WO2012048660A1

WO2012048660A1 - Anemometer

Info

Publication number: WO2012048660A1
Application number: PCT/CN2011/080803
Authority: WO
Inventors: De Tian Su; Shek Fai Yeung; Ping Chiu Chan
Original assignee: Chiaphua Components (Shenzhen) Limited
Priority date: 2010-10-15
Filing date: 2011-10-14
Publication date: 2012-04-19
Also published as: CN102455367A; CN102455367B

Abstract

An anemometer comprises a rigid mount (10); a sensor plate (12) mounted for movement relative to the rigid mount (10), the sensor plate (12) having an outer surface which is substantially symmetrical about a first axis; a load sensor (17) to sense a wind load on the sensor plate (12); a deflector (15) having a tapered surface with an axis of symmetry substantially coaxial with the first axis (13), wherein, the deflector (15) is disposed adjacent the sensor plate (12) and aligned, and the tapered surface tapers inwardly towards the sensor plate (12), so that a wind stream in any direction in an incident plane perpendicular to the first axis (13) is deflected toward the sensor plate (12) and a proportion of the flow in the incident plane impinges on the sensor plate (12); and receiving and transmitting means configured to receive signals from the load sensor (17) and transmit an output signal indicative of wind speed.

Description

ANEMOMETER Technical field

The present invention relates to an anemometer.

Background of the Invention Anemometers are used to measure air flow and commonly comprise a rotating element whose angular speed of rotation is correlated with the linear velocity of the air flow. One of the drawbacks of cup or rotor anemometers of this type is that the inertia of the mechanical mechanism must be overcome. As a result of its reliance on this mechanical element, the anemometer is not conducive to measuring gusts, and is subject to errors in measurement due to overshoot, oscillations that occur due to change in wind direction, and wind measurement even when the wind is not blowing.

Target-type anemometers are also used to measure wind speed by measuring the amount of force exerted by the wind on a target located in the air stream. The force exerted on the target by the air stream is proportional to the pressure drop across the target, and to the wind speed. For instance, US patent no. 4631958 describes an anemometer having a spherical target mounted to an upright shaft, with the wind force tending to deflect the target downstream, thereby moving the shaft away from its upright position. Although a relatively low-cost device, the accuracy of measurement is modest. Moreover, the device is sensitive to inclinations of the base, and has no built in compensatory mechanism for correcting the inaccuracies that would result.

Japanese patent publication no. 60166869A describes a combined anemometer and wind direction sensor comprising a cylindrical body in which pressure chambers are formed, bounded by parallel diaphragms disposed in transverse planes. Air inlet and outlet ports in each pressure chamber are aligned on respective transverse axes, the axes being at different angles to one another, such that flow in any direction produces a different pressure in each of the pressure chambers. The wind speed and direction is calculated from the resulting pressure profile as measured by strain gauges fixed to the diaphragms. One drawback to this design is the excessive use of strain gauges contributing to the overall complexity of the design. Moreover, for proper performance the small inlet and outlet ports must be unobstructed, and a louvred cover extends about the cylindrical body to cover and protect the ports in this respect. However, given the configuration, visual inspection for lack of obstruction is difficult to perform.

It is an object of the invention to provide an anemometer of relatively simple, compact, robust, durable and low-cost construction. In particular, there is a need for a versatile anemometer, able to be mounted in different positions and orientations, which may be permanently installed or portable and which is suitable for unattended operation. It is a further object of the present invention to overcome or substantially ameliorate the above disadvantages or, more generally, to provide an improved anemometer.

Disclosure of the Invention

According to one aspect of the present invention there is provided an anemometer comprising: a rigid mount; a sensor plate mounted for movement relative to the rigid mount, the sensor plate having an outer surface which is substantially symmetrical about a first axis; a load sensor to sense a wind load on the sensor plate; a deflector having a tapered surface with an axis of symmetry substantially coaxial with the first axis, the deflector being disposed adjacent the sensor plate and aligned so that the tapered surface tapers inwardly towards the sensor plate whereby a wind stream in any direction in an incident plane perpendicular to the first axis is deflected toward the sensor plate so that a proportion of the flow in the incident plane impinges on the sensor plate; and receiving and transmitting means configured to receive signals from the load sensor and transmit an output signal indicative of wind speed.

In the anemometer of the invention, the air stream deflected by the deflector is directed toward the sensor plate, without contacting any intervening member, providing an open structure the functional elements of which can be readily visually checked for freedom from obstruction. The resulting impulse provided by this air stream tends to displace the sensor plate from its neutral position, and the amount of displacement is measured by the sensor to provide the output signal indicative of wind speed.

Preferably a gap is provided between the deflector and the outer surface of the sensor plate.

Preferably the deflector is conical, most preferably being a concave conical frustum. However, the precise form of the deflector is not essential to the invention. Other axi- symmetric tapered surfaces may be employed within the scope of the invention, such as a pyramid, a concave or convex pyramid, a sphere, a spheroid; a pyramid, sphere, or spheroid frustum; or a complex shape formed by combination of such axi-symmetric forms - for instance, a conical frustum with a domed or partly spherical cap its end. Preferably the surface of the deflector includes an annular peripheral portion and a circular inner portion both lying in respective planes perpendicular to the first axis. Preferably the annular peripheral portion and a circular inner portion are joined by a concave conical surface. Preferably the conical surface portion and circular inner portion are joined by a radiused portion to provide a smooth profile. Preferably the rigid mount includes a recess in which the load sensor is received, and an open mouth which is substantially closed by the sensor plate. Preferably the sensor plate lies in the recess, more preferably entirely within the recess so that no part of the sensor plate projects beyond the boundaries of the rigid mount. The outer surface of the sensor plate is preferably convex, most preferably having a circular periphery. Preferably the deflector is connected to the rigid mount. Most preferably, the deflector is fixedly connected to the rigid mount. However, optionally, the deflector could be mounted for movement relative to the rigid mount, as by a sliding or telescopic coupling extending parallel to the first axis so as to maintain proper alignment between the deflector and sensor plate in different operating positions. Preferably the deflector is fixedly connected to the rigid mount by a plurality of stanchions angularly equally spaced about the first axis and fixed at a periphery of the deflector. In preferred embodiments the deflector comprises a shell, the anemometer further comprising a cap fixed to the shell to enclose a cavity therein. Preferably the cap has a convex outer surface which is substantially symmetrical about the first axis. Advantageously, meteorological instruments, such as sun or rain sensors may be mounted in the cavity

The load sensor is a transducer which converts force into a measurable electrical output which may be positioned substantially beneath the sensor plate, and is preferably a strain gauge based load sensor. Preferably the load sensor comprises a bending beam load cell, so as to provide a compact anemometer. Optionally other types of load cell may be employed.

The receiving and transmitting means may simply provide for directly transmitting the output from the load sensor, as by wired connection to an output port on the anemometer, or by wireless communication. However, preferably the receiving and transmitting means comprises a processing circuit which determines wind speed inferentially based upon a strain measurement made by a load cell. The processing circuit may include a signal processing circuit to filter the signals received from the load sensor and a microcprocessor, as for providing an output signal indicative of wind speed, or for driving an electronic display.

This invention provides an anemometer which is versatile, effective and efficient in operational use, and may be economically constructed. By providing a deflector according to the invention, there is no need for means for orienting the anemometer into the wind, or for responding to movement of a sensor target, as the sensor plate is always suitably located in the air stream. Brief Description of the Drawings

Preferred forms of the present invention will now be described by way of example with reference to the accompanying drawings, wherein:

Figure 1 is a perspective view of a first embodiment of an anemometer according to the invention;

Figure 2 is a longitudinal section through the anemometer of Fig. 1 ;

Figure 3 is an exploded view of the anemometer of Fig. 1 ;

Figure 4 is a perspective view of a second embodiment of an anemometer according to the invention, and Figure 5 is a longitudinal section through the anemometer of Fig. 4.

Description of the Preferred Embodiments

Referring to Fig. 1 , a first embodiment of an anemometer according to the invention comprises a rigid mount 10 which includes an internal recess 1 1 in which is received a weigh plate or sensor plate 12 mounted for movement relative to the mount 10. The sensor plate has a planar, circular outer surface which is substantially symmetrical about a first axis 13. An air deflector 15 is connected to the mount 10 adjacent the sensor plate 12 by three stanchions 14. The stanchions 14 are equally circumferentially spaced around the periphery of the mount, outside of the sensor plate 12 and are of a slender form, such that the deflector 15 and sensor plate 12 are open to the ambient air through openings 16 between adjacent stanchions 14. The deflector 15 generally overlies and covers the sensor plate 12.

As shown in Fig. 2, a load sensor in the form of a bending beam load cell 17 supports the sensor plate 12 to sense a wind force on the sensor plate 12. The deflector 15 has a tapered surface 18 symmetrical about the axis 13 and aligned so that the tapered surface 18 tapers inwardly towards the sensor plate 12. In this manner a wind stream (in any direction in an incident plane perpendicular to the axis 13) which passes through one of the openings 16 is deflected by the deflector 15 toward the sensor plate 12. The resulting flow that impinges on the sensor plate 12 is measured by the load sensor and from this measurement wind speed can be determined inferentially.

The deflector 15 is shaped generally as a concave conical frustum in the embodiment shown, having an annular peripheral portion 19 which lies in a transverse plane 20. A flat, circular inner portion 21 of the deflector lies in a transverse plane 22 disposed inwardly of the plane 20. The concave conical surface 18 joining the peripheral portion 19 to the portion 21 includes a radiused portion 23 to provide a smooth profile. A gap 24 is provided between the opposing parallel surfaces of the deflector 15 and the sensor plate 12.

The deflector 15 is a shell to which a complementary cap 25 is fixed to enclose a cavity 27 therein. The cap 25 has a convex outer surface 26 which is substantially symmetrical about the axis 13. The mount 10, deflector 15, plate 12 and cap 25 are made from relatively rigid materials, such as metal or plastics and are fixed together, as by screw fasteners 29 extending longitudinally through the stanchions 14.

The annular peripheral portion 19 is disposed opposite the annular rim 30 of the mount 10 which extends about the recess 1 1. In this embodiment annular rim 30 is generally coplanar with the inner face 21 of the deflector 15. The recess 1 1 in which the load cell 17 is received has an open mouth facing the deflector 15 and which is substantially closed by the sensor plate 12. The sensor plate 12 lies in the recess 1 1 , in a plane offset inwardly from that of the rim 30 so that no part of the sensor plate 12 projects beyond the boundaries of the rigid mount. The sensor plate 12 may be formed from a base disc 32 fixed to a cover disc 31.

The load cell 17 may comprises two parallel bending beams 33, 34 on top of each other, separated by rigid end blocks 35, 36. The load cell 17 is cantilevered from the mounting bracket 42 supporting one end block, and the other end block supporting load plate 12. Axially oriented strain gauges (not shown) are bonded to each beam near the joints with the end blocks 35, 36. When a load acts on the plate 12, the rigid end pieces force the two bending beams to flex. One strain gauge on each bending beam will accordingly sense tension, while the second strain gauge will sense compression. Four strain gauges may be connected in a bridge circuit (not shown) to provide an output signal used to measure the load. Preferably the load cell 17 is optimised such that the output signal from the bridge circuit is a true measure, or a closes as possible to a true measure, of the vertical component of the load, independent of the position of the centre of pressure of the air stream impinging upon the plate 12 and the direction of the air stream. A processing circuit may be provided on a circuit board 40 mounted within the recess 1 1. The processing circuit may be encapsulated to seal the anemometer. Optionally the load cell may also be sealed, preferably by a soft bellows or encapsulating material that will not have a substantial effect on the measuring sensitivity of the load cell. The processing circuit determines wind speed inferentially based upon a strain measurement made by the load cell 17. The strain gauge bridge circuit is connected to the processing circuit, which in turn may be connected to an outlet port, so that the output signal indicative of measured air speed can be transmitted, as by coupling the anemometer to a computer or stand-alone electronic display. The electronic display may display wind speeds digitally in numerals, or by means of another analog display, light array, or the like. The processing circuit may include a filter circuit for filtering the output from the load cell to extract peak values over a measurement interval. A memory is provided in which a data set relating to wind speed measurements corresponding to load cell outputs is stored. For instance, once a load cell measurement has been made, the peak values may be averaged and a corresponding wind speed can be determined form this mean value by interpolation between two data points stored in memory, before the processor outputs a signal indicative of the determined wind speed. Optionally, each anemometer may be provided with a unique data set, derived by calibrating each anemometer individually. The processing circuit further includes a tilt sensor 52 responsive to the inclination of the anemometer and used to compensate wind speed measurements for variations in inclination of axis 13 from true vertical. For example, a semi-conductor MEMS (micro electronic machined semiconductor) device can be used to provide for the correction details. Figs 4 and 5 illustrate a second embodiment of the anemometer, and to the extent that like elements are provided, they are indicated by like reference numerals. In this anemometer the stanchion 1 14 includes an elongate channel 45 extending internally along its length and communicating between the recess 1 1 in the mount 10 and the cavity 27 between the deflector 15 and the cap 25. A sunlight sensor (not shown), as for measuring ultraviolet intensity, may be disposed in the cavity 27 enclosed by the cap 25 which may be transparent or include a window therein. The channel 45 is provided to accommodate a cable (not shown) for connecting to the sunlight sensor. The channel 45 intersects with a cable port 46 formed in the mount 10, through which a power/signal conductor 47 exits the mount. The mount 10 is formed of an outer member 1 10 adjacent the deflector 15 fixed to an inner member 210, the members 1 10, 210 cooperating with the sensor plate 12 to enclose the load cell 17 and processing circuit 40. The lip 30 extending about the mouth of the recess in which the sensor plate 12 is received, is formed on the outer member 1 10, with the outer member 1 10 extending around the periphery of the sensor plate 12. The annular space between the outer member 10a and the periphery of the sensor plate 12 allows for water falling on the plate 12 to drain away. To assist in shedding this water, a radiused lip 48 is formed in the member 10a immediately adjacent this annular space, with the outer end of the lip 48 being received in a complementary part of the sensor plate 12. Also for shedding water, the outer face of the cover disc 131 of the sensor plate 12, is convex. Due to its symmetry, the apex 50 of this convex surface lies on the axis 13, but this apex 50 lies generally flush with the plane of the rim 30. In this manner, the gap 24 lies substantially above the rim 30 in this second embodiment, whereas in the first embodiment the gap extended below the plane of the rim 30. In use, the anemometer may be mounted in free air flow and connected by wires, or wirelessly, to a display or a monitoring computer. The deflector 15 is disposed adjacent the sensor plate and aligned so that the tapered surface tapers inwardly towards the sensor plate 12. The deflector 15 may be mounted to the rigid mount 10, or mounted independently. A wind stream in any direction in an incident plane perpendicular to the first axis is deflected by the deflector 15 toward the sensor plate so that a proportion of the flow in the incident plane impinges on the sensor plate 12.

Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope thereof.

Claims

CLAIMS:

1. An anemometer comprising: a rigid mount; a sensor plate mounted for movement relative to the rigid mount, the sensor plate having an outer surface which is substantially symmetrical about a first axis; a load sensor to sense a wind load on the sensor plate; a deflector having a tapered surface with an axis of symmetry substantially coaxial with the first axis, the deflector being disposed adjacent the sensor plate and aligned so that the tapered surface tapers inwardly towards the sensor plate whereby a wind stream in any direction in an incident plane perpendicular to the first axis is deflected toward the sensor plate so that a proportion of the flow in the incident plane impinges on the sensor plate; and receiving and transmitting means configured to receive signals from the load sensor and transmit an output signal indicative of wind speed.

2. The anemometer of claim 1 wherein a gap is provided between the deflector and the outer surface of the sensor plate,

3. The anemometer of claim 1 wherein the deflector is conical, or is a concave conical frustum.

4. The anemometer of claim 3 wherein the surface of the deflector includes an annular peripheral portion and a circular inner portion both lying in respective planes perpendicular to the first axis.

5. The anemometer of claim 4 wherein the annular peripheral portion and a circular inner portion are joined by a concave conical surface and the intersection between the concave conical surface and circular inner portion is radiused to provide a smooth profile.

6. The anemometer of any of the preceding claims wherein the rigid mount includes a recess in which the load sensor is received, and an open mouth which is substantially closed by the sensor plate.

7. The anemometer of claim 6 wherein the sensor plate lies in the recess, or lies entirely within the recess so that no part of the sensor plate projects beyond the boundaries of the rigid mount.

8. The anemometer of claim 7 wherein the outer surface of the sensor plate is convex.

9. The anemometer of any one of claims 6 to 8 wherein the deflector is connected to the rigid mount.

10. The anemometer of claim 9 wherein the deflector is fixedly connected to the rigid mount by a plurality of stanchions angularly equally spaced about the first axis and fixed at a periphery of the deflector.

11. The anemometer of any of the preceding claims wherein the deflector comprises a shell, the anemometer further comprising a cap fixed to the shell to enclose a cavity therein.

12. The anemometer of any of the preceding claims wherein the cap has a convex outer surface which is substantially symmetrical about the first axis.