ULTRASONIC METHOD FOR MEASURING FLOW VELOCITY

摘要

PROBLEM TO BE SOLVED: To provide an economical ultrasonic method for measuring flow velocities in which a propagation time of ultrasonic waves can be accurately obtained from a small flow rate to a large flow rate, and power consumption can be suppressed low. SOLUTION: Ultrasonic vibrators 2 and 3 are set respectively to the upstream side and the downside of a measurement fluid flowing in an ultrasonic flow velocity measurement pipe 1. Ultrasonic waves are transmitted mutually from the ultrasonic vibrators 2 and 3, and at the same time, the transmitted ultrasonic waves are mutually received. Propagation timesτ,τ' of the ultrasonic waves are obtained with the utilization of a clock wave L outputted simultaneously with the transmission of the ultrasonic waves. A flow velocity v is measured on the basis of a difference of the propagation times of the ultrasonic waves. A period T0 of the clock waves L is changed over in accordance with a flow rate Q calculated on the basis of the flow velocity v.