便携式土壤水分测试系统设计

Design of a Portable Detector for Soil Water Content

土壤水分含量不仅对农作物生长有较大的影响,而且对越野车辆地面通过性也有重要的影响。设计了一种基于时域反射法的土壤含水量测试系统。通过直接数字频率合成器(DDS)产生电磁波测试其介电常数;然后利用介电常数-含水量经验模型得出土壤含水量。系统还配备了GPS接收系统,能记录每次测量的经纬度坐标,并且根据经纬度地名对照表在记录中存储相应的地名。系统通过扩展存储容量使测试记录数可达上万条,并且能通过串口把数据上传到计算机中进行进一步处理。该测试系统具有便携、快速、原位测量的特点,便于构建时空尺度的土壤含水量演变立体分布图,为车辆地面通过性判断提高依据。

The soil water content has a great influence not only to the growth of crops, but also to the off-road vehicle＇ s ground trafficability. A soil water content detector system based on time domain reflectometry is designed. It tests soil＇ s dielectric constant by the DDS producing electromagnetic waves, then uses dielectric constant - water content empirical model to educe the soil water content. The system also provides the GPS receiving system. It can record the latitude and longitude to coordinate each time, and to save the corresponding geographic name in the record according to the latitude and longitude geographic name comparative table. The system makes the record number reach ten thousand through extending the storage capability, and can upload the data to the computer through the serial port for a further processing. The test system has portable, rapid, insitu measurement characteristics, and is easy to construct the space-time-scale three-dimensional distribution of the soil water content evolution. It can help judge vehicle＇ s ground trafficability.