| 摘要 |
PROBLEM TO BE SOLVED: To provide an ultrasonic flow meter to judge an abnormality in transmission and reception of the ultrasonic signal by a simple configuration. SOLUTION: A transmit-receive circuit unit 11 controls ultrasonic transducers 3, 4 to transmit/receive the ultrasonic signals (a plurality of pulses) to/from each other, and the received signal is outputted to a comparator circuit unit 12. The comparator circuit unit 12 outputs 'H' when the voltage of the received signal exceeds the reference voltage. A propagation time measuring circuit unit 13 measures the propagation time of the ultrasonic signal based on the output of the comparator circuit unit 12. A counter circuit 14 achieves the increment of +1 for each 'H' output of the comparator unit 12. An upper rank operation circuit 15 calculates the flow speed and the flow rate of the fluid based on the above propagation time, and when the counted value by the counter circuit 14 is different from a preset reference value, an abnormality in transmission/reception of the ultrasonic signal is judged, and the results of calculation of the flow speed and the flow rate are discarded.
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