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2
The image density sensor checks the density of the sensor pattern i m a g e
once every 10 copy cycles. The CPU receives two voltage values directly
from the sensor: the value for the bare drum (Vsg) and the value for the sen-
sor pattern (Vsp). These two values are then compared to determine
whether or not more toner should be added.
2. Vsp > 1/8 Vsg: Low image density (toner is added)
When the image density is too low, the CPU activates the toner supply clutch
to add a selected amount of toner over the next 10 copy cycles. T h e
amount added depends on the value of Vsp. If Vsp is between 0.5 and 0.6
volt, an amount of toner equivalent to a 30?40 black area copy image is added
If Vsp is between 0.6 and 0.75 volt, the amount becomes
on each cycle.
45%; and if Vsp is 0.75 volt or greater the amount becomes 60%. (These
numbers apply only if Vsg is correctly adjusted to 4 volts.)
sensor can also initiate the toner end condition. If Vsp is 1.2 volts or
The
ID
greater 3 times in a row, the Add Toner indicator turns on.
If Vsg goes below 2.5 volts or Vsp goes above 2.5 volts, the CPU judges
that the ID sensor is malfunctioning. The CPU then stops reading the ID sen-
sor voltage and shifts the copier to 7% fixed toner supply. At the same time
either the Auto ID indicator or the selected manual ID level starts blinking.
Test mode #3 is used to turn on the LED of the sensor manually; when it is
on, VRI02 can be used to adjust the light intensity of the sensor LED.
High image density (no toner is added)
2-22
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