Canon FY8-13EX-000, NP6218 service manual B. Controlling the Toner Level Detection, 4-23

CHAPTER 4 IMAGE FORMATION SYSTEM

B. Controlling the Toner Level Detection

The level of toner inside the cartridge is monitored by the antenna sensor circuit. The toner level sensor is found inside the cartridge, and an AC bias is applied to the

developing cylinder.

The developing cylinder and the toner level sensor are connected by means of static electricity; the volumes of charges between the two vary according to the amount of toner inside the cartridge; as a result, an AC bias that represents the level of the toner is checked by the toner level sensor, and the data is sent to the antenna sensor circuit.

The antenna sensor circuit receives a reference signal from the composite power supply circuit; the reference signal is an AC bias with a specific AC bias that has gone through attenuation.

In the antenna circuit, the signal coming from the toner level sensor and the reference signal are compared to find out the level of toner.

Blade mount	Toner level	Developing assembly
	sensor
		frame

Toner

Blade

Antenna sensor circuit	DC controller
	PCB

Developing cylinder	Comparator circuit
	TEP*

Figure 4-202

COPYRIGHT © 1997 CANON INC. CANON NP6218 REV. 0 MAY 1997 PRINTED IN JAPAN (IMPRIME AU JAPON) 4-23