樹木の接地インピーダンス測定法

抄録

This paper describes a method for measuring earth impedance of a tree. As the tree grows, its root well advances in the ground. A grade of the advance may be monitored by measuring the earth impedance of the tree, defined in the fields of electrical engineering. However, the method directly measuring the value has not been developed. The method presently available for measuring the earth impedance of a metal conductor cannot apply to the tree. Because electrode impedance of an electrode using for connection between the measurement circuit and the tree, brings serious error in the measurement. To avoid the effect of the electrode impedance, a circuit connection is newly devised which makes it possible to measure earth impedance of the tree directly. Further, equipotential surface within the trunk is adjusted to be parallel to the ground level by planting the trunk with several current-electrodes. This transaction assures accurate measurement for the cylindrical and semi-conductive object such as trees. Materials used in the experiments were zelkova tree, cherry tree, and silk-tree. Their girths are 1.7-2.0 meters. Obtained results from the experiments were 58.5-103.6 Ω in absolute value, and they showed slight capacitive reactance. It is concluded that the presented method is available for the measurement of earth impedance of the tree.