JPS54107362A - Karman vortex current meter - Google Patents

Abstract

PURPOSE: To make detection of vortex generating frequencies easy even at low velocities by providing temperature differences, etc. between the measuring fluids on both sides of a vortex generating column on the upstream side of the vortex generating column in measuring the velocities of flow by detecting the number of Karman vortexes generating on the lower stream of the vortex generating column with ultrasonic waves.

CONSTITUTION: When fluid flows in a conduit 1, a vortex generating column 2 generates Karman vortexes 3, 4. An ultrasonic wave transmitter 5, driven by an oscillator 6, transmits ultrasonic waves to a receiver 7. Then, the ultrasonic waves are modulated by the Karman vortexes and the modulated ultrasonic waves are received in the receiver 7. In a reception unit 8, the generation frequencies of the Karman vortexes are detected. When the velocity of flow of the fluid is low, the Karman vortexes are weak and give lower degrees of modulation and therefore a temperature difference is given between the clockwise Karman vortexes and the counterclockwise Karman vortexes by heating the fluid of the B side with an electric heater 10. As a result, the ultrasonic waves propagaging become those which have been applied with the modulation by the Karman vortexes and the modulation owing to the differences in the rate of propagation by the temperature differences between the Karman vortexes 3 and 4, thus it becomes possible to readily detect the Karman vortexes of low velocity of flow.

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