| 摘要 |
PURPOSE:To enable the application for a proximity switch or the like eliminating effect of external noises with a simple circuit, by triggering a pair of one- shot multivibrators by a trigger generation means simultaneously to detect a time difference between the output thereof by a time difference detection means. CONSTITUTION:A circuit for measuring very small electrostatic capacity is provided with a pair of one-shot multivibrators 11 and 12, to which are respectively connected time constant circuits 13 and 14 different in the time constant and one circuit 14 contains an unknown electrostatic capacity C2. The multivibrators 11 and 12 are triggered simultaneously by a trigger signal from a trigger signal generation circuit 15. Outputs from the multivibrators 11 and 12 are applied to an X-OR gate of an exclusive logic circuit 16 to detect a time difference between the outputs of the multivibrators 11 and 12. An output of the circuit 16 is smoothed with a smoothing circuit 17 and applied to a comparator 19 through a DC amplifier 18 to process the time difference. The results are displayed on an LED 12. Then, the effect of external noises is removed with a simple circuitry to measure the capacity C2. |
