Ricoh B246 SERIES, Manual, Page: 150 / 268

150
150
Drum Potential Sensor
„
Corrects drum
potential sensor
output for
temperature and
humidity
-100/-800
RA102
RA101
Sensor
Output
Charge
on Drum
- 100 V - 800 V
a
b
„
Two-point
calibration
„
Linear relationship
assumed
Service manual, section 6.8.11, Drum Potential Sensor Calibration
ˆ
This corrects the sensor output for effects of temperature and humidity.
ˆ
The development power pack applies two different voltages to the drum shaft.
¾
The voltages applied to the shaft are such that the drum voltage is first –
100V, then –800V.
ˆ
The drum potential sensor outputs are taken for each of these two applied
voltages.
ˆ
From these two readings, the machine can determine the actual drum potential
from sensor output during operation.
¾
The machine assumes a linear relationship. For example, in the diagram, if
the sensor output is ‘a’, the voltage on the drum is determined to be ‘b’.
ˆ
If the gradient of the sensor response is abnormal, auto process control is switched
off, and grid voltage and laser diode power are fixed to the SP mode values. An
error code is logged, but the machine can still be used.
¾
Grid voltage: SP2001 001
¾
LD power: A fixed value in the firmware
¾
Development bias: SP2201 001