GB2127972A - Vane anemometers - Google Patents

Abstract

A hand-held electrically operating vane anemometer comprises a casing (3) with a handle (3b) at one end and a cowl (3a) at the other end. A vaned rotor (1) is mounted for free rotation within the cowl (3a). The vanes (2) of the rotor (1) constitute movable electrodes of a capacitance transducer having a fixed capacitor-electrode scanning element (4) mounted on the inside surface of the cowl (3a) adjacent the path of revolution of the tips of the vanes (2). The handle (3b) contains or embodies an electric power source, an integrated electronic circuit assembly (10) connected to the scanning element (4) and a digital read- out screen (7) whereby upon operation of a switch also associated with the handle a reading of the average velocity of air or gas acting on the rotor appears on the screen a few seconds after initially depressing the switch. The circuit assembly may include a microprocessor. <IMAGE>

Description

SPECIFICATION Improvements relating to vane anemometers This invention relates to instruments for measuring air velocity of the kind known as vane anemometers and constitutes a development from the vane anemometer which was described in our British Patent Specification 1157368. That anemometer was adapted to be held in one hand of an operator and comprised a vaned rotor releasably coupled to a rotary digital drum counter. This instrumentwas an exclusively mechanical device requiring no electrical connections or source of power.It has also been mentioned in our patent specification 1445037 that in a vane anemo- meter the vanes of the anemometer rotor can be the movable electrodes of a capacitance type transducer which has a fixed capacitor electrode on the frame of the anemometer adjacent the path of revolution of the tips of the vanes.

The main object of the present invention is to provide a hand held electrically operating vane anemometerwhich is wholly self-contained and which enables average velocity readings of an air or gas stream to be reliably and repeatedly obtained as required.

In accordance with the present invention an instrument ofthe kind referred to, and adapted to be held in the hand, comprises a casing with a handle at one end and a cowl at the other end, a vaned rotor mounted for free rotation within the cowl and of which the vanes constitute movable capacitor electrodes of a capacitance transducer having a fixed capacitor electrode scanning segment mounted on the inside surface of the cowl adjacent the path of revolution of the tips of the vanes, characterised in that the handle contains or embodies an electric power source, an integrated electronic circuit connected to the scanning element and a digital read-out screen whereby upon manual operation of a switch also associated with the handle a reading of the average velocity of air or gas acting on the rotor appears on the screen.

A preferred embodiment of the invention is hereinafter described with reference to the accompanying drawings in which: Fig. lisa front isometric view of the anemometer; Fig. 2 is a fragmentary view of the anemometer rotor cowl to illustrate the shape of an attached scanning segment; Fig. 3 is a central vertical section through the anemometer casing, handle and rotor axis; Fig. 4 is a rear elevation of the anemometer; Fig. 5 is a left side elevation; Fig. 6 is a front elevation; Fig. 7 is a rig ht side elevation; and Fig. 8 is a circuit diagram.

Referring now to the drawings, the anemometer therein shown has a casing 3 moulded from a rigid synthetic plastics material and comprising a rotor cowl 3a and a handle part 3b. Rotatably contained withinthecowl 3a on a shaft which is mounted in twin bearings is a rotor 1 with suitably angled radial vanes.

When the rotor is caused to revolve under the influence of an axially directed stream of air or gas of which the velocity isto be measured the peripheral edge of each such vane 2 in turn acts as a movable electrode of a capacitance transducer which has a fixed electrode in the form of a metal plate or scanning segment 4 which is secured by two screws to the inner surface of the cowl 3a. As shown in Fig. 2 the scanning segment 4 is a metal plate of parallelogram shape so that both parallel edges 5and 6 are setatthe same angle of inclination to the axis of rotation of the rotor 1 as are the peripheral edges of the vanes 2.

Inside the handle there is an electric battery compartment to which access may be obtained by removal of a cover 9. The handle also contains a printed circuit assembly 10 embodying all electrical/ electronic components except the battery and the scanning segment. The printed circuit assembly includes a momentary action on/off switch situated behind a flexible plate 8 on the handle. This plate 8 can easily be deformed by finger orthumb pressure to actuate the switch when a read-out is required on a digital screen 7.

The handle has a removable cover 11 which gives access to the whole contents of the handle. The battery compartment cover 9 is contained within this cover 11 so as to be removable therewith or removable independently as may be desired.

Acircuitdiagram, Fig. 8, depicts the printed circuit assembly 10 which is connected to a battery and the scanning segment 4.

The mode of operation of the instrument is as follows: (a) Place the instrument in the airflow to be measured with the air flowing into the front end and in line with the rotor axis.

(b) Pressthe on/off switch and the instrument will time average countthe airvelocity, the switch remaining depressed.

(c) Aftera preset count period ofafewseconds, the figure of average air velocity will automatically be displayed on the digital read-out screen.

(d) This reading will hold indefinitely whilst the on/off switch is held depressed.

(e) Releasing the switch removes all powertothe circuit.

(f) Further readings may be made by repeating the above procedure.

With reference to the circuit diagram of Figure 8: (a) With the on/off switch in its normally closed position, C1 the timing capacitor is short circuited, and there is no powerto the circuit.

(b) Depressing the on/off switch connects the battery to the input of Svoltregulatorwhich establishes a 5 volt supply to the circuit in about 2 milliseconds.

(c) Once the supply has been established, the capacitor C1 starts charging through the resistor R1.

The reset input to the digital counter is held low, inhibiting the count of input pulses from the capaci tance transducer and holding its register at zero.

(d) After 250ms the capacitor Cl reaches approx The drawing(s) originally filed was/were informal and the print here reproduced is taken from a later filed formal copy.

imately half supply volts and the reset input changes state from low to high no longer inhibiting the input pulse count.

(e) Also as reset input changes to high state, capacitorC2 starts charging through resistor R2.

(f) After a preset period of a few seconds C2 reaches approximately half supply volts, and the store input changes state from low to high, inhibiting any further pulse count.

(g) The registercountremains displayed until power is removed from the circuit by releasing on/off switch.

(h) A buffer stage filters outthe2MHZ carrier frequency, amplifies the signal frequency and feeds the digital counter with a square wave input count.

(i) R3, R4, C3, and T3 provides the display with a decimal point on metric models.

Other developments of the invention will include the addition of a variety of capabilities performed by a microprocessor integral with the electronics circuit within the handle.

Claims (4)

1. An instrument of the kind referred to and adapted to be held in one hand, comprising a casing with a handle atone end and a cowl atthe other end, a vaned rotor mounted for free rotation within the cowl and ofwhich the vanes constitute movable electrode of a capacitance transducer having a fixed capacitorelectrode scanning segment secured to the inside surface of the cowl adjacent the path of revolution of the tips ofthe vanes characterised in that the handle contains or embodies an electric power source, an integrated electronic circuit assembly connected to the scanning element and a digital read-out screen whereby upon operation of a switch also associated with the handle a reading of the average velocity of air or gas acting on the rotor appears on the screen, a few seconds after inititally depressing the switch.

2. An instrument in accordance with Claim 1 in which the scanning element is a plate of parallelogram shape.

3. An instrument in accordance with Claim 1 or 2 in which the electronic circuit assembly incorporates a microprocessor with memory capacity.

4. An instrument of the kind referred to constructed and adapted to operate substantially as hereinbefore described with reference to and as shown in the accompanying drawings.