A multiple-rod TDR probe development with a view to measure water content and electrical conductivity(EC) of surface soil.

研制了一种多杆式时域反射（TDR）探头，用于测量表层土壤的含水量和电导率。探头由几个三杆探头组成，其中每个三杆探头的外杆是相邻探头的公共电气接地导线。因此，相邻的三杆探针之间没有额外的空间。这种探头配置使TDR测量能够在现场大面积延伸。多杆探头的特性进行了检查，在一个容器中的沙子1。1米×0. 81m×0.二十米首先，一个单位的探头组成的三个1米长的钢棒的0。测试了直径为5cm、棒间距为10cm的探针对砂土中水分和EC的检测性能。然后，将由七根杆组成且具有相同探针规格的多杆探针水平插入容器的沙子中表面以下10 cm处。在蒸发试验过程中测量了沙子的介电常数和EC。由于TDR测量取决于探头采样体积中的空气体积，因此单元探头测试揭示了介电常数对探头插入深度的依赖性。一个三次表达式，如托普的一个，提供了一个很好的关系，平均含水量和介电常数的表层土壤。然而，插入深度不影响EC测量。此外，多杆探针，通过蒸发试验，准确地测量了水分含量和EC的变化超过0。88 m^2在地表区域。因此，我们的研究结果表明，多棒TDR测量系统扩展到更大的区域，使遥感数据更准确的可能性。

A multiple-rod TDR probe was developed with a view to measure water content and electrical conductivity(EC) of surface soil. The probe consisted of several three-rod probes in which the outer rods of each three-rod probe were the common electrical earth guides for the adjacent probes. There was thus no extra space between the adjacent three-rod probes. This probe configuration enabled the TDR measurement to extend over a large area in the field. The characteristics of the multiple-rod probe were examined in sand in a container of 1. 1m×0. 81m×0. 20m. First, a one unit of probe consisting of three 1-m long steel rods of 0. 5 cm diameter with a spacing of 10 cm between the rods was tested for its detective performance for water and EC in sand. Then, a multiple-rod probe consisting of seven rods and with the same probe specifications was inserted horizontally in the sand of the container at 10 cm below the surface. The dielectric constant and EC of the sand were measured with during an evaporation test. Since TDR measurement depended on the air volume in the sampling volume of a probe, the unit probe test revealed the dependency of dielectric constant on the insertion depth of the probe. A cubic expression, such as the Topp' s one, provided a good relation between the average water content and dielectric constant of the surface soil. The insertion depth did not however affect the EC measurement. Moreover, the multiple-rod probe, through the evaporation test, accurately measured the change in water content and EC over 0. 88 m^2 in the surface region. Our results thus showed the possibility of extending the multiple-rod TDR measurement system to a larger area to make the remote sensing data more accurate.