Research Of Measurement Technique On Soil Water Content Based On Dual-frequency Alternate

With the rapid development of information and artificial intelligence technology, such precise agricultural production management thoughts as the positioning management on crops and on-demand inputs on crops has gradually occurred,eventually forming the concept of precision agriculture.Anextremely crucial part in precision agriculture is to obtain all kinds of parameters of the soil, including soil organic matter content, soil conductivity, soil moisture, soil compaction etc,of which the soil moisture content is indispensable.At home, instruments used to detect soil moisture content are portable on the whole.However, new requirements are occurred in the new era. This paper aims to design in-vehicle soil moisture detection system.The testing methods of soil moisture content are basically as follow:touching appearance and weighing method, the tension meter method and resistance method, neutron method, remote sensing method, time domain reflection method, frequency domain reflection method, standing wave ratio method, capacitance sensor method, etc.But some of them can only be applied in the laboratory; some have good performance, but are very expensive; others are not suitable for vehicle. According to the practical situation and based on capacitance sensor method, in-car soil moisture detection system is designed. Obviously, capacitance sensor method possess many advantages,such as easy to build, suitable for vehicle, simple to install and operate etc.Based on the capacitance sensor method, we puts forward three kinds of detection methods:additional resistance method, Ac/dc alternate method and dual-frequency alternate method, and gives theoretical analysis and mathematical deduction of them.After comparative analysis,dual-frequency alternate method is applied to measure soil moisture content.First of all, obtaining the value of the soil moisture content on the basis of fitting curve between soil moisture content and by measuring and calculating the equivalent capacitance. Based on the above principle, the author has developed a car soil moisture detection system, which is easy to operate and can realize the measurement of in-car soil water content. It also possesses rapid response speed,high accuracy, directly-displayed test data, and can be transmitted to PC.In order to further prove the feasibility of this method, field test was conducted in Long Kang Farm, huai yuan county, Anhui province.The results show that it is more accurate to detect the soil moisture content by using this method, and the equivalent capacitance of soil moisture content and soil can be approximately fitted to linear relationship.