| 摘要 |
The method involves producing acoustic signals in a measurement chamber (54) for a short-time, by a piezoceramic disk (68). Change in resonance characteristics of the measurement chamber is measured for delivery of error signals, when the resonance characteristics are measurably changed. A number of oscillations of the acoustic signals are measured after completion of the production of the acoustic signals. The number of oscillations is compared with a preset value. Decaying oscillations of the piezoceramic disk are counted. An independent claim is also included for an alarm device comprising a measurement chamber with an opening. |
