| 摘要 |
PURPOSE:To measure flow velocity irrespective of high speed, and also, to measure the sound velocity of a transmitted ultrasonic wave, as well by using a frequency modulated wave as a transmitting wave transmitted from a transducer placed in a liquid, and detecting the difference of frequencies of transmitting/receiving waves. CONSTITUTION:A variable frequency transmitting circuit 3 receives the signals of a clock pulse generating circuit 1 and a timing pulse generating circuit 2 and varies linearly the frequency of an ultrasonic wave transmitted by each transducer P0, P1 in a liquid with respect to the time. A receiving transducer of each transducer P0, P1 receives the ultrasonic wave, and its output signal is sent to a receiving circuit 13 through a transmission/reception switching circuit 11, and sent as receiving outputs H2, H3 to a mixing circuit 14. To the mixing circuit 14, an oscillation frequency deviation quantity E3 being the output of a voltage control oscillator 8 is sent simultaneously, and a difference to the frequency deviation quantity H3 of the receiving output is outputted. From this difference, the flow velocity and the flow direction of the fluid are measured. |
