Ricoh FT4460, Service Manual, Page: 89 / 413

23 May 1989
5.8 TONER DENSITY DETECTION
In this model, the ID sensor normally does not perform a check at the first
copy after power up. Instead, the previous value is stored in memory and the
sensor pattern is checked every 10 copies even if the machine has been
turned off and on several times. However, if the RAM is cleared (SP mode
#99), or a new RAM is initialized, the ID sensor will check the pattern at the
beginning of the 1st copy cycle. From then on it will check every 10 copies.
During the check cycles, the sensor pattern is exposed prior to exposure of
the original. The development bias is fixed for the development of the sensor
pattern, but varies for the different colors (i.e., -260V: black, -320V: green &
blue, -240V: red). The CPU notes the reflectivity of the pattern. If the reflec-
tivity level is too strong, a low toner density condition is indicated and toner is
added to the development unit.
The toner is not added all at once. The CPU energizes the toner supply clutch
to add a selected amount of toner each copy until the next toner detection
cycle.
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