| 摘要 |
PURPOSE:To detect exactly a rise time of a receiving wave even in case of a medium in which a driving excess pulsating wave and the receiving wave are superposed, and to measure a flow rate with a high accuracy, by measuring an ultrasonic propagation time basing on a rise time of an ultrasonic waveform. CONSTITUTION:Envelope sampling information S1, S2 and sampling time information S3 obtained from ultrasonic transmitting and receiving circuits 1, 2 are stored successively in input control circuits 4, 5 and 6, respectively, by a control pulse signal S300. Subsequently, a calculating circuit 7 receives each sampling time information S3 from a latching circuit of the input control circuit 6, and also receives the envelope sampling information S1, S2 at each time from latching circuits of the input control circuit 4, 5, respectively. An m-order function fm is determined basing on said information, each ultrasonic propagation time T1, T2 is derived by calculating numerically the time when this m-order function fm passes through a zero point Z, and a flow velocity of a fluid and its flow rate are calculated, and outputted so as to be displayed on a display device 8. |
