Acoustic flow velocity measuring device - uses difference measurement between velocity of sound with and against current

摘要

The flow velocity is measured by measuring the difference between velocity of sound with and against the current. Both measurements are made over the same test distance by the same measurement circuit. Sound velocity is measured by the sing-around method, and the difference frequency is counted by a reversible counter; or the sound velocity is calculated by an electronic calculator from the time one or a certain number of sound pulses take to travel over the test distance; or several test sections are operated in multiplex by a measurement circuit. In all cases a single test length and measuring circuit is used thereby keeping costs down.