Design On Straw Water Content Meter Based On SCM

Straw is an important biological resource in the crop production system. Human usestraw for a long time. With the transformation of traditional agriculture to modern agriculture,the utilization technologies of straw present a diversified development trend. Water content isan important reference index for many utilization technologies of straw. Water content affectsthe storage and some of processing links of straw, and sometimes even determines the qualityof its finished products directly, therefore the detection of straw water content is veryimportant. However, existing detection equipments of straw water content are less and tooexpensive, and traditional drying method has many shortcomings, such as long detectionperiod, not continues measurement, to some extent, water content restricts the utilizationefficiency of straw. So, it is quite necessary to develop a straw water content meter withsimple and convenient operating, low price, quickly and continuously measuring. Summariedthe results of existing non-destruction testing methods of water content of agriculturalmaterials, a straw water content meter, based on capacitance detection method and AT89S52microcontroller as core, has designed in this paper, it achieved the detection of straw watercontent by the prediction model of water content.The main tasks and results of this paper areas follows:(1) Studied the impact of water content on comprehensive utilization technologies ofcrop straw, put forward the design method of the capacitance detection method, and made anin-depth analysis on the basic principles and related factors(temperature, bulk density, etc) ofcapacitance detection method. Then the theoretical basis of the straw water content meter wasestablished.(2) The hardware system of the meter, as the core of AT89S52microcontroller, wasdesigned. Firstly, designed the parallel plate capacitance sensor, it used to detect capacitance,DS18B20temperature sensor used to detect temperature, and FSR402pressure sensors used todetect bulk density indirectly. Then, the hardware circuit was designed, it includes detectioncircuits of capacitance signal, temperature signal and force signal, circuit of A/D conversion,SCM controling, liquid crystal display, function keys. Finally, the hardware circuit board ofthe meter was manufactured.(3) The software of the meter was written in C language. It includes system's primary function, A/D conversion, temperature acquisition, liquid crystal display and water contentcalculating, etc.(4) The straw of wheat was used as experimental subject to study the change law of itscapacitance, water content, temperature and bulk density. A prediction model of straw watercontent was established, and the results of validation proves that the determination coefficientof the model is0.987.(5) The detection performance of the meter was verified by experiment. The results showthat: compared drying method, the meter's water content detection error is in±2.2%,response time is2s at the water content from10%to20%, temperature from5℃to35℃, andit has good application prospects.