| 摘要 |
PURPOSE: To obtain an apparatus not responding to environmental and physical restriction by compressing the preliminarily selected part of a developer substance by a magnetic field and forming a signal through a forming means and changing the signal as the function of the concn. of a toner substance. CONSTITUTION: A sensing head 136 is driven by an oscillator 150 and the output from a head 136 is amplified by a amplifying sub-circuit 152. The amplified signal is processed in a pulse form by a signal processing circuit 154 and these pulses are counted by a counter sub-circuit 156. After counting, pulses are converted to signal output having amplitude and frequency by a processing circuit 158. During work, a developer mixture flows by a head 136 and the amplitude and frequency of the signal formed therein change as the function of the magnetic permeability of the developer mixture. This magnetic permeability increases as the toner in a developer reduces and, as a result, both of the frequency and amplitude of signal output are reduced. If standard calibration technique is used, the frequency or amplitude of signal output for an arbitrary operation point can be related to the corresponding toner density. |
