower; after process of warm-up, drying and cooling to normal temperature, when the moisture of grain is 14%, which is safe moisture, it is time to be expelled from the drying tower. During the above drying course, the core technique is the online test and control technology, which can restrict performance of the drying system. However, some conventional methods for grain storage do not work well in online test due to the complicated condition factors.At present, some lagging manual test is still being used in some grain moisture inspection, while other test mainly relies on imported equipment. Most of comprehensive testing equipment for grain moisture focus on laboratory or portable testing ones, such as fast moisture tester, microwave moisture tester, and so on. While the online testing equipment occupies a minimal scale, and there is not an automatic testing system available during the grain drying process.Such separate products as sensor and tester have been awarded with patents in China, and the testing methods can be classified into direct and indirect ones with testing principles based on resistance, capacitance, microwave, neutron source, weight-test, etc. While the offline method is suitable for laboratory usage with high accuracy, the online test method is not complete for function unavailability of data collection and control.This paper has made research on testing methods, moisture sensor, data collector and controller, software and database system according to the present condition for moisture test and drying equipment.After the comparison of practical performance of different testing systems, we focus on an online moisture test system for grain, in which cylindrical moisture sensors are put at the entry and outlet of the drying device. When the capacitance of moisture sensor changes aroused bygrain moisture change, and the changing signals are collected, transformed and conditioned, the system accomplishes its online real-time task of measurement. The moisture sensor makes digital modulation and compensation on signal non-linearity and temperature offset by adoption of microprocessor. The feedback signals are used to control frequency transformer and subsequently control the rotate speed of grain discharging device. As per requirements, the system can print many variables to realize the control function for level and temperature and alarming function.We have made a deal with Tieling City Grain Research Institute to establish an online test system for grain moisture inspection. The system can be jointly used with drying tower or other drying equipment to realize online automatic control. Therefore, grain drying efficiency and grain storage quality is greatly improved, and ultimately, we will capture the domestic or even overseas market.This paper only makes research on establishment of testing methods and sensor, and detailed research on data collection and control is to be continued on next stage.