【作者】 王一鸣； 王克栋； 杨卫中； 董乔雪； 冯磊；

【Author】 Wang Yiming, Wang Kedong, Yang Weizhong, Dong Qiaoxue, Feng Lei (College of Information and Electrical Engineering, China Agricultural University, Beijing 100083, China)

【机构】 中国农业大学；

【摘要】 本文介绍了一种新的基于相位检测的时域反射土壤水分测试仪。使用单一频率的正弦信号代替阶跃信号、使用相位检测方法代替高速采样示波器方法。相位检测器将入射信号和反射信号的相位差转换为与之成正比的直流电压信号,通过测量该直流电压信号即可得到电磁波在探针上传播的时间,通过标定可进一步得到土壤含水量。在同轴电缆中的测试表明该系统在时间测量上有很高的精度和稳定性,通过标定后在壤土中的土壤水分测量结果与烘干法测量的结果差别不超过0.03m3/m3。更多还原

【Abstract】 A new TDR soil moisture measuring instrument based on phase detect is proposed. In the instrument Single-frequency sinusoidal voltage signal was adopted as test signal to replace voltage pulse with very short rise-time, and phase detector was used instead of high-speed sampling oscilloscope. Phase detector transforms the phrase error between reflected signal and incident signal to a DC voltage, which is proportional to phrase error. The travel time of test signal along the probe embedded in moist soil will be obtained by measuring the DC voltage, and after calibrating the instrument it can be used to measure the soil moisture. The instrument was detected in testing the length of a coaxial cable, and the result show that the instrument is good at measuring accuracy and stability. Using the instrument to measure the soil moisture in loam soil, the measurement error was less than 0.03 m3/m3 comparing with the measuring value with gravimetric method.更多还原