| 摘要 |
Capacitance measurement apparatus that enhances the sensitivity and accuracy of capacitive transducers, proximity sensors, and touchless switches. Each of two capacitors (C 1 , C 2 ) under measurement has one end connected to ground and is kept at substantially the same voltage potential by operational amplifier (A 1 ) or amplifiers (A 0 , A 1 ) using negative feedback. The apparatus is driven by a periodic e.g. sinusoidal signal source (G 1 ) or sources (G 1 , G 2 ) and includes a difference amplifier (A 2 ) operative to produce an electrical signal having a linear relationship with a specified arithmetic function of the capacitances of the two capacitors (C 1 , C 2 ). A touchless switch is implemented using the capacitance measurement apparatus. The touchless switch includes two sensor electrodes (E 1 , E 2 ) that correspond to the two capacitors (C 1 , C 2 ) under measurement and in one embodiment has a front surface in the form of a container.
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