3–51OPERATIONS AND TIMINGCOPYRIGHT © 1998 CANON INC. CANON NP6621 REV.0 FEB. 1998 PRINTED IN JAPAN (IMPRIME AU JAPON)2. Toner Level Detection ControlThe level of toner inside the cartridge is monitoredby the antenna sensor circuit.Inside the cartridge is the toner level sensor, andan AC bias is applied to the developing cylinder.The developing cylinder and the toner levelsensor are bonded statistically, and the amount ofstatic charge between the two varies according tothe level of toner inside the cartridge. For thisreason, an AC bias which suits the level of toner isidentified by the toner level sensor and communi-cated to the antenna sensor circuit.The antenna sensor circuit is directly suppliedwith a specific, attenuated AC bias by the compositepower supply for use as a reference signal.The antenna sensor circuit compares the signalfrom the toner level sensor against the referencesignal to find out the level of toner.TonerBladeDeveloping cylinderBlade mount Toner levelsensor Developing assemblyframeAntenna sensor circuitComparator circuitDC controllerPCBTEP*Figure 3-313Download service manual and resetter printer at http://printer1.blogspot.com
