| 摘要 |
PURPOSE:To enable abnormalities such as cracking of a glass and falling-off from the glass surface to be detected by giving vibration pulses to the glass surface and then comparing a data of specified frequency constituents which are taken out of reflection pulses with a previous data. CONSTITUTION:A voltage of a specified level is given to a piezoelectric element 1a from an oscillator 1b through a switch 1c, voltage signal from the element 1a which is driven by reflection pulses from a glass surface is output to a filter amplification circuit 2 through the switch 1c, only a specified frequency band, for example, only electrical signal around 200 kHz which can be transmitted easily on the glass surface is taken out as a sampling data by a filter circuit 2a and is amplified to a specified level. Then, it is fed to a comparator 4 and is compared with a data of reflection pulses which are memorized 3 when the glass is normal. If the difference exceeds a specified level, abnormal signal is sent from an output circuit 5 to a receiver side, thus enabling abnormalities such as cracking of the glass which prevents sound from being generated and falling-off of a detector itself form the glass surface due to aging of an adhesive to be detected effectively. |
