丰富而准确的土壤墒情信息对研究水循环变化规律、水资源合理利用、农林牧业精准灌溉和抗旱救灾等工作发挥重要作用。而现今我国土壤墒情检测主要依靠经验估计， 墒情信息获取难度大且准确性差。随着数据通信技术的发展，将无线通信技术、计算机网络及土壤检测技术结合起来实现对土壤墒情的准确智能检测是大势所趋。 本文对比了国内外土壤墒情检测方法的优劣，选定频域反射法（FDR）为土壤墒情检测实现方法，以S3C2440A为嵌入式处理器，Linux为嵌入式操作系统提出了土壤墒情传感器的设计方案。该传感器由模拟信号输入模块、信号处理模块、显示模块、存储模块、通信模块和供电单元组成，模拟信号输入模块实现墒情信息与电信号的转换，由LC谐振电路、128分频电路、波形转换电路、滤波电路和信号放大电路组成。在嵌入式Linux平台上，完成u-boot的修改，kernel的定制和root的构建，并将其移植到传感器上。基于Linux软件开发环境实现传感器驱动和测试功能。 对FDR土壤墒情传感器进行实地测试，测试结果表明，该传感器能够准确测量、显示土壤墒情，并且将其通过3G模块，以PDU格式发送至终端设备，具有高精度、高灵敏性、高实时性和操作便捷等特点。

Rich and accurate soil moisture information plays an important role to the study of change law on water cycle, rational utilization of water resources, precision irrigation on agriculture, forestry and animal husbandry and drought relief work. But now soil moisture detection relies mainly on the empirical estimates, having great difficulties and poor accuracy in soil moisture information acquisition in China. With the development of data communication technology, the general trend is to combine the wireless communication technology, computer networks and soil detection technology, to realize detection of soil moisture information. This paper compares different soil detection methods in China and abroad, chooses frequency domain reflectometry(FDR) to realize the soil moisture detection, and proposes the design scheme for soil moisture sensor with S3C2400A as the embedded processor and Linux as the embedded operating system. The sensor is composed of analog signal input module, signal processing module, display module, memory module, communication module and power supply unit. The analog signal input module implements the conversion of moisture to electric signal, which consists LC resonance circuit, 128 frequency dividing circuit, waveform conversion circuit, filtering circuit and signal amplification circuit. The paper sets up the embedded Linux platform, modifies the u-boot, customs the kernel, constructs the root and transplants them to the sensor.Based on the Linux software development environment, the sensor driver and testing procedures are designed and completed. The field testing result of FDR soil moisture sensor shows that the sensor could measure and display the moisture precisely, and transmit the moisture to terminal equipment in PDU format through 3G module.It has the properties of high accuracy, high sensitivity, high real time capability and convenient operations.