Research And Design Of Microwave Moisture Measurement System Based On Six Port Technology

In industrial and agricultural production process,the water content has important influence on the quality of product,therefore,water testing and monitoring is of great significance.Compared with the commonly used method of measuring moisture content,microwave detection method can achieve real-time online and nondestructive measuring.Are analyzed in this paper based on the technology of six-port microwave test material moisture content test method,developed a fast-nondestructive measuring moisture content of material test system.The main work of the thesis is as follows:1.A six-port reflectometer was developed.The six-port reflectometer consists of a six-port circuit,a detection circuit,and a data acquisition circuit.The six-port circuit consists of a directional coupler and a symmetrical five-port circuit.The six-port circuit,detection circuit,and data acquisition circuit are mainly designed.And a calibration program and the moisture content calculation program was written.The measured results meet the testing needs.2.Open waveguide sensors were theoretically analyzed and designed.Because theoretically the flange size is infinite and the sample to be tested is infinitely thick,the above two conditions cannot be achieved in practical tests.This paper analyzes the influence of the size of the flange and the thickness of the sample on the measurement of the open waveguide method and determines the size of the flange and the minimum thickness of the sample with certain accuracy.3.With the moisture content test system of sand and gravel,crushed corn moisture content was tested.Analysis of the reflection coefficient-water cut curve of the BP neural network approximation and polynomial fitting method and compared the advantages and disadvantages of two methods in moisture content measurement.4.Emphatically discusses the effect of the temperature of the material to the measurement result,based on the experiment,the temperature affects the moisture content of calculation model for the correction.5.On the performance of the test system,measuring precision and error are analyzed,the results show that the test system can realize real-time,on-line measurement.