| 摘要 |
PURPOSE: To prevent the occurrence of an error caused by the change of the traveling time of ultrasonic waves by adjusting the delay of a time gate by impressing the output signal of an envelope modulator upon a threshold comparator, the output of which is connected to a gate circuit, and a maximum value detector. CONSTITUTION: The ultrasonic echo of a preamplifier 35 is impressed upon an envelope modulator 38 and an envelope signal is impressed upon a comparator 40. The threshold of the comparator 40 is selected so that the amplitude of the threshold can become slightly larger than that of noise. The output of the comparator 40 is supplied to a gate circuit 43 and forms a starting point of time. An MPU 32 controls the delay time of the circuit 43. The envelope signal is also impressed upon a maximum value detector 44 and the output of the detector 44 indicates the point of time at which the ultrasonic echo becomes the maximum. The output signal of the detector 44 is inspected for the temporal coincidence with the output of the gate circuit 43 at an FF circuit 58. The ultrasonic echo of the amplifier 35 is impressed upon an ECL comparator 49 and the comparator 49 generates an acicular pulse at the zero passing time of the ultrasonic echo. Therefore, a rectangular pulse can be obtained from an AND element 48. |
