Nelson Stuart O, Trabelsi Samir
U.S. Department of Agriculture, Agricultural Research Service, Richard B. Russell Agricultural Research Center, Athens, Georgia 30604-5677, USA.
J Microw Power Electromagn Energy. 2004;39(2):107-17. doi: 10.1080/08327823.2004.11688512.
The importance of cereal grain moisture content in determining time of harvest and in preserving grain quality is described. Techniques for moisture measurement, including electronic moisture meters, are also discussed briefly, and the need for better moisture sensing techniques for modern agricultural on-line moisture monitoring is described. Principles of microwave free-space measurements involving attenuation and phase-shift determination are explained, and density-independent functions of the grain permittivity are presented that permit reliable moisture sensing applicable to moving grain in which bulk density variation occurs. Three different approaches are discussed for determining moisture content and bulk density of grain from microwave measurement of the dielectric properties. A new moisture calibration function, based on complex-plane plots of dielectric constant and loss factor, each divided by bulk density, is described, which promises a universal calibration for different types of grain and seed. This important advantage should encourage commercial development for practical use.
描述了谷物含水量在确定收获时间和保存谷物质量方面的重要性。还简要讨论了包括电子水分仪在内的水分测量技术，并阐述了现代农业在线水分监测对更好的水分传感技术的需求。解释了涉及衰减和相移测定的微波自由空间测量原理，并给出了谷物介电常数与密度无关的函数，该函数可实现对发生堆积密度变化的移动谷物进行可靠的水分传感。讨论了三种通过微波测量介电特性来确定谷物含水量和堆积密度的不同方法。介绍了一种基于介电常数和损耗因子复平面图（均除以堆积密度）的新水分校准函数，该函数有望对不同类型的谷物和种子进行通用校准。这一重要优势应会推动其商业化开发以供实际应用。
