| 摘要 |
PROBLEM TO BE SOLVED: To automate adjustment by smoothening a pulse train in which high and low levels are repeated, with a low-area-pass filter and making a sensitivity adjusting voltage inputted to a toner concentration sensor variable. SOLUTION: The sensitivity adjusting voltage outputted from the low-area- pass filter 5 is converted into a digital signal by an A/D conversion circuit 7, to be fetched in a CPU 6, so that the feedback control of the sensitivity adjusting voltage is executed to make a voltage for showing the output value of the A/D conversion circuit 7 coincident with a voltage recorded in a nonvolatile memory, at the time of initializing the sensitivity adjusting voltage. The cycle of the pulse train inputted to the low-area-pass filter 5 is defined as T and the ratio of a H-level time per cycle of the pulse train 10 is defined as (x) and when x=0 is obtained, the pulse train is always at the L-level, so that the sensitivity adjusting voltage becomes 0V. Further, when x=1 is obtained, the pulse train adjusting voltage is always at the H-level, so that the sensitivity adjusting voltage becomes 0V. Further, when 0<x<1 is obtained, the voltage level of the pulse train is timewisely averaged by the low-area-pass filter 5 and the sensitivity adjusting voltage is proportioned to the ratio (x). |
