| 摘要 |
PURPOSE:To get rid of influence of an induced noise, by supplying a capacitive sensor to the other input terminal of a comparator to which the capacitive sensor is connected through a low-pass filter. CONSTITUTION:A moving electrode 1c of a capacitive sensor 1 is connected to a + input terminal of a comparator 4, also is connected to a - input terminal of a low-pass filter 20 through the low-pass filter 20, and accordingly, reference voltage Va applied to a - input terminal of the comparator 4 is varied by synchronizing with a noise signal induced to the moving electrode 1c, and oscillation frequency of a self-energizing oscillating circuit containing the comparator 4 is not influenced by a noise signal. |
