JPS5582925A - Ultrasonic flow meter - Google Patents

Abstract

PURPOSE:To stop measurement when an abnormality such as the invasion of extraneous substance or the vibration of a pipe takes place, by utilizing ultrasonic waves which are propagated through the wall of the pipe, reflected on its inside surface and come back into receivers. CONSTITUTION:Selection circuits 14c, 14d, which extract only the outputs of receivers 12a, 12b corresponding to ultrasonic waves VN1, VN2 propagated through the wall of a pipe and reflected on its inside surface, and amplitude detection circuits 15c, 15d, which generate output signals proportional to the amplitudes of the outputs of the selection circuits, are added. Fluctuation detection circuits 16a, 16b made of differentiation circuits or the like detect the fluctuation in the output signals of the receivers 12a, 12b. When the fluctuation exceeds a prescribed level, an output signal is supplied to an OR circuit 17. When at least one input signal is applied to the OR circuit, it generates an output signal to keep a comparison circuit 7 out of operation. As a result, a flow rate is not measured when an error is likely to take place. Therefore, the accuracy of the measurement is raised.