ULTRASONIC FLOWMETER

PROBLEM TO BE SOLVED: To provide a correlation type ultrasonic flowmeter in which a noise mixed into a signal waveform from an ultrasonic receiver is effectively removed to enhance measuring precision. SOLUTION: In this ultrasonic flowmeter 10 for computing a correlation value between signal waveforms output from ultrasonic transceivers 18, 22, 20, 24 arranged an upstream and a downstream of a conduit 100 by a correlation value arithmetic processing unit 36 to compute a flow velocity of a fluid flowing in the conduit 100 based on a time lag between the wave forms in the both, a current meter 36 for measuring a flow velocity fluctuation frequency of the fluid flowing in the conduit 100 is arranged in an upstream side of the upstream ultrasonic transceivers in the conduit 100, and band-pass filters 30, 32 are provided to remove the noise from the signal waveform output to the arithmetic processing unit 36 based on a measured value by the current meter 36.