Led Light Density Ctd (Adc) Control Of Sensor - Xerox Phaser 6250 Service Manual

If toner density is too great (excess toner) and 16 dispense counts are required to
subtract this amount, the adjustment is accomplished by subtracting 2 counts from the
calculated PCDC count over each of the subsequent 8 prints. If the excess amount
cannot be subtracted in 8 print cycles, it is subtracted in the ninth and subsequent
prints.
Total dispense counts
Correction amount by ADC +16
Dispense counts by PCDC
Correction amount by ADC -8
Total dispense counts
High-Area Coverage Mode
Continuous printing of an image with density exceeding the toner dispense capability
causes the toner density in the developer to be lowered below the target toner density.
The high area coverage mode delays feeding of the next page, and dispenses toner
during this time so that the toner density time reaches the specified value during
continuous printing.
Admix Mode
If the high area coverage mode can not deal with the reduction of toner density in the
developer or if the machine is moved to an environment with a different humidity
level, the reference value for the toner density will change. This causes a large
discrepancy between the measured values from the CTD sensor and the referenced
value for the toner density.
Admix mode dispenses the toner immediately to prevent low-toner density. If the
patch density result measured by the CTD Sensor is lower than the reference value
from the toner density control, then the admix mode is initiated.

LED Light Density CTD (ADC) Control of Sensor

The CTD (ADC) sensor is a reflective sensor that emits light from an LED in the
sensor and detects the reflected light from the transfer roller. For exact density
measurement, the sensor output value (reflected light density) must be the specified
value when no toner is put on the Transfer Roller. The reflected light density varies
2-8
4 5 3 4
Even allotment in first 8 prints
2 3 1 2
1 2 0 1
Phaser 6250 Color Laser Printer Service Manual
2 2 3 4
0 0 1 2
0 0 0 0
3 2
3 2
2 2
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