| 摘要 |
PURPOSE:To obtain always stable trigger point of signal, even if the measured fluid is in bad condition and the attenuation of signal is rapid, by selecting the polarity of the reception signal at the signal polarity selection section according to the output of the comparator. CONSTITUTION:After the signal from the reception signal input terminal 21 is amplified at the amplifier 22, it is fed to the signal polarity selection section 23, and the output signal 26 having the polarity selected at the polarity selection signal 27 is obtained. Further, the signal 26 is compared with the reference voltage 25 (polarity selection level) at the comparator 24, and if the value is less than the polarity selection level, the signal 27 is fed to the selection section 23 to select the polarity of the signal 26 and it is balanced when stable time detection point is obtained. |
