Acoustic transducer arrangement including respective transducer set for each edge of a notational regular polygon

1. An arrangement of acoustic transducers in a flow meter used in water irrigation, the flow meter providing measurement of a rate at which water is flowing, the arrangement comprising:

a respective transducer set for each edge of a notional regular polygon, the transducer sets being mounted in a tubular cavity to carry the water, each of the transducer sets respectively including:

two acoustic transducers oriented to provide only a single acoustic path with each other and lying in a measurement plane of the respective set; and

another two acoustic transducers oriented to provide only another single acoustic path with each other and lying in the measurement plane of the respective set;

the transducer sets being positioned so that, in a cross-section normal to the tubular cavity, the measurement plane of each respective transducer set is coincident with a respective edge of the notional regular polygon;

transducer units, each respective one of the transducer units carries two of the acoustic transducers and includes:

a mounting arrangement by which the respective one transducer unit is mounted as a unit inside a wall of the tubular cavity;

a mounting plate, which is curved to complement an exterior of the wall of the tubular cavity; and

a transducer-carrying portion projecting through a complementary opening through the wall of tubular cavity.

2. The arrangement of claim 1 wherein the acoustic path of each respective set substantially crosses the other acoustic path of the respective set.

3. The arrangement of claim 1 , wherein the acoustic path of each respective set is substantially perpendicular to the other acoustic path of the respective set.

4. The arrangement of claim 1 , wherein the notional regular polygon is substantially concentric to the tubular cavity.

5. The arrangement of claim 1 , wherein the notional regular polygon is convex.

6. The arrangement of claim 1 , wherein the regular polygon is a square.

7. The arrangement of claim 1 , wherein the measurement planes are substantially parallel to the tubular cavity.

8. The arrangement of claim 1 , further comprising four acoustic transducers oriented to define two acoustics paths lying in a plane coincident with a center line of the tubular cavity.

9. The arrangement of claim 8 wherein each upstream acoustic transducer, of the sets and of the further four acoustic transducers, lies in an upstream plane transverse to the tubular cavity; and

each downstream acoustic transducer, of the sets and of the further four transducers, lies in a downstream plane transverse to the tubular cavity.

10. An arrangement of hardware including the arrangement of claim 1 and a sensor for sensing a level of the water in the tubular cavity.

11. An assembly for a flow meter including the arrangement of claim 1 and a body defining the tubular cavity and carrying the acoustic transducers.

12. The assembly of claim 11 , wherein the body defines a respective mounting face portion for each of the acoustic transducers of the sets; each of the mounting face portions being substantially normal to a respectively corresponding edge portion of the notional regular polygon.

13. A flow meter including the arrangement of claim 1 and a logic arrangement for applying logic to outputs from the transducers to produce an indication of the rate at which the water is flowing.

14. The flow meter of claim 13 wherein the logic is at least partly determined by system identification.

15. A flow control unit including the flow meter of claim 13 ; and a flow control barrier to control movement of water therewithin.

16. The flow control unit of claim 15 wherein said flow control barrier is a knife gate valve.

17. The flow control unit of claim 15 wherein said flow control barrier is a bi-fold gate valve.

18. A transducer unit for a flow meter, the flow meter being for measuring a rate at which water is flowing; the transducer unit comprising:

a first acoustic transducer to send signals along, and receive signals from, an acoustic path;

a second acoustic transducer to send signals along, and receive signals from, another acoustic path; and

a mounting arrangement by which the transducer unit is mountable as a unit and in association with a tubular cavity for carrying the water;

a mounting plate, which is curved to complement an exterior of a wall of the tubular cavity; and

a transducer-carrying portion projecting through a complementary opening through the wall of tubular cavity;

the acoustic paths mutually diverging away from the transducer unit at orientations, relative to the mounting arrangement, such that an upstream at least three of the transducer units is co-operable with a downstream at least three of the transducer units; and

a body defining the tubular cavity to form an arrangement of acoustic transducers, including the first and second acoustic transducers, the arrangement of acoustic transducers comprising:

a respective transducer set for each edge of a notional regular polygon, the transducer sets being mounted in the tubular cavity to carry the water, each of the transducer sets respectively including:

two acoustic transducers of the arrangement of acoustic transducers, which are oriented to provide only a single acoustic path with each other and lying in a measurement plane of the respective set; and

another two acoustic transducers of the arrangement of acoustic transducers, which are oriented to provide only another single acoustic path with each other and lying in the measurement plane of the respective set;

the transducer sets being positioned so that, in a cross-section normal to the tubular cavity, the measurement plane of each respective transducer set is coincident with a respective edge of the notional regular polygon.