PURPOSE: To prevent the infiltration of a liquid developer, etc., with a simple construction and also eliminate measuring errors caused by the earth potential by providing a shield plate so as to overhang above a measuring window and forming a cut-off part in the part of a supporting plate facing the measuring window.
CONSTITUTION: A base plate 37 is fixed to a supporting plate 51 with screws 52, and between insulating washers 53 on which the base plate 37 is fixed with these screws 52 and the base plate 37, a shield plate 54 formed of, for example, a stainless steel of a thickness about 0.3mm is sandwiched, and it is so arranged that its tip may project, for example, about 1.5W2mm from the tip of a measuring window 39 towards a drum 7. By so doing, the upper side of the measuring window is covered with the shield plate 54 and the infiltration of a liquid developer into an electrometer can be prevented, and measuring errors caused by the earth potential can be eliminated.
SUZUKI KOUJI
NAGASHIMA SUNAO
OGAWA HIROSHI
KURODA KOUKI
NAGAHIRA JIYOUJI
