ULTRASONIC VORTEX FLOWMETER

PROBLEM TO BE SOLVED: To provide an ultrasonic vortex flowmeter capable of stably taking accurate measurements of flow rate of gas to be measured. SOLUTION: This ultrasonic vortex flowmeter includes first and second oscillators 31, 32 which cause first and second transmitters 11, 21 to transmit ultrasonic waves of different frequencies so that the ultrasonic waves from the transmitters 11, 21 interfere with each other, and first and second low-pass filters 61, 62 which produce first and second amplitude variation signals B1, B2 by extracting amplitude variations caused by interference from first and second received ultrasonic signals A1, A2 received by first and second receivers 12, 22, the phases of the first and second amplitude variation signals B1, B2 being compared to each other whereby the flow rate of gas to be measured which flows in a tube 2 is calculated on the basis of this phase comparison result. Since the flow rate is measured using the interference between the two ultrasonic waves, accurate flow rate measurements can be stably made without a decrease in measuring accuracy caused by the interference between two ultrasonic waves which occurs in techniques of the prior art.