Research On Moisture Measurement Of Granular Materal With Microwave Method

Microwave is a spatial electromagnetic wave, which can spread freely in the space and has the characters of electric field and magnetic field. The water content of the granular material affects the efficiency and cost of production, so it has the important sense to measure the water content. Because the dielectric constant of water and the dry matter have a great difference, it will be affected by the water content, so as to measure the power attenuation, the phase alter, the resonance frequency and so on as the related physical quantity, can measure the water percentage. This paper discusses the microwave measurement to measure the moisture of the powder. At the same time, the theory of microwave measurement and some kinds of microwave devices so as to its operation principle is introduced.Because the dielectric constant of water is greater than others, the attenuation of microwave through the waver content material is caused by water, measuring the power of the microwave after attenuation, the water percentage is gained, This is the theory of microwave attenuation moisture measurement. Using the microwave surge source, isolator attenuator, and the beaming receiving antenna to build the microwave attenuation moisture measurement system. Based on the microwave transmission attenuation measurement, the moisture experiments of the grave and the limestone is accomplished, the polyfit equation about these two material moisture and the measured output voltage signal is achieved, the causes of the error is analyzed, design the measurement circuit, finish the diagram and the PCB board.The reflected microwave carries the material water content information The reflected wave and the incident ray interfere the standing wave which forms to contain such information similarly mutually. According to the above proposed the application reflection method survey standing-wave ratio surveys agglutinates the material water content. Through the experiment, proposed the survey standing wave maximum value method measures wet. Differently containswater after the survey the material reflection standing wave maximum value to appear the position and the maximum value voltage. The analysis result recording indicated the survey is feasible. The innovation active poke head in the law to apply to measures wet center. Active pokes head in the operating current direct component to receive the load the influence. The different moisture content material took when load to the influence which pokes head in is different Found the material moisture content through the experiment and active pokes head in the d c operation electric current relations.