| 摘要 |
PURPOSE:To provide a surface electrometer which permits measuring an electric potential on the surface of a photosensitive drum in a copier stably and being installed in a copier easily, by feeding back a measuring voltage for a surface electric potential to a chopper electrode and a shield electrode. CONSTITUTION:A line of electric force based on an electric charge on the surface of a photosensitive drum 47 advances through a slit 88 to reach a measuring electrode 85. A chopper electrode 83 provided between the slit 88 and electrode 85 is adapted to induce an AC voltage on an electrode 85, which voltage crosses the line of electric force owing to the oscillations of a tuning fork 82 and has an amplitude in proportion to the difference between a voltage on the surface of the drum 47 and a voltage in the electrode 83. This AC signal is subjected to signal conversion in an electronic circuit in a printed board 86, so that an output from an electrometer is obtained. The voltage induced in the electrode 85 is fed back to the electrode 83 and a shield member 81 after the voltage has been measured, so that a stable output from the electrometer can be obtained. |
