Patent ID: 8185006

Claim:
A magnetic material detecting device comprising: a magnetic field generating device that is arranged in a two-component developer composed of magnetic carrier and non-magnetic toner, said magnetic field generating device adapted to generate a magnetic field; a signal output device that is arranged in the two-component developer, said signal output device adapted to output a signal depending on a magnetic permeability of the two-component developer due to the magnetic field generated by said magnetic field generating device; an agitating unit adapted to agitate the two-component developer and make the two-component developer flow between said magnetic field generating device and said signal output device; and a detecting unit adapted to detect a proportion of the non-magnetic toner in the two-component developer based on a result of multiple times sampling of the signal outputted from said signal output device after said agitating unit starts to operate; wherein said magnetic field generating device is a drive coil driven by an alternating current signal; wherein said signal output device is an output coil differentially connected to the drive coil; and wherein a transformer unit is composed of the drive coil and the output coil.