| 摘要 |
PROBLEM TO BE SOLVED: To enhance detection precision in an ultrasonic propagation time type flow sensor. SOLUTION: In this flow sensor for transmitting and receiving an ultrasonic pulse by ultrasonic echo sounder transceivers 21, 22 arranged in a fluid flow passage, and for detecting an ultrasonic propagation time varied in response to a flow velocity of a fluid to measure a flow rate of the fluid, the noise gate time for turning off a gate circuit 33 to prevent reception of a noise is regulated based on the last measured value of the ultrasonic propagation time measured by an ultrasonic propagation time measuring circuit 36. The gate circuit 33 is thereby turned on all the time in the vicinity before ultrasonic reception timing to receive an ultrasonic wave, even when a composition of the fluid is varied, so as to enhance the flow rate-detecting precision. COPYRIGHT: (C)2003,JPO |
