Research Of Moisture Detection Method And Device Based On Microwave Technology

The presence of water affects all aspects of human life, from people’s dailylives to the industrial and agricultural processing. The detection and control ofthe moisture content of the substances has been an important scientificresearch direction, including storage and transportation of food, tobaccoprocessing, pulp and paper, mining of coal stone, soil testing, fertilizerproduction, wood processing, textiles, concrete mix and oil processing industry,etc. This subject starting from the material moisture content testing, develop amethod and device, which can achieve the moisture content in the way ofhigh-precision and non-destructive testing.The conventional methods of moisture detection include resistor, capacitor,neutron, infrared and microwave method. Those detection methods aredifferent from technical characteristics, scope, and measurement accuracy. Atmicrowave frequencies, the water will cause the polarization oscillation. Themicrowave transmission will produce the role of reflection, transmission, andscattering. Therefore, the material moisture content can be determined bymeasuring the microwave parameters. The moisture detection device usingmicrowave space technology cannot have to direct contact with the testedsubstances in the measurement, which is the most easy to implement on-linemoisture content non-destructive testing.The experimental subject applied microwave emission wave and thereflected wave mixing technique to the detection of moisture content,discussed the overall structure of the microwave moisture measuring devicesand units. For the probe of the microwave moisture detection device the paper start from the microwave space wave technology, analysis the impact ofmaterial moisture content on the dielectric constant of the medium, microwavereflection, transmission power attenuation, and research each part of themicrowave moisture detection device such as Signal units, isolators,attenuators, mixers, microwave waveguides, microwave transceiverwaveguide antenna and the signal processing unit.In the signal processing unit, for different application requirements ofonline real-time detection of moisture content, the real-time and meansampling mode and the output voltage and current control mode was designed.To achieve the above functions for the device, the hardware and softwaredesign process was analyzed and discussed, which include the power supplymodule, the mean signal processing circuit modules, analog-digital conversionunit, micro-controller, digital to analog conversion unit, mode select control unit,LCD and output mode selection unit.The moisture detection device based on the design and development ofmicrowave technology, with a novel structure, easy operation, andmeasurement of high precision, wide range of applications, anti-interferenceability, can achieve the online non-destructive continuous and low costmeasurement, which have broad application prospects in the industrial andagricultural production.