| 摘要 |
PURPOSE:To accomplish the stable and accurate measurement of toner residual without receiving the effect of temperature and an external noise by detecting the size equal to a signal induced in an antenna electrode provided close to a developing roller and detecting the toner residual. CONSTITUTION:As to the signal induced in the antenna electrode 7, only a signal depending on the toner residual where the frequency in a desired band centering around the frequency f0 of an AC bias signal, namely overshoot external noise of the AC bias signal, is cut is made to pass with the aid of the band pass filter function of an AC amplifier 11 and it is amplified, rectified in a rectification circuit 12 and outputting from a terminal 13. The output signal becomes a signal expressing the toner residual and the accurate and stable detection of the toner residual can be performed without receiving the effect of the external noise and the variation of temperature. Thus, the stable and accurate detection of the toner residual which hardly receives the effect of the variation of temperature and the external noise can be obtained. |
