Inversion Study On Detecting Wheat Moisture Content Outside The Granary By Electromagnetic Wave

Grain storage security is an important part of security. The moisture content of grain not only is an important aspect of surveillance, but also is one of the important quality indicators for the safety of grain storage. This paper puts forward to adopting the GPR to detect the moisture content of wheat outside the granary according to strong penetrating and high resolution characteristics of electromagnetic wave, in view of various drawbacks of the grain moisture measurement using Humidity Sensor. There have deeply studied the relationships between dielectric constant and moisture of wheat and inversed the moisture content of wheat with mathematics model.In this paper, the propagation characteristics of electromagnetic wave through the wall is researched and the forward model for the electromagnetic wave propagation in the granary system is established based on the fundamental theory of electromagnetic and working principle of GPR through analyzing the influences of the real part and imaginary part of dielectric constant on reflected the electromagnetic wave. Applying this forward model, the system identification method is presented for backcalculating the dielectric constant of hall pavement structures. Furthermore,two mathematics model of dielectric and moisture are established with the analysis of the relationships between temperature, frequency, density, especially moisture and dielectric constant, which one is square root model, and the other one is Q-value linear model. The comparison results between these two models and actual measuring value shows that the former is more suitable the moisture detection with electromagnetic wave in granary. Finally, An experiment that used advanced Italy RIS-K2 GPR to measure dielectric permittivity and moisture content in the No.5 barn of western suburb grain in Zhengzhou City is carried on to refitting the coefficient of square root model, from which it can well coincide with actual measuring value.The result proves that inversion model with electromagnetic wave has high precision, and also verifies that using the GPR to survey moisture content of storage wheat outside the granary is a scientific, effective and rapid method, which can further popularization.