초록 ▼

A toner concentration sensor senses the concentration of toner in the toner system of an electro-photographic printer or copier. A novel circuit improves the toner concentration sensor. The novel circuit is composed of a resonant circuit, a frequency source, and a logic circuit. The resonant circuit

A toner concentration sensor senses the concentration of toner in the toner system of an electro-photographic printer or copier. A novel circuit improves the toner concentration sensor. The novel circuit is composed of a resonant circuit, a frequency source, and a logic circuit. The resonant circuit is tuned to a selected frequency and has an inductor which creates a field into which the toner system is introduced. A frequency source excites the resonant circuit. A logic circuit receives a signal from the frequency source and an output from the resonant circuit. The logic circuit output is a signal representative of the phase shift between the signal from the frequency source and the output of the resonant circuit. The phase shift is representative of the inductance of the inductor in the presence of said toner system. The measurement of the inductance is representative of the concentration of toner in said toner system.

대표청구항 ▼

An apparatus for monitoring the concentration of toner in a toner system, said apparatus comprising: means for holding a supply of said toner system, said toner system including a mixture of toner particles and ferromagnetic carrier beads; a resonant circuit tuned to a fixed predetermined frequency,

An apparatus for monitoring the concentration of toner in a toner system, said apparatus comprising: means for holding a supply of said toner system, said toner system including a mixture of toner particles and ferromagnetic carrier beads; a resonant circuit tuned to a fixed predetermined frequency, said resonant circuit including a sensor coil surrounding a portion of said holding means; means for exciting said resonant circuit with a first signal, said first signal\s frequency being said fixed predetermined frequency; and logic circuit means, responsive to a second signal from said exciting means, said second signal\s frequency also being said fixed predetermined frequency, said logic circuit means further being responsive to an output from said resonant circuit, said logic circuit means for generating at its output a signal representative of a phase shift between said second signal and the output from said resonant circuit, the amount of said phase shift indicative of the actual concentration of the toner in said toner system.