초록 ▼

A method for measuring a fluid flow rate between two points of a fluid flow according to which a measurement of the respective propagation times of two acoustic signals transmitted in opposite directions is combined with a measurement of acoustic phase shifts respectively induced in each signal. Eac

A method for measuring a fluid flow rate between two points of a fluid flow according to which a measurement of the respective propagation times of two acoustic signals transmitted in opposite directions is combined with a measurement of acoustic phase shifts respectively induced in each signal. Each received signal is sampled and digitized and the corresponding acoustic phase shift is determined by synchronous detection. During successive iterations, a programmable phase shift dependent on the value of the acoustic phase shift obtained by synchronous detection in the previous iteration is determined for each iteration, so that the result of the synchronous detection step in the current iteration is as close as possible to zero, and the acoustic phase shift is therefore substantially the same as the last programmable phase shift.

대표청구항 ▼

[ What is claimed is:] [1.] Method for measuring a fluid flow rate between two points spaced in the direction of a flow of a fluid whereby the flow rate is obtained by combining a measurement of the respective propagation times of each of two acoustic signals transmitted between the two points in op

[ What is claimed is:] [1.] Method for measuring a fluid flow rate between two points spaced in the direction of a flow of a fluid whereby the flow rate is obtained by combining a measurement of the respective propagation times of each of two acoustic signals transmitted between the two points in opposing directions with a measurement of acoustic phase shifts respectively induced in each acoustic signal by the propagation of each of said acoustic signals in the flow, the measurement of the acoustic phase shift induced in each acoustic signal consisting of sampling said acoustic signal received at a sampling frequency, of digitalizing the sampled signal and of determining by synchronous detection the acoustic phase shift as being the phase difference between the phase of the sampled signal and the phase of a reference signal, characterized in that the method starts by successive iterations on various acoustic signals successively transmitted in the same direction of propagation by introducing during an iteration of order n+1 in one of said acoustic signals between the signal transmission stage and the synchronous detection stage at least one programmable phase shift .tau.p(n) tied to the value of the acoustic phase shift .phi.(n)+.phi.ref determined by synchronous detection carried out at the time of the preceding iteration of order n on the signal previously transmitted and which is equal to firstly the sum of the phase difference .phi.err(n) between the phase of the signal sampled at the time of the preceding iteration of order n and the phase of the reference signal, and secondly of the programmable phase shift introduced during the iteration of order n, 2.pi.Fac.tau.p(n-1) where Fac represents the frequency of the acoustic signal and .tau.p(n-1) represents a programmable delay determined at the iteration of order n-1 so that the synchronous detection stage of the iteration of order n+1 determines a phase difference .phi.err(n+1) between the phase of the sampled signal at the time of the current iteration and the phase difference which is as close as possible to zero, the acoustic phase shift .phi.(n+1)+.phi.ref thus being approximately equal to the programmable phase shift introduced at the time of the iteration of order n+1, 2.pi.Fac.tau.p(n).