Improvement on System for Determination of Dielectric Properties on Agricultural Products

The present common microwave measurement system with the high cost is only suitable for a certain narrow frequency range,thus causing restrictions for the research work in this field.For this reason, a improved testing system based on the shortcircuited waveguide principle was developed and used for the practical measurement.The system is suitable for measuring dielectric properties of the materials of grain(soybean,wheat,etc.), small seeds of ornamental species and their ground powder. It is also suited to measuring complex relative permittivity　for biological materials including liquid or high moisture substance.　With “StatisticalAnalysisSystem(SAS)”and “curve inserting and fitting method”, combining the known dielectric equations,the needed dielectric data were obtained within the widest continuous frequency range. The research of optimumcombined parameters for dielectric heating treatment was speedingup.　The computer program makes it quite simple to use the measuring procedures of this system.It takes only about 30 minutes to complete all measurements for a single sample with certain moisture on about ten different densities and to perform all necessary calculations with the computer program for determining the values of dieletric constant and loss factor. The instruments are reason simpler, and more practicable. As a result,in comparison, the differences between these datum by this simplified equipment and those of USDA,U.S.Department of Agriculture,are within the range from 3 % to 5 % for the dielectric constant of ground wheat on two moisture levels,11 % and 17 %,at 10.51GHz and for the loss factor on 17 %.