| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a powder sensor which has, compared to conventional sensors, less or no chances of making false detection when subjected to vibration or shock. <P>SOLUTION: In a square wave signal generator circuit 14, a power supply voltage Vcc is divided by resistors R<SB POS="POST">H</SB>, R<SB POS="POST">L</SB>with a division ratio of 1:1, for example, to produce a reference voltage Vr which is fed to an inverting input terminal of a comparator 41, and a terminal voltage Vp of a piezoelectric element 5 is offset by an offset circuit 42 to produce a voltage Vb which is fed to a non-inverting input terminal of the comparator 41. The comparator 41 transforms the terminal voltage Vp of the piezoelectric element 5 into a square wave to produce a square wave signal V1 at the output terminal thereof. The offset is applied such that the difference between the DC component of the voltage Vb after offset and the reference voltage Vr is greater than the difference between the DC component of the terminal voltage Vp of the piezoelectric element 5 and the reference voltage Vr. <P>COPYRIGHT: (C)2013,JPO&INPIT |
