| 摘要 |
PURPOSE:To prevent the entry of a toner and the like into the inside of a probe, by a method wherein an electrode plate is placed through the medium of an insulating plate at the circumference of an aperture in a probe, and a given potential is applied to the electrode plate. CONSTITUTION:An insulating plate 15, whose diameter is larger than that of an aprature 13, is placed on a surface of a casing 11 of a probe consisting of a conductor, and an electrode plate 16, whose diameter is larger than that of the insulating plate 15, is further located on the insulating plate 15. A potential, which has a reverse polarity to that of a toner potential, is applied to the electrode plate 16 by means of a D.C. power source 17 or 18, and with this a toner, which is going to enter through the aperture 13, is captured, and is prevented from entering into the inside. The electrode plate 16 is isolated from the casing 11 through the medium of the insulating plate 15, and thereby an influence is not exercised upon an potential of a detecting electrode 12 located at the inside. This completely prevents the entry of electrified dust, such as toner, into the inside of the potential probe, and permits the highly precise measurement of the potential. |
