Flow measurement by amplitude difference

Abstract

A measuring method, implemented in a meter (1) comprising a conduit (4) in which a fluid circulates and an ultrasonic measuring device (6) comprising an upstream transducer (7a) and a downstream transducer (7b), the measuring method comprising the steps of: - applying an electrical excitation signal (Se) to the terminals of the upstream transducer, and acquiring a downstream electrical signal produced by the downstream transducer; - applying the electrical excitation signal to the terminals of the downstream transducer, and acquiring an upstream electrical signal produced by the upstream transducer; - evaluating a flow rate of the fluid in the conduit as a function of a first value representative of a difference between an amplitude of the upstream electrical signal and an amplitude of the downstream electrical signal. FIGURE OF THE ABSTRACT: Fig.2

Description

Title of the invention: Flow measurement by amplitude difference

[0001] The invention relates to the field of ultrasonic fluid meters.

[0002] BACKGROUND OF THE INVENTION

[0003] An ultrasonic fluid meter very conventionally comprises a conduit in which the fluid circulates, and an ultrasonic measuring device comprising an upstream transducer (network side) and a downstream transducer (subscriber installation side). Each transducer successively plays the role of an emitter and a receiver of ultrasonic signals. The upstream transducer thus emits an ultrasonic signal into the conduit, which is received by the downstream transducer after having traveled a predefined path (of perfectly controlled length) in the fluid. Then, the downstream transducer in turn emits an ultrasonic signal, which is received by the upstream transducer after having traveled the predefined path (in the other direction) in the fluid. The ultrasonic measuring device then evaluates the speed of the fluid from the transit times of the ultrasonic signals, then the flow rate of the fluid from the speed of the fluid.Estimating the fluid flow rate allows you to evaluate and bill the quantity of fluid consumed.

[0004] The operating principle of the ultrasonic measuring device is therefore based on the measurement of the transit times of the ultrasonic signals between the two transducers. The basic equations are as follows:

[0005] v = L / (t_AB - t_BA) (equation 1),

[0006] where v is the fluid velocity, L is the distance between the transducers, t_AB is the transit time between the upstream transducer and the downstream transducer, and t_BA is the transit time between the downstream transducer and the upstream transducer.

[0007] Q = A * v (equation 2)

[0008] where Q is the volumetric flow rate and A is the cross-sectional area of ​​the duct.

[0009] The measurement of transit times is conventionally carried out using a method of “Zero Crossing”, which requires detecting alternations in the received signal.

[0010] This method may require measurements to be made with a resolution / accuracy of the order of picoseconds. It is therefore necessary to integrate an ASIC into the ultrasonic measuring device, which increases its cost.

[0011] Furthermore, the measurement of transit times is sensitive to the presence of bubbles or impurities in the fluid, which can create alternation jumps, thus distorting the flow measurement.

[0012] [Fig.l] shows an electrical signal produced by one of the transducers upon receipt of an ultrasonic signal having traveled the predefined path.

[0013] The ultrasonic measuring device triggers the analysis of the ultrasonic signal (and in particular the counting of the alternations) from the detection of the first al If an alternation jump occurs, the analysis is triggered, for example, from the second alternation, which significantly degrades the accuracy of the measurement.

[0014] To solve this problem, it is known to use filtering modules to filter problematic measurements. These filtering modules are relatively complex to design and require a certain amount of computing power. In addition, these filtering modules have a certain number of weaknesses. For example, it is possible that a user, occasionally, consumes a very high flow rate of fluid, significantly higher than their usual consumption. The measurement of this flow rate then risks being filtered and not taken into account by the meter; the peak flow rate is then not billed.

[0015] SUBJECT OF THE INVENTION

[0016] The object of the invention is to reduce the cost of an ultrasonic fluid meter or to increase the accuracy of the measurements. Summary of the invention

[0017] With a view to achieving this aim, a measuring method is proposed, implemented in a meter comprising a conduit in which a fluid circulates and an ultrasonic measuring device comprising an upstream transducer and a downstream transducer, the measuring method comprising the steps of:

[0018] - apply an electrical excitation signal to the terminals of the upstream transducer of so that it generates an upstream ultrasonic signal in the conduit, and acquires a downstream electrical signal produced by the downstream transducer when the latter receives the upstream ultrasonic signal;

[0019] - apply the electrical excitation signal to the terminals of the downstream transducer so that that it generates a downstream ultrasonic signal in the conduit, and acquires an upstream electrical signal produced by the upstream transducer when the latter receives the downstream ultrasonic signal;

[0020] - evaluate a flow rate of the fluid in the conduit as a function of a first value represented indicative of a difference between an amplitude of the upstream electrical signal and an amplitude of the downstream electrical signal.

[0021] The measuring method therefore evaluates the flow rate as a function of a difference in amplitude between the upstream and downstream electrical signals. The difference in amplitude is for example a voltage difference, which is relatively simple to measure and for which the required precision does not require the use of an ASIC (this measurement can for example be carried out by a microcontroller). It is therefore possible to reduce the cost of the ultrasonic measuring device and therefore of the meter.

[0022] The flow rate can also be evaluated by additionally using a difference between the upstream and downstream transit times. In this case, the cost of the measuring device is not reduced. trasonic, but the accuracy is greatly improved and the flow rate assessment is consolidated by using both quantities.

[0023] We further propose a measuring method as previously described, further comprising the steps of:

[0024] - measure an upstream transit time of the upstream ultrasonic signal between the transducer upstream and downstream transducer;

[0025] - measure a downstream transit time of the downstream ultrasonic signal between the transducer downstream and the upstream transducer;

[0026] - evaluate the flow rate of the fluid as a function of both the first value, and a second value representing a difference between the upstream transit time and the downstream transit time.

[0027] A measuring method is further proposed as previously described, in which the evaluation of the flow rate of the fluid is carried out, from the first value and the second value, using a multiple regression model.

[0028] We further propose a measuring method as previously described, comprising the steps of:

[0029] - measure the first value;

[0030] - produce a first evaluation of the flow rate of the fluid using the first value;

[0031] - measure the second value;

[0032] - produce a second evaluation of the fluid flow rate using the second value ;

[0033] - evaluate a third value representative of a difference or a ratio between the first assessment and the second assessment;

[0034] - if the third value is greater than a predetermined threshold, do not take into account the first value and the second value;

[0035] - if the third value is less than the predetermined threshold, produce an evaluation consolidated fluid flow rate as a function of the first value and the second value.

[0036] We further propose a measuring method as previously described, in which the third value is equal to: (Q2 - Q1) / (Q2),

[0037] where Q1 is the first evaluation and Q2 is the second evaluation.

[0038] We further propose a fluid meter comprising a conduit in which the fluid circulates, an ultrasonic measuring device comprising an upstream transducer and a downstream transducer, and a processing unit in which the measuring method as previously described is implemented.

[0039] A computer program is further provided comprising instructions which cause the processing unit of the meter as previously described to execute the steps of the measuring method as previously described.

[0040] A computer-readable recording medium is further provided, on which the computer program as previously described is recorded.

[0041] The invention will be better understood in light of the following description of a particular non-limiting embodiment of the invention. Brief description of the drawings

[0042] Reference will be made to the attached drawings, among which:

[0043] [Fig. 1] [Fig. 1] represents an electrical signal produced by a transducer when it captures an ultrasonic signal;

[0044] [Fig.2] [Fig.2] represents an ultrasonic water meter;

[0045] [Fig.3] [Fig.3] represents a graph comprising a curve of the difference amplitude between the upstream and downstream electrical signals, depending on the flow rate;

[0046] [Fig.4] [Fig.4] represents a graph comprising a curve of the signal upstream electrical signal, and a graph including a curve of the downstream electrical signal;

[0047] [Fig.5] [Fig.5] represents a graph comprising a curve of the difference between upstream and downstream transit times, depending on the flow rate;

[0048] [Fig.6] [Fig.6] represents steps of the measuring method. DETAILED DESCRIPTION OF THE INVENTION

[0049] With reference to [Fig.2], the invention is implemented in an ultrasonic fluid meter 1. The meter 1 is in this case a water meter, which is used to measure the water consumption of a subscriber's installation 2. The water is supplied to the installation 2 by a water distribution network 3.

[0050] The meter 1 comprises a conduit 4 in which the water supplied by the network 3 to the installation 2 circulates. The water circulates in the conduit 4 from upstream to downstream, as indicated by the direction of the arrows F. Here, by "upstream" is meant on the side of the network 3, and by "downstream" is meant on the side of the installation 2.

[0051] The meter 1 comprises a processing unit 5 (electronic and software). The processing unit 5 comprises at least one processing component 5a, which is for example a “generalist” processor, a processor specialized in signal processing (or DSP, for Digital Signal Processor), a microcontroller, or a programmable logic circuit such as an FPGA (for Field Programmable Gate Arrays) or an ASIC (for Application Specified Integrated Circuit). The processing unit 5 also comprises one or more memories 5b, connected to or integrated in the processing component 5a. At least one of these memories 5b forms a computer-readable recording medium, on which is recorded at least one computer program comprising instructions which cause the processing component 5a to execute at least some of the steps of the measurement method which will be described below.

[0052] The meter 1 also comprises an ultrasonic measuring device 6. The device ultrasonic measuring device 6 is used to measure the water flow supplied to installation 2 by network 3.

[0053] The ultrasonic measuring device 6 comprises an upstream transducer 7a and a downstream transducer 7b. The ultrasonic measuring device 6 also comprises a calculation module 9, integrated here in the processing unit 5, which carries out the flow rate evaluations.

[0054] The upstream transducer 7a and the downstream transducer 7b are advantageously (but not necessarily) paired. The upstream transducer 7a and the downstream transducer 7b are here piezoelectric transducers.

[0055] Each transducer 7a, 7b successively plays the role of a transmitter and a receiver of ultrasonic signals.

[0056] The processing unit 5 generates an electrical excitation signal Se, and provides the transmitter with the electrical excitation signal. The transmitter then generates an ultrasonic signal Su. The receiver receives the ultrasonic signal after it has traveled a predefined path in the fluid.

[0057] The predefined path is here a direct path (parallel to a longitudinal axis of the duct 4, as is the case in [Fig.2], or inclined to said axis). The predefined path could also be an indirect path: the ultrasonic signals are reflected against the internal wall of the duct 4 (possibly against reflectors themselves located on the internal wall).

[0058] The predefined path has a length L, which is known very precisely.

[0059] Thus, the processing unit 5 first applies the electrical excitation signal to the terminals of the upstream transducer 7a so that the latter generates an upstream ultrasonic signal in the conduit 4. The processing unit 5 acquires a downstream electrical signal produced by the downstream transducer 7b when the latter receives the upstream ultrasonic signal.

[0060] Then, the processing unit 5 applies the electrical excitation signal to the terminals of the downstream transducer 7b so that the latter generates a downstream ultrasonic signal in the conduit 4. The processing unit 5 acquires an upstream electrical signal produced by the upstream transducer 7a when the latter receives the downstream ultrasonic signal.

[0061] The processing unit 5 analyzes the downstream electrical signal and the upstream electrical signal to evaluate the flow rate of the water in the conduit 4.

[0062] A new way to evaluate flow rate has been identified.

[0063] It has been found, following numerous tests and numerous investigations and analyses, that the flow rate of the fluid can be evaluated from a value representative of the difference between the amplitude of the upstream electrical signal and the amplitude of the downstream electrical signal.

[0064] [Fig. 3] shows the correlation between the difference in amplitude and the flow rate. Curve Cl was obtained by a large number of measurements carried out on a large number of meters.

[0065] When an alternation jump occurs, the amplitude difference does not follow this linear correlation, indicating that the measurement is distorted.

[0066] We see the upstream electrical signal S_am and the downstream electrical signal S_av in [Fig.4],

[0067] Here, by "amplitude" of the electrical signal (upstream or downstream), we mean a value representative of a peak-peak amplitude of the electrical signal (upstream or downstream) when a variation of said peak-peak amplitude becomes lower than a predefined variation threshold (which for example is equal to 5% or 10%).

[0068] This is for example an average value of the peak-peak amplitude in a predefined zone Z, located between a preliminary zone Zp and a final zone Zf of the electrical signal (upstream or downstream). Here, the predefined zone includes for example the lobes between the 12th lobe and the 31st lobe.

[0069] It could also be the peak-peak amplitude between a predetermined positive lobe and negative lobe, for example the 22nd positive lobe and the following negative lobe.

[0070] It could also be an average of the maximum amplitudes of positive lobes in a predefined area, or the maximum amplitude of a predefined lob, etc.

[0071] In [Fig.4], we see that the peak-peak amplitude in the predefined zone of the upstream electrical signal S_am is equal to 700 mV and that the peak-peak amplitude of the downstream electrical signal S_av is equal to 665 mV.

[0072] The origin of the amplitude difference of the upstream and downstream electrical signals in the flow can be attributed to dispersion, which is a phenomenon that causes the amplitude of the ultrasonic signals to change as they propagate through the fluid. Dispersion is influenced by the characteristics of the fluid, such as viscosity, density and the presence of bubbles or impurities.

[0073] Thus, the measuring method consists of evaluating a flow rate of the fluid in the conduit 4 as a function of a first value representative of a difference between an amplitude of the upstream electrical signal S_am and an amplitude of the downstream electrical signal S_av.

[0074] We can use the following equation:

[0075] AV = 0.0079 x flow rate - 0.0477 (equation 1),

[0076] where AV is a difference between the amplitude of the upstream electrical signal S_am and the amplitude of the downstream electrical signal S_av (the amplitude of each signal being the average of the peak-peak amplitude in the predefined zone).

[0077] The processing unit 5 therefore evaluates the flow rate of water in the conduit 4 as a function of a first value representative of a difference between the amplitude of the upstream electrical signal and an amplitude of the downstream electrical signal.

[0078] Here, to consolidate the measurement, the processing unit 5 also uses the transit times to evaluate the water flow rate.

[0079] The processing unit 5 analyzes the downstream electrical signal S_av to measure the time upstream transit time between the upstream transducer 7a and the downstream transducer 7b, and the upstream electrical signal S_am to measure the downstream transit time between the downstream transducer 7b and the upstream transducer 7a.

[0080] In [Fig.5] we see curve C2 which represents the correlation between the flow rate and the difference between the transit times.

[0081] For example, we can use the following equation:

[0082] DTOF = 0.0876 x flow rate + 0.686 (equation 2),

[0083] where DTOF is the difference between the upstream transit time and the downstream transit time.

[0084] The processing unit 5 therefore evaluates the water flow rate as a function of both the first value representative of the difference between the amplitude of the upstream electrical signal and the amplitude of the downstream electrical signal, and a second value representative of the difference between the upstream transit time and the downstream transit time.

[0085] We therefore have two equations:

[0086] AV = 0.0079 x flow rate - 0.0477 (equation 1)

[0087] DTOF = 0.0876 x flow rate + 0.686 (equation 2).

[0088] To improve the accuracy of the measurement, the processing unit 5 can combine the amplitude difference measurements with the transit time difference measurements.

[0089] A multiple regression model is used for this.

[0090] The multiple regression model is a statistical method used to analyze the relationships between several variables. Here, we have two independent variables (AV and DTOF) and one dependent variable (flow rate). It is possible to use a multiple regression model to estimate the flow rate from the AV and DTOF measurements.

[0091] A multiple linear regression model is used here:

[0092] flow = a * (DTOF - 0.686) + b * (Av + 0.0477)

[0093] In this example, "a" and "b" are the regression coefficients to be determined from of the measurements taken. This multiple regression model combines the information from the two inverted equations to estimate the flow rate based on both AV and DTOF measurements simultaneously. Unlike univariate models, this model allows the information provided by the two independent variables to be used to obtain a more accurate and reliable estimate of the flow rate.

[0094] To calibrate this model, a data set containing flow, AV and DTOF measurements is required. Using this data, it is possible to determine the coefficients "a" and "b" that minimize the sum of the squared errors between the observed flow rates and the flow rates predicted by the model.

[0095] Once the model is calibrated, it can be used to estimate the flow rate from new AV and DTOF measurements.

[0096] The coefficients "a" and "b" are determined in the factory using data produced by a certain number of counters (for example 100 counters), which are represented representative of the meters that will be mass-produced (same hydraulics, identical transducers, same geometry, etc.). The model equation is injected into the calculation module 9 of the processing unit 5, which will then recover the DTOF and AV measurements, and calculate the flow rate.

[0097] As an example, using both equations 1 and 2, we obtain:

[0098] flow rate = (AV + 0.0477) / 0.0079 (from equation 1)

[0099] flow rate = (DTOF - 0.686) / 0.0876 (from equation 2)

[0100] We equate these two expressions for the flow rate, and we obtain:

[0101] (DTOF - 0.686) / 0.0876 = (AV + 0.0477) / 0.0079

[0102] We can simplify this equation to obtain:

[0103] DTOF x 0.0079 - AV x 0.0876 = 0.005246

[0104] By rearranging this equation, we finally obtain an expression for the flow rate as a function of AV and DTOF:

[0105] Flow = (0.0876 x AV + 0.0079 x DTOF - 0.005246) / 0.0803

[0106] We therefore obtain a third equation:

[0107] flow rate = (0.0876 x AV + 0.0079 x DTOF - 0.005246) / 0.0803, and therefore

[0108] flow rate = 1.09 AV + 0.098 DTOF - 0.0653 (equation 3).

[0109] The processing unit 5 can therefore produce a consolidated evaluation of the water flow rate as a function of the first value (difference between the amplitudes) and the second value (difference between the transit times).

[0110] The processing unit 5 can further determine whether the flow measurement is accurate or incorrect.

[0111] For this, we use the two equations which link the flow rate to the DTOF and the flow rate to the AV:

[0112] flow rate = (AV + 0.0477) / 0.0079 (from equation 1)

[0113] flow rate = (DTOF - 0.686) / 0.0876 (from equation 2)

[0114] Each time the processing unit 5 measures a DTOF and an AV, the processing unit 5 will evaluate the two flow rates separately and, if a value representative of a difference or a ratio between the two results is less than a predetermined threshold (for example equal to 5%), the processing unit 5 considers that the evaluations are valid and produces a consolidated evaluation using equation 3.

[0115] On the other hand, if the value representing a difference or a ratio between the two results is greater than this predetermined threshold, the measurement will be considered erroneous and will therefore be rejected by the processing unit 5. The processing unit 5 will replace the erroneous measurement with the last valid measurement and will raise an alarm to signal the rejected measurement by indicating the difference observed between the two flow rates resulting from the two equations.

[0116] The measuring method is now described, with reference to [Fig.6].

[0117] The processing unit 5 measures a first value representative of a difference between an amplitude of the upstream electrical signal and an amplitude of the downstream electrical signal: step E1. The first value is here equal to this difference AV.

[0118] Then, the processing unit 5 produces a first evaluation Q1 of the water flow rate using the first value AV: step E2.

[0119] The processing unit 5 measures a second value representative of a difference between the upstream transit time and the downstream transit time: step E3. The second value is here equal to this difference DTOF.

[0120] Then, the processing unit 5 produces a second evaluation Q2 of the water flow rate using the second value: step E4.

[0121] The processing unit 5 evaluates a third value representative of a difference or a ratio between the first evaluation and the second evaluation: step E5.

[0122] Here, this third value is equal to:

[0123] (Q2-Q1) / (Q2),

[0124] Where Q1 is the first water flow rate estimation and Q2 is the second water flow rate estimation.

[0125] The processing unit 5 compares this third value with the predetermined threshold (of 5% for example).

[0126] If this third value is greater than the predetermined threshold (here greater than or equal), the processing unit 5 refuses the measurement: step E6. The processing unit 5 does not take into account the first value and the second value. The processing unit 5 generates an alarm indicating that the measurement is aberrant: step E7. The processing unit 5 replaces the “present” evaluation of the water flow rate with the last valid evaluation: step E8.

[0127] In step E5, if the third value is lower than the predetermined threshold (here strictly), the processing unit 5 produces a consolidated evaluation Q3 as a function of the first value and the second value: step E9. The processing unit 5 uses equation 3.

[0128] The process ends: step E10.

[0129] The invention has the following advantages.

[0130] The flow rate evaluation can be carried out using only the amplitude differences of the upstream and downstream electrical signals. This way of evaluating the flow rate does not require the use of an ASIC, which can reduce the cost of the ultrasonic measuring device 6 and therefore of the meter 1.

[0131] The invention also makes it possible to improve the accuracy of the flow rate evaluation. By combining the information from the AV and the DTOF, the method and device of the invention make it possible to improve the accuracy of ultrasonic meters, thus reducing measurement errors caused by alternation jumps and weaknesses of the traditional filtering modules.

[0132] The invention in fact makes it possible to check whether a flow measurement is accurate or erroneous (for example due to an alternation jump created by an air bubble, a temperature variation, or a poorly configured trigger).

[0133] The invention makes it possible to filter an aberrant measurement point by combining the two pieces of information (amplitude difference, transit time difference).

[0134] The invention also makes it possible to protect the fluid distributor against loss of revenue. Unlike traditional filtering modules, which can allow high unbilled flow rates to pass through, the method of the invention makes it possible to detect and correct measurement errors linked to alternation jumps, thus ensuring more accurate and equitable billing.

[0135] The approach proposed by the invention is simpler and easier to implement than the complex filtering modules traditionally used to solve this problem. The measurement of the ultrasonic signals is possibly already carried out to determine the transit time (in the case where the measurement uses both the transit times and the amplitude difference), and the use of these signals to calculate the upstream and downstream amplitude deviation does not require additional measurements. Thus, this method fully exploits existing data, without adding additional complexity or costs to the instrumentation or data processing.

[0136] The method and device of the invention can be applied to different types of ultrasonic and fluid meters, thus providing a versatile solution for improving the accuracy of flow measurements.

[0137] By improving the accuracy of ultrasonic meters, the invention makes it possible to save money by reducing measurement errors and improving water resource management.

[0138] Of course, the invention is not limited to the embodiment described but encompasses any variant falling within the scope of the invention as defined by the claims.

[0139] The invention is of course applicable regardless of the positioning and configuration of the upstream transducer and the downstream transducer. The ultrasonic signals can be emitted with an orientation of any angle relative to a longitudinal axis of the conduit.

[0140] The predefined path between the transducers is not necessarily a direct path. The ultrasonic signals, emitted and received in the conduit by the transducers, could for example be reflected by reflectors (for example by mirrors oriented at 45°).

[0141] The invention does not of course apply only to a water meter, but to any meter for any fluid: gas, oil, etc.

[0142] A multivariate linear regression model was used to evaluate the flow rate as a function of DTOF and AV. The flow rate could be evaluated differently from these quantities, for example by using a Kalman filter or a weighted average filter.

[0143] It has been indicated that the first value is representative of a difference between an amplitude of the upstream electrical signal and an amplitude of the downstream electrical signal. It is therefore not necessarily the difference between the amplitude of the upstream electrical signal and the amplitude of the downstream electrical signal. It could for example be the

[0144] difference between the amplitude of the downstream electrical signal and the amplitude of the upstream electrical signal.

[0145] This is also true for the second value representative of a difference between the upstream transit time and the downstream transit time, and for the third value representative of a difference or a ratio between the first evaluation and the second evaluation.

Claims

Claims

1. A measuring method, implemented in a meter (1) comprising a conduit (4) in which a fluid circulates and an ultrasonic measuring device (6) comprising an upstream transducer (7a) and a downstream transducer (7b), the measuring method comprising the steps of: - applying an electrical excitation signal (Se) to the terminals of the upstream transducer so that the latter generates an upstream ultrasonic signal in the conduit, and acquiring a downstream electrical signal (S_av) produced by the downstream transducer when the latter receives the upstream ultrasonic signal; - applying the electrical excitation signal to the terminals of the downstream transducer so that the latter generates a downstream ultrasonic signal in the conduit, and acquiring an upstream electrical signal (S_am) produced by the upstream transducer when the latter receives the downstream ultrasonic signal;- evaluate a flow rate of the fluid in the conduit as a function of a first value (AV) representative of a difference between an amplitude of the upstream electrical signal and an amplitude of the downstream electrical signal.;

2. A measuring method according to claim 1, further comprising the steps of: - measuring an upstream transit time of the upstream ultrasonic signal between the upstream transducer (7a) and the downstream transducer (7b); - measuring a downstream transit time of the downstream ultrasonic signal between the downstream transducer (7b) and the upstream transducer (7a); - evaluating the flow rate of the fluid as a function of both the first value, and a second value (DTOF) representative of a difference between the upstream transit time and the downstream transit time.

3. A measuring method according to claim 2, wherein the evaluation of the fluid flow rate is carried out, from the first value and the second value, using a multiple regression model.

4. A measuring method according to claim 2, comprising the steps of: - measuring the first value (AV); - producing a first evaluation (Ql) of the fluid flow rate using the first value; - measuring the second value (DTOF); - producing a second evaluation (Q2) of the fluid flow rate using the second value; - evaluating a third value representative of a difference or a ratio between the first assessment and the second assessment; - if the third value is greater than a predetermined threshold, disregard the first value and the second value; - if the third value is less than the predetermined threshold, produce a consolidated assessment (Q3) of the fluid flow rate as a function of the first value and the second value.

5. A measuring method according to claim 4, wherein the third value is equal to: (Q2 - Q1) / (Q2), where Q1 is the first evaluation and Q2 is the second evaluation.

6. Fluid meter comprising a conduit (4) in which the fluid circulates, an ultrasonic measuring device (6) comprising an upstream transducer (7a) and a downstream transducer (7b), and a processing unit (5) in which the measuring method according to one of the preceding claims is implemented.

7. Computer program comprising instructions which cause the processing unit (5) of the meter (1) according to claim 6 to execute the steps of the measuring method according to one of claims 1 Q

8. 1 d J. Computer-readable recording medium, on which the computer program according to claim 7 is recorded.

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