Design and Performance Analysis of Composite Sensor for Multilayer Soil Profile

Abstract:

Considering the many difficulties of installing the sensor for the soil temperature and moisture measurement, such as miserable installation of the sensor and relatively large disturbance to the local soil, this paper designed a composite sensor for multilayer soil profile in accordance with the principles of soil moisture measurement and temperature measurement based on SWR and platinum resistance. A vector network analyzer and HFSS electromagnetic simulation software were used to analyze impedance characteristic and electric field distribution of the sensor electrode. According to the analysis result, the structure of copper detection probe was designed. The diameter of the probe is 5cm, the width is 2.5cm, the thickness is 0.09cm and the excitation frequency of test circuit is 100MHz. Three types of soil were choosen as experimental samples. The polynomial fitting and linear fitting were conducted on the output values of sensor detection unit. The results correlation reached more than 099.The static and dynamic performance of the system met the detection requirements of temperature and moisture of soil profile. Experiments was carried out in Xiaotangshan District, Beijing City, and then effect of temperature and volumetric moisture content of soil on sensor outputs were analyzed and correction models were established by using the statistical regression method at different temperatures. The sensor working in the PVC pipe buried in the soil could obtain the information of temperature and moisture of the three layers, and its performance was stable and the data was reliable. This study provides a highly efficient method for obtaining the realtime information of multilayer soil moisture and temperature.