| 摘要 |
PURPOSE:To make always the true AE alone measurable irrespectively of the degrees of background noise by changing threshold value in correspondence to the fluctuations in environmental noise levels. CONSTITUTION:After the output signal of an AE sensor 1 is amplified 2, it is sent to a threshold value setter 3 and a threshold value changing device 10. In the device 10, the input signal is converted 5 to DC voltage which is compared 6 with the reference voltage corresponding to the noise level under AE measuring conditions from a generator 8. The signal for only the increased portion of the input signal is applied to a servomotor 7, thereby changing the set value of the setter 3. |
