| Soil moisture measurement is given close attention by architecture, agriculture, botany, ecology and many other subjects. The method is various, and each method has its own advantage and application range. But soil has extremely complex properties itself, so each method has many unsatisfactory aspects. This thesis introduces various traditional soil moisture measurement methods, and every method is compared with each other at first.Terahertz refers to the electromagnetic wave whose frequency is at 0.1~10×1012 Hz. Because of its new characteristics, the wave has been more and more noticed. Terahertz wave can penetrate many kinds of dielectric and nonpolar liquid, and it's harmless to humans. Water is a kind of polar liquid, which can strongly absorb terahertz radiation. Therefore, when the radiation penetrate soil it will be influenced by the moisture. Although soil can absorb part of THz radiation, that's much weaker than the moisture do. So the method of measuring the moisture content of soil with THz radiation is feasible in theory.Compared with high frequency radio wave and microwave, THz wave has much shorter wavelengths and can improve measurement accuracy and resolution. Compared with high-energy rays and particle, it's harmless to human and no environmental pollution, so it is a kind of ideal of soil moisture measurement method. This research has established a set of measuring method for soil moisture based on time-domain spectroscopy and has provided the computing method and function based on THz spectral transmission. The result is got by means of high accuracy soil sample holder and many quantitative experiments. Compared to weight method, the measure results show that the method is quick and effective, harmless, easy to operate, and the global error is less than 3%, the mean value is approximately 1%, affected by region alteration lightly. |
PDF Full Text Request