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

为了测量表层土壤的含水率和电导率，研制了一种多杆TDR探头。该探头由多个三杆探头组成，其中每个三杆探头的外棒是相邻探头的公共电气接地导轨。因此，相邻的三杆探头之间没有额外的空间。这种探头配置使TDR测量能够扩展到野外的大片区域。在一个1.1m×0的容器中，在沙子中测试了多杆探头的特性。81m×0。2000万。首先，一个单元的探头由三根1米长的钢棒组成。测试了直径为5 cm、棒间距为10 cm时对沙子中水和EC的检测性能。然后，将一个由7根探头组成的相同探头规格的多杆探头水平插入到容器表面下10厘米处的沙子中。在蒸发试验中测量了砂子的介电常数和电导率。由于TDR测量依赖于探头采样体积中的空气量，因此单位探头测试揭示了介电常数与探头插入深度的依赖关系。表面土壤的平均含水率与介电常数之间有很好的对应关系，如Topp的S公式。然而，插入深度不影响EC测量。此外，多杆探头通过蒸发试验，准确地测量了含水率和电导率的变化。表层88m^2。因此，我们的结果表明了将多杆TDR测量系统扩展到更大的区域以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.