Method of measuring the propagation time of a sound signal in a fluid by means of a zero-crossing of said sound signal

摘要

Measuring the propagation time of a sound signal between two spaced-apart transducers disposed in a fluid flow involves determining the zero-crossing of the signal. Each received sound signal is sampled and digitized, then for each period of the sampled and digitized signal the maximum amplitudes P- and P+ of the two lobes of the period under examination are determined. The ratio of the amplitudes are compared to an ideal amplitude ratio between the maximum amplitudes Pi- and Pi+ of two lobes of a first ideal characteristic period. The first zero-crossing of the characteristic oscillations of the signal is determined. And, as a function of the result of the comparison relative to a threshold value Gs, the period under examination is accepted or ignored as a characteristic period. The zero-crossing thereof is determined or not determined between the two lobes of the characteristic period.