Toonringimeetodi puhul emiteeritakse iga ultraheli impulss kohe pärast eelmise impulsi tuvastamist vedeliku voos ning mõõdetakse impulsi kordumissageduse erinevust kahes suunas, mis on mõõdetava vedelikuvoo kiiruse funktsioon.
By sing around method each pulse is emitted immediately after the detection of the preceding pulse in the stream, and the difference between the pulse repetition frequency in the two directions is measured and is a function of the fluid velocity.
