| 摘要 |
PURPOSE:To remove the cause of a difference in measuring and to accurately adjust the concentration of a developer when the developer is exchanged by setting the regulating value of the concentration of the developer at a range where the output properties of a concentration sensor are excellent. CONSTITUTION:Set value memory 7a and 7b stores the top/bottom threshold values of the concentration set in advance in the range where the linearity of the permeability- to-output characteristics of the concentration sensor 17a is secured. A deciding part 8a decides whether the value of the toner concentration measured by the sensor 17a is within the ranges of the top/bottom threshold values read out from the memory 7a and 7b, or not, when the developer 10a of a housing part 11a is exchanged. When the measured toner concentration value is within the ranges of the threshold values, as the result of the decision of the deciding part 8a, regulating value memory 190a stores the measured concentration value as a regulating value. When the measured toner concentration is out of the ranges of the top/bottom threshold values, as the result of the decision of the deciding means 8a, an error display part 21 carries out an error display. Thus, the concentration is accurately adjusted by the set regulating value, and when the measured value is out of the ranges of the top/bottom threshold values attaching precision is enhanced and the difference in the measuring is prevented. |
