| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a powder sensor capable of reducing or eliminating erroneous determination compared to the conventional case, when vibration or impact is applied to the sensor. <P>SOLUTION: A powder sensor comprises: an oscillation circuit 10 for applying to a piezoelectric element 5, an output signal Vdrv of at least a resonance frequency Fr of the piezoelectric element 5 or a neighboring frequency thereof via a resistor R1, and also for supplying a high order pulse signal generated during frequency division to a reference signal generation circuit 20 together with the output signal Vdrv for the piezoelectric element 5; the reference signal generation circuit 20 for generating a reference signal Vb of which phase is shifted by a predetermined angle with respect to the output signal Vdrv for the piezoelectric element 5, by logical operation using the inputted signals; a filter circuit 30 to which a terminal voltage Vp of the piezoelectric element 5 is inputted and which outputs a post-filtering signal Vf, where a pass band of the filter circuit 30 includes the resonance frequency of the piezoelectric element 5; and a phase comparison and determination circuit 40 for comparing phases of the reference signal Vb and the post-filtering signal Vf and determining presence or absence of toner in a toner box on the basis of a comparison result. <P>COPYRIGHT: (C)2013,JPO&INPIT |
