| 摘要 |
PURPOSE:To reduce variance in toner sensor sensitivity gradient by returning the gradient to the former sensitivity gradient by sensitivity resistance after raising the sensitivity gradient. CONSTITUTION:AC driving voltage is impressed to a primary side of a transformer with a differencial connection, and the toner sensor which outputs analog signal Va responding to phase difference between a differencial output of the transformer and a driving voltage is utilized. Then, comparative voltage Va' is generated to the difference between a first reference level V1 and a signal Va by a first calculation amplifier, and voltage Vo in ratio to the difference between a second reference level V2 and a signal Va' is generated by a second calculation amplifier. At this time, values of levels V1 and V2 are selected so that the maximum voltage of the voltage Vo is made below 7V, and the toner concentration is judged by the voltage Vo. Thus, the variance of the sensitivity gradient is made small and the sensitivity gradient can be controlled at a point of superior linearity. |
