Fuji Electric Co., Ltd.

Takeo Kada

Masaru Kohno

Yukio Nakagawa

Gunzi Okawara

Yukia Nakagawa

By detecting the instant of a selected zero-crossing of a received ultrasonic signal rather than relying on the instant the amplitude of that received signal exceeds a predetermined reference amplitude in excess of zero, a transit-time measuring instrument can be realized which is free from the measurement errors normally arising from acoustic signal attenuation in the medium through which it passes.

Ultrasonic measuring instrument

In an ultrasonic fluid flow rate measuring apparatus of the type having a pair of electro-acoustical transducers disposed in respective up-stream and down-stream positions relative a fluid flow and the flow rate is obtained from the difference between the oscillation frequencies of first and second oscillation circuits, the present invention includes an abnormality monitoring circuit responsive to a signal H corresponding to the output of the receiving transducer for providing an output signal W when the signal H exceeds an abnormality monitoring voltage E.sub.1, a trigger circuit for providing an output signal Z to a time difference detection circuit when the signal H exceeds a set voltage E.sub.3 and for providing in response to a signal F an output signal Z to the time difference detection circuit when the signal H exceeds a set voltage E.sub.30, and a mistrigger detection circuit for providing the output signal F when the output signal W is present and when a signal R from the time difference circuit exceeds a set voltage E.sub.61. The present invention further includes a delay compensation circuit for delaying by a predetermined period of time the providing of an output signal from a counter to a delay element, the predetermined period of time being set in accordance with the output signal F of the mistrigger detection circuit.

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Kawasaki, Japan

Takeo Kada