METHOD AND DEVICE FOR DETECTING DEVELOPER CONCENTRATION

摘要

PURPOSE:To provide a detecting method and the device thereof which always realize measurement with fixed bulk density 50 as to stably detect developer concentration over a long term. CONSTITUTION:The developer concentration at an accumulation part is not measured by a magnetic permeability sensor 10 merely while developer is cyclically stirred under a state that the developer is accumulated. However, the developer concentration is detected by the sensor 10 under the state that only the developer to be detected by the sensor out of the developer housed in a developing container 1 is magnetically held by a means obtained by arranging a pair of magnets 31 by facing the different poles thereof to each other by interposing the developer concentration detecting area of the sensor 10 in a fixed magnetic field where magnetic force is not changed.