| 摘要 |
PURPOSE:To obtain an ultrasonic current meter having good performance, by using a continuous ultrasonic wave propagating as an ultrasonic wave which is a standing wave in the section of a pipe, and a progressive wave in the axial direction of the pipe, in the pipe. CONSTITUTION:A sine signal (a) generated by a continuous oscillator 1 is converted to an ultrasonic wave by an ultrasonic transmitter T, a part of which is converted to a square wave C (reference wave) by a converting circuit 2. Also, the ultrasonic wave which propagates in a fluid is converted again to an electric signal (b) by an ultrasonic receiver R, is amplified by an amplifier 3, and is converted to a square wave (d) (receiving wave) by a converting circuit 4. A phase difference psi of the reference wave and the receiving wave is detected by a phase difference detecting circuit 5. In case of a flow velocity v=0, by adjusting so that an output (g) becomes zero, a phase difference psi being proportional to a difference DELTAt of a propagation time in case of the flow velocity v=not equal to 0 and a propagation time in case of the flow velocity v=0 appears as the output (g) of a differential amplifying circuit. Since the degree of freedom in the fitting method of the ultrasonic transmitter T and the receiver R is large, it is also possible to measure a flow velocity in a slender pipe or in a complicated pipe, and it is executed by analog processing, therefore, the inaccuracy of rise of a pulse is canceled, and also the circuit is obtained easily and at a low cost. |
