FIELD: measuring facilities and methods. SUBSTANCE: according to proposed invention time of passing of two acoustic signals transmitted in opposite directions between two points of fluid medium flow is measured with simultaneously measuring corresponding phase shifts of acoustic signals appearing in each signal. Each received signal is sampled and converted into digital form, and corresponding phase shift of acoustic signal is found by synchronous detection. In course of sequential interactions (approximations) for each interaction such program-controlled phase shift is determined, coupled with value of phase shift of acoustic signal and found by synchronous detection in process of preceding interaction, at which result of step of synchronous detection of current iteration is as close to zero as possible, and phase shift of acoustic signal is approximately equal to final program-controlled phase shift. EFFECT: reduced consumption of energy owing to reduction of scope of calculations. 24 cl, 13 dwg
