对充氩气的弗兰克-赫兹管各个电极电流的测量发现，实验中阴极发射的电子绝大部分被第一栅极和第二栅极所吸收，只有很少的一部分形成了板极电流；第一、二栅极电压对阴极发射电子数量具有显著影响；第一栅极不但能吸收电子，在一定条件下还能发射电子. 本文给出了F-H曲线随第一栅极电压先增大后减小的直接原因，以及F-H曲线谷值电流不为零的电子能量分布解释.

 The measurement of the electrode current of argon-filled Frank-Hertz (F-H) tube shows that most of the electrons emitted by cathode are absorbed by grid1 and grid2, and only a small fraction forms the plate current. The grid1 and grid2 voltages have a significant influence on the number of electrons emitted by the cathode. Grid1 can not only absorb electrons, but also emit electrons under certain conditions. The direct reason why the F-H curve first increases and then decreases with grid1 voltage is given. The explanation of electron energy distribution with non-zero valley current of F-H curve is also given.