| 摘要 |
PURPOSE:To permit always exact detection without generating erroneous detection even if a change in the characteristics of a developer arises by providing a function to set the set reference value of a comparator according to a fluctuation of a developing bias or environmental change. CONSTITUTION:The novel reference voltage generating means to change the set reference voltage of the comparator 9 according to the fluctuation of the output voltage of an AC bias power supply 4 and the environmental change in the characteristics of the developer T is provided. This reference voltage generating means is constituted of a hermetic chamber 13, the developer T housed therein, a 1st electrode 14, a 2nd electrode 15, and a signal processing means. The detected signal voltage VDC generated from a current-voltage conversion circuit 8a and the reference voltage VS generated from the reference voltage generating means are compared in the comparator 9, by which the reference voltage can be changed automatically according to the change in the characteristics of the developer T by a change in temp. and humidity. The danger of generating the erroneous detection is, therefore, entirely eliminated. |
