| 摘要 |
PURPOSE:To reduce measurement errors by forming a feedback loop in such a manner that the surface potential of the conductor provided to a drum equals to the surface potential of the drum. CONSTITUTION:When the surface potential Vx of a drum 1 and the surface potential Vs of a conductor 4 differ, the potential of that difference is taken out as the output of a phase synchronizing detector 7, and the output of a rectifier 8 is applied to the conductor 4. Hence, as the drum 1 rotates, the difference between the surface potential Vx of the drum 1 and the surface potential Vs of the conductor 4 diminishes until finally both potentials equal. The output of the rectifier 8 is connected to the conductor 4, and since the surface potentials Vx, Vs of the drum 1 and the conductor 4 are equal, it results in the end that an indicator 9 indicates the surface potential Vx of the drum 1. Then, a minor deviation of the distance between the drum 1 and an inductive electrode 2 is of no problem, and it turns out the electrode 2 is only required to detect the surface potential Vx of the drum 1. |
