| 摘要 |
PROBLEM TO BE SOLVED: To secure sufficiently high measuring accuracy by surely recognizing the first half wave of received waves by forming the first wave of a driving pulse impressed upon an ultrasonic transmitting element in a triangular wave which rises gently and falls steeply. SOLUTION: The first wave P1 of a driving pulse P outputted from a pulse generating circuit is formed in a triangular wave which rises gently P11 and falls steeply P12 . Consequently, the waveform of the received wave which is received by means of and outputted from a receiver becomes that of the received wave W shown in the figure. Namely, the first half wave W1 of the received wave W corresponding to the steeply falling section P12 of the triangular wave P1 becomes such a waveform that becomes the highest at the peak value and descends after the peak value. Accordingly, when, for example, the half wave W1 is not able to be caught, because the reference level for measuring propagating time difference fluctuates and exceeds the peak value of the half wave W1 of the received wave W1 no output is generated. Therefore, the measuring accuracy of an ultrasonic flow rate measuring method can be secured, because the measurement can be discriminated as invalid and the possibility of catching the second half wave W2 and waves after the half wave W2 is eliminated. |
