| 摘要 |
PURPOSE:To decrease the detecting error due to the dirt on a detecting portion and increase a detecting accuracy by detecting the voltage affected only by the capacity of a capacitor for detecting a position, said capacity being changed by the displacement of a movable object. CONSTITUTION:The portion 15 to be detected of a movable object 14 withdrawably intervenes between the electrodes 12 and 13 of a capacitor 1 for detecting a position and the capacitor C1 of the capacitor 1 is changed. A reference capacitor 2 with a capacity C2 is connected to the capacitor 1 in series. Sampling signals S1 from a sampling signal generating circuit 7 are turned to rectangular pulses through a one-shot circuit 10 and operate transistors Trs 4 and 5 in a switching circuit 3. When the Tr 4 is turned on, the capacitors 1 and 2 are supplied with a DC voltage V from a power supply 6 to be charged. The signals S1 are supplied also to a sample hold circuit 9 and, in synchronism with the supply of the signals S1, the circuit 9 holds a voltage value S3 corresponding to the voltage V0 applied across the capacitor 1. An operation wherein the capacity C1 of the capacitor 1 is determined (11) from the voltage value S3, known values V and C2 is prepared and the positions of the object 14 are sequentially detected.
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