| 摘要 |
<p>PURPOSE:To detect an approaching substance securely and directionally with a simple constitution and to prevent the titled device from the influence of disturbance and misalarm by detecting the substance in accordance with the changes of frequency signals which are based upon the change of stray capacity between sensors and the substance. CONSTITUTION:When the substance approaches the sensors 11, 12, the stray capacity is increased and the level of the attenuation of frequency signals of corresponding networks 31, 32 are increased. The level of the attenuation is changed in accordance with the approaching distance. The attenuated output signals are removed at their noises and sent to voltage variation detecting circuits 61, 62 as DC voltage signals. When the voltage drop is reduced less than a set reference value, the circuits 61, 62 detects the approaching state of the substance and outputs the detected result to an AND circuit 7. The circuit 7 regards that the substance is in the approaching state within a fixed range under the condition that the detecting outputs are in the high level respectively and outputs an alarm signal to an alarm device 10 through a driver 8. Detecting that one sensor detects the substance with a time difference after the other sensor has detected the substance, an alarm releasing circuit 13 releases the alarm.</p> |
