Ricoh FT6645 Manual page 30

23 April 1993
1.3 LATENT IMAGE CONTROL
1.3.1 Drum Potential Sensor Calibration
RA601
-100 V
-800 V
RA602
Main PCB
The drum potential sensor [A] is located just above the development unit. The
sensor has a detector which detects the strength of the electric field from the
electric potential on the drum. The output of the sensor depends on the
strength of the electric field.
Since the output of the sensor is affected by environmental conditions, such
as temperature and humidity, the sensor output is calibrated during process
control data initial setting.
The High Voltage Control PCB [B] has two relay contacts. Usually RA602
grounds the drum. However, during the initial setting, the main PCB turns
RA601 on and RA602 off and applies the voltage to the drum shaft.
By measuring the output of the drum potential sensor when –100 V and –800
V are applied to the drum, the sensor output is calibrated automatically.
(The machine recognizes the relationship between actual drum potential and
the potential sensor output.)
[A]
Drum
[B]
2-5
PROCESS CONTROL
Case
Sensor
Output
Amp.