| 摘要 |
PROBLEM TO BE SOLVED: To provide a capacitive sensor which can improve sensitivity and which can reduce an input conversion noise level. SOLUTION: A guard electrode 4 is disposed between a first electrode 1 and a second electrode 2; an AC electric potential difference between the first electrode 1 and the guard electrode 4 approximately approaches zero so as to be at the same electric potential; and the variation in impedance between the first electrode 1 and the second electrode 2 is detected, by a capacitive sensor detection circuit 64. Thus, by making the apparent electric potential difference between both ends of the parasitic capacitance generated between the first electrode 1 and the guard electrode 4 be small or be at approximately zero, the parasitic capacitance does not function as a capacitor, and the apparent effect on the detection capacitance can be eliminated. Accordingly, only the amount of the variation in the capacitance of the capacitive sensor 10 can be detected by the capacitive sensor detection circuit 64. COPYRIGHT: (C)2005,JPO&NCIPI |
