Toner quantity measuring technique in an electrophotographic printer

摘要

A printer is provided with a transmit electrode and a receive electrode with a dry-toner cartridge located therebetween. The transmit and receive electrodes act as two plates of a capacitor, with the toner within the toner cartridge making up a portion of the dielectric between the two capacitor plates. An oscillating transmit signal is then applied to the transmit electrode, and a signal corresponding to the capacitance between the opposing electrodes is detected. The changing capacitance due to the changing toner quantity causes a change in the received signal. The value of the received signal is then converted into the quantity of toner residing between the opposing electrodes, and this quantity is displayed to the user. Arrangements of transmit and receive electrodes may be employed within the printer to not only sense the overall quantity of toner but the distribution of toner within the toner cartridge.