| Moisture content in food grade and quality is very important index,which is one of the grain index of a variety of detection.At present,the grain moisture content measurement in general can be divided into two kinds.One is direct detection and the other is the indirect method.Direct method namely drying method is also known as constant weight method.Through thermal drying method,the quality changes before and after drying as standard method,the moisture testing but long measurement time,power consumption is large and it is not conducive to rapid on-line detection in real time.Indirect agglutination test is detecting and grain moisture content change related physical quantities,which grain moisture content are obtained.Therefore,it is necessary to develop a high precision and repeatability grain moisture content measurement instrument.Based on the research of the grain dielectric constant and indirectly measuring grain moisture content is the core of this article.Grain dielectric constant,not only is determined by the moisture content of grain,grain type and environmental factors such as temperature and bulk density.Taking MC1648 P as LC oscillation circuit,voltage controlled oscillator by testing in the grain before and after the change of capacitance value.Matlab simulation is carried out on the capacitance-moisture content and add temperature compensation function.And the weight function of moisture contents for the correction.With the STC12C5A60S2 microcontroller as the control chip to realize frequency and capacitance conversion,color screen communication and printing,etc.Through Altium Designer software on the whole circuit design.With Japan PM8188-A comparison of grain moisture measuring instrument,the same grain moisture error less than 0.5%,which meets the accuracy requirement of the instrument. |
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