| Grain condition monitoring system is one of the four new technology of grain storage, which can supervise grain condition, store and analyze data by using modern computer and electronic technology, and thus can control grain storage facilities timely. It has the function of rain condition detection, grain condition analysis and grain condition control. Among them, grain condition detection is the basis, grain condition analysis is evidence and grain condition control is the means. Grain inspection technology research in China started late, most of the current detection system is simple, which can only detect the grain temperature and air relative humidity, and the minority can detect pests, gas, grain moisture and other parameters. But this kind of system is not compatible with each other. If it is necessary to detect a variety of grain condition parameters, we need to install the corresponding detection system of several functions, and thus increase the cost of installation and maintenance. According to the above problems, this paper presented a set of real-time multi-parameter monitoring device which integrated grain temperature, relative humidity, moisture content of grain in one reactor, and thus can calculate the grain balance moisture and communicate with the host computer. This device is verified to meet the requirements of multi-parameter detection of grain condition by test.The main contents are as follows:For the characteristics both of bins and grain, it analyzed the overall demand of means, determined the grain moisture detector as the main design, and selected the capacitance method as grain moisture detection method.In structure, the mechanical structure of a capacitive sensor had been improved to make it more useful in the grain bulk environment. The constant pressure protection shell was fitted at the upper end of the sampling vessel, by which the equipment could protect the grain in the sample container from outside pressure,make the grain porosity maintain a constant,and eliminate the effect of the cumulative effects of time to ensure the accuracy of test results.The thesis designed and implemented the grain situation multi-parameter monitoring devices based on STC89C52 micro-controller which as the core. The hardware designed through modular approach, and which had achieved the integration of moisture measurement, temperature and humidity measurement module. The system used a differential data line transceiver converted common-mode data transmission format to differential mode transmission, which improved data transmission distance and stability.The functions of the detection of grain moisture, temperature, relative air humidity, and real-time calculation of the equilibrium moisture content of grain had been realized. And each of lower machine had been given the address, host computer using inspection ways gather grain situation of each parameter. In addition, the host computer would simply process, correct and display the received data.National measurement standard method of test grain moisture and several tests had been combined; the system used a single calibration factor method to establish the corresponding mathematical model for temperature compensation of grain moisture.The author proposed a monitoring device without food quickly fine-tune the ways in which all devices within a certain range of grain moisture, temperature and humidity parameters are detected sufficiently approximate, elimination of bias since the inter-device hardware circuit welding and mechanical structure mounted on the test results, achieved inter-device compatibility function.Small intelligent ventilated storage barn eree used for a long test, the stability and accuracy of the system and other systems static characteristics were verified by experiments. The experimental data were analyzed. It was concluded that the system stability was good, and the accuracy of parameters detection met the requirements of relevant error line with the requirements of the conclusions. |
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