| 摘要 |
PROBLEM TO BE SOLVED: To solve the problem that a charging voltage is limited by the power- supply voltage of a detector although the detection sensitivity of a capacitance can be increased by increasing the charging voltage of a detection electrode, or by reducing a reference capacitance in the case of a voltage charging method, and that the influence of a disturbance noise or a noise in the operation of a circuit is increased so as to worsen an S/N ratio when the reference capacitance is reduced. SOLUTION: Under the control of a switching operation by a timing controller 16, a switch SA is first turned on at a sensor cell 100-k. The potential of the detection electrode is set to a reference potential (a GND level in this example). The switch SA is then turned off. A switch SB is turned on and the electric charge of the sensor cell 100-k is taken into the reference capacitance Cf1. The above procedure is repeatedly performed. The number of times of the operation is increased, the detection sensitivity is increased. A noise component is reduced by an averaging (integration) processing operation, and only a signal component is taken out. |
