Method for measuring the flow rate of a fluid in a pipe
A method is provided for measuring the flow rate of a fluid in a pipe using at least two ultrasonic transducers. The method includes a succession of cycles ( 35 ) of transmissions, each comprising a sub-cycle A in which an ultrasonic wave is transmitted by a first transducer and a sub-cycle B in which an ultrasonic wave is transmitted by a second transducer. The propagation times of these two waves are measured, wherein the order between the sub-cycle A and the sub-cycle B is reversed between the successive transmission cycles, and a flow rate is calculated from an average of: a difference between the two measured propagation times of a given transmission cycle, and a difference between the two measured propagation times of a second transmission cycle following the given transmission cycle.
1 . A method for measuring the flow rate of a fluid in a pipe, the flow rate being measured using at least two ultrasound transducers,
the method comprising generating successive cycles, referred to as transmission cycles, which is controlled by a control unit, each transmission cycle comprising:
a subcycle A comprising:
a step of a first ultrasound transducer from among said at least two ultrasound transducers transmitting an ultrasound wave,
a step of a second ultrasound transducer from among said at least two ultrasound transducers receiving said ultrasound wave,
a step of measuring a time for the ultrasound wave to be propagated from the first ultrasound transducer to the second ultrasound transducer,
a subcycle B comprising:
a step of the second ultrasound transducer transmitting an ultrasound wave,
a step of the first ultrasound transducer receiving said ultrasound wave,
a step of measuring a time for the ultrasound wave to be propagated from the second ultrasound transducer to the first ultrasound transducer,
the first subcycle A and the subcycle B of the same transmission cycle succeeding one another in a given order,
wherein the order of the subcycle A and the subcycle B of a given transmission cycle is reversed with respect to the order of the subcycle A and the subcycle B of a transmission cycle directly preceding said given transmission cycle,
and in that said method comprises at least one fluid flow rate computation step in which a flow rate of the fluid flowing in the pipe is computed on the basis of an average between:
a difference between the propagation time measured for the subcycle A and the propagation time measured for the subcycle B of the same given transmission cycle, and
a difference between the propagation time measured for the subcycle A and the propagation time measured for the subcycle B of the same transmission cycle directly succeeding the given transmission cycle,
wherein a given first transmission cycle is separated from a second transmission cycle directly preceding the first transmission cycle by a duration, referred to as the intercycle duration, which is greater than or equal to 15 ms,
said method further comprising a step of at least partially putting the control unit on standby between a first transmission cycle and a second transmission cycle,
wherein when the control unit is turned on, the subcycle A and the subcycle B are each carried out over a stabilization period of the electronic components of the control unit, the ultrasound wave transmitted during the subcycle A and the ultrasound wave transmitted during the subcycle B of each transmission cycle each being transmitted over a predefined transmission time interval.
2 . The method as claimed in claim 1 , wherein said intercycle duration is between 125 ms and 2000 ms.
3 . The method as claimed in claim 1 , in which the subcycle A and the subcycle B of the same transmission cycle are separated from one another by a duration, referred to as the intracycle duration, which is less than or equal to 10 ms.
4 . The method as claimed in claim 3 , wherein said intracycle duration is between 1 ms and 10 ms.
5 . The method as claimed in claim 1 , wherein the predefined transmission time interval is less than 1 μs.
6 . The method as claimed in claim 1 , in which the ultrasound wave is generated by a transducer operating as a transmitter on the basis of a square electrical pulse.
7 . The method as claimed in claim 1 , in which the fluid flow rate is determined on the basis of a predetermined table in which propagation time difference results are associated with flow rates.
8 . A flowmeter comprising:
at least two ultrasound transducers which are adapted to be joined to a pipe,
a control unit programmed to control generation of successive cycles, referred to as transmission cycles, each transmission cycle comprising:
a subcycle A comprising:
a step of a first ultrasound transducer from among said at least two ultrasound transducers transmitting an ultrasound wave,
a step of a second ultrasound transducer from among said at least two ultrasound transducers receiving said ultrasound wave,
a step of measuring a time for the ultrasound wave to be propagated from the first ultrasound transducer to the second ultrasound transducer,
a subcycle B comprising:
a step of the second ultrasound transducer transmitting an ultrasound wave,
a step of the first ultrasound transducer receiving said ultrasound wave,
a step of measuring a time for the ultrasound wave to be propagated from the second ultrasound transducer to the first ultrasound transducer,
the subcycle A and the subcycle B of the same transmission cycle succeeding one another in a given order,
wherein the order of the subcycle A and the subcycle B of a given transmission cycle is reversed with respect to the order of the subcycle A and the subcycle B of a transmission cycle directly preceding said given transmission cycle,
wherein a given first transmission cycle is separated from a second transmission cycle directly preceding the first transmission cycle by a duration, referred to as the intercycle duration, which is greater than or equal to 15 ms,
and in that the control unit is programmed to carry out at least one fluid flow rate computation step in which a flow rate of the fluid flowing in the pipe is computed on the basis of an average between:
a difference between the propagation time measured for the subcycle A and the propagation time measured for the subcycle B of the same given transmission cycle, and
a difference between the propagation time measured for the subcycle A and the propagation time measured for the subcycle B of the same transmission cycle directly succeeding the given transmission cycle,
said control unit being at least partially on standby between a first transmission cycle and a second transmission cycle,
wherein when the control unit is turned on, the subcycle A and the subcycle B are each carried out over a stabilization period of the electronic components of the control unit and in the same state of instability of the electronic components of the control unit, the ultrasound wave transmitted during the subcycle A and the ultrasound wave transmitted during the subcycle B of each transmission cycle each being transmitted over a predefined transmission time interval.
9 . The flowmeter as claimed in claim 8 , wherein said flowmeter comprises said pipe on which the two ultrasound transducers are mounted, this pipe having two longitudinal ends comprising a connecting member.