| 摘要 |
PURPOSE:To prevent a measuring error due to the change of magneto-resistance by turning a comparing magnetic circuit for deciding the output of a measuring magnetic circuit detecting the density change of a developer as the change of magnetic permeability to a magnetically closed circuit. CONSTITUTION:A magnetic type toner density measuring device is arranged on the course 7 of toner and carriers in the developing device. Current is made to flow from an AC power supply 5 to coils 31, 32 wound around a measuring core 2 and a comparing core 30 respectively to generate a magnetic field in the arrow beta direction. A coil 6 is reversely wound on the output side of the magnetic circuits 2, 3 to generate a magnetic field in the arrow B and C directions. Current adjusting variable variable resistors 33, 34 are formed on the primary coils 31, 32 respectively and previously adjusted so that the output of the coil 6 becomes zero when the contents of the developer 7 is a proper value. The core 30 of the comparing magnetic circuit is made a closed magnetic line. An output is generated in accordance with the change of magneto-resistance generated by the density change of the developer 7, detected 10 at its phase, and then amplified 12 to feed toner by a driving part 13. Thus, the change of the measuring errors is reduced. |
