Optimization Design And Algorithm Research Of Microwave Moisture Measurement Sensor

Moisture is the percentage of weight of water in solid or liquid materials,which is one of the most important parameters.While moisture has a significant impact on the performance of materials,so it is very meaningful to measure moisture of material quickly and accurately.Only when the moisture of material is measured quickly and accurately,can the production efficiency controlled and optimized.Microwave method is a promising measurement method so many advantages,which means it is suitable for the realization of online and continuous nondestructive testing.Relevant literatures on moisture measurement were reviewed and the relevant measurement methods were classified.Comparing the advantages and disadvantages of measurement methods,we finally choose microwave resonance method for moisture measurement.Based on the microwave resonance method,the microstrip resonance ring(MRR)is used for measurement.Relevant formulas are used to calculate the substrate material,microstrip line width and other parameters.Then CST software is used for structural design,and the measurement process is simulated.The empirical curve fitting formula is used to connect the obtained f and Q with the required real and imaginary parts of the complex dielectric constant.PTFE and plexiglass block are used to verified the measurement system The measurement error of the dielectric constant was obtained by comparing with the standard value.In this paper,the resonant frequency f and Q of the resonant cavity are connected with the real and imaginary part of the dielectric constant of the material under test by curve fitting.The curve was verified under the conditions of basic mode and higher mode.Polytetrafluoroethylene(PTFE)and plexiglass block were put into the measurement system,and the measurement error of the permittivity was obtained by comparing with the standard value.The experiment was designed and the complex dielectric constant of MCC and soil was measured.At the same density,the relationship between material moisture and resonant frequency can be obtained.The complex dielectric constants of materials were measured in the basic mode and higher mode.It can be found that when the density changes,both the real part and the imaginary part of the dielectric constant change with the density to a large extent,and the influence of density cannot be excluded to measure the moisture of materials.According to the dielectric constant mixing principle,the density independence algorithm based on two-parameter method is adopted in this paper.Compared with the affect of moisture,the algorithm is less affected by density,which can effectively eliminate the influence of density on the measurement of moisture.Based on the measured data of MCC and sand,the density-independent operator is calculated,and the functional relationship of the operator with moisture is obtained.The measurement results of fundamental mode and higher mode are analyzed,and the method of extending the application range of the operator is obtained.The accuracy of the sensor is obtained based on the analysis of measurement errors.