| 摘要 |
PURPOSE:To obtain a DC output corresponding to a fluctuation of a toner concentration by varying an output frequency of an oscillating circuit in accordance with the fluctuation of the toner concentration and giving this output frequency to a phase locked loop type circuit. CONSTITUTION:When a toner concentration in a copying machine is fluctuated by following up consumption, a detection signal whose frequency is varied in accordance with a fluctuation portion of the toner concentration is outputted from an oscillating circuit 3 containing a detection coil 1. The detection signal from the oscillating circuit 3 is applied to a PLL. In the PLL, a phase detector 4 compares phases (frequencies) of the detection signal of the oscillating circuit 3 and an output signal of a voltage control oscillator 6. The voltage control oscillator 6 is brought to feedback control through a loop filter 9 so that its output signal is synchronized with the detection signal of the oscillating circuit 3 in the phase detector 4. Accordingly, a DC signal corresponding to the fluctuation portion of the toner concentration in the copying machine is outputted from the loop filter 9. |
