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2. PROCESS CONTROL
2.1 LATENT IMAGE CONTROL
2.1.1 DRUM POTENTIAL SENSOR CALIBRATION
[A]
Main Board
The drum potential sensor [A] output is calibrated during the process control
self check.
The High Voltage Supply Board - B [B] has two relay contacts. Usually RA
#1 grounds the drum. However, during the self check, the main CPU turns
RA #2 on and RA #1 off and applies the test voltage to the drum shaft [C]. In
this condition, the drum is isolated from the ground (floating).
By measuring the output of the drum potential sensor when –300 V (V
–600 V (V
) are applied to the drum, the sensor output is calibrated
600
automatically. (The machine can now determine the actual drum potential
from the potential sensor output.) Using -300 and -600 V results in a more
accurate calibration of the sensor, since the voltage applied to the supply
board is much closer to the actual value, which is –450 V for V
(Development bias) during the process control self check.
SM
[C]
RA#1 and RA #2 are contained in RL1
RA #2
on the High Voltage Supply Board – B.
– 3 0 0 V
– 6 0 0 V
RA #1
Sensor Output
V600 (V
)
2
V300 (V
)
1
– 3 0 0
2-5
[B]
– 6 0 0
Actual Voltage
B
A172/A199
) or
300
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