Sensor Control Mode - Gestetner B070 Service Manual

DEVELOPMENT

Sensor Control Mode

In sensor control mode, the machine varies toner supply for each copy to maintain
the correct proportion of toner in the developer and to account for changes in drum
reflectivity over time. The adjustment depends on two factors.
• Amount of toner needed to print the page (based on the black pixel amount for
the page).
• Readings from the TD sensor and ID sensor.
Sensor control mode has two phases, called 'ID sensor control' and 'TD sensor
control'. In ID sensor control, V
check determines the GAIN factor in the toner supply calculation (see later in this
section). In TD sensor control mode, GAIN depends on the current TD sensor
output also (V – V
T
The phase that is used depends on the number of copies since the start of the job.
See the table below for details.
Number of copies in the job
10 or fewer
More than 10
Vref Decision
When new developer is installed, TD sensor initial setting must be done using
SP2801. This sets the sensor output to 2.5 ±0.1V. This value is used as the TD
sensor reference voltage (V
sensor is calculated from the ID sensor output (every time the ID sensor pattern is
read) and the current TD sensor reading (Vt).
If the sensor output cannot be adjusted to within the standard, SC341 or SC342 is
logged and the toner density control is set to the pixel count control.
V and V Detection
SP
SG
The ID sensor detects the following voltages.
• V : The ID sensor output when checking the drum surface
SG
• V
: The ID sensor output when checking the ID sensor pattern
SP
In this way, the reflectivity of both the drum and the pattern on the drum are
checked.
The ID sensor pattern is made on the drum with the charge corona and laser diode.
B070/B071
CÓPIA NÃO CONTROLADA
/V
SP SG
is used).
REF
Copy no.
1 to 10
From 11
). Thereafter, a new reference value for the TD
REF
CÓPIA NÃO CONTROLADA
from the most recent ID sensor pattern
Control method
ID Sensor Control
TD Sensor Control
6-80 SM