Acoustic current meter

摘要

An acoustic current meter in which two channels have acoustic paths oriented at right angles to each other to measure orthogonal components of a current velocity. Each channel includes two transducers aimed at an acoustic mirror so that the reflected acoustic signal from each transducer impinges upon the opposite transducer. Periodically, a burst of high frequency acoustic energy is simultaneous emitted by each transducer. A current flowing produces a relative phase shift between the received signals representative of the current velocity. The output signal produced by each of the transducers is mixed with a common reference signal to provide two, low frequency, beat frequency signals having a phase difference proportional to the current velocity. Due to the reduction in frequency, the phase shift is expanded in time with respect to the phase shift of the acoustic signals and may be easily measured.