JPS6478115A - Vortex flowmeter - Google Patents

Abstract

PURPOSE:To execute the measurement with high sensitivity by a simple constitution by providing at least two pairs of ultrasonic transmitters and ultrasonic receivers, and providing them on a position where they are subjected to phase modulation by a Karman vortex, and a position where they are not influenced substantially thereby, respectively. CONSTITUTION:On a position for traversing a fluid of the upstream of a vortex generating body 7, an ultrasonic transmitter 9a and its receiver 9b are provided, and in the same way, on a position for traversing a fluid of the downstream of the vortex generating body 7, an ultrasonic transmitter 10a and its receiver 10b are provided. When an ultrasonic wave which has been transmitted from the transmitter 10a encounters a Karman vortex, its phase is varied. An ultrasonic wave which has been transmitted from the transmitter 9a is not influenced by the vortex. Also, an external factor such as a temperature variation, etc., exerts the same influence on the phase of two ultrasonic waves. Accordingly, ultrasonic signals which have been received by the receivers 9b, 10b are amplified 11, 13, and thereafter, can cancel a variation of the phase, caused by the external factor in a phase comparator 13, a relative phase difference of two ultrasonic waves always becomes constant, and an operating point of the comparator 12 can always be made constant.