GB2433114A

GB2433114A - A float trasducer

Info

Publication number: GB2433114A
Application number: GB0525117A
Authority: GB
Inventors: Kim Peter Hastings; Christopher John Cathles
Original assignee: VALIDATION CT
Current assignee: VALIDATION CT
Priority date: 2005-12-12
Filing date: 2005-12-12
Publication date: 2007-06-13
Anticipated expiration: 2025-12-12
Also published as: GB2433114B; GB0525117D0; EP1960745A1; WO2007068889A1

Abstract

The invention provides apparatus for detecting the position of a float in a flow or level meter, comprising a series of transceivers (paired transmitters and receivers, such as LEDs and phototransistors) disposed along a selected range of the float's intended operating movement. Selected transceivers have their transmitter or receiver oriented out of functional alignment with the corresponding receiver or transmitter of the adjacent transceivers to provide immunity from cross-talk between adjacent transceivers. A helical arrangement is suggested. Variants of the device use infra-red transceivers to provide immunity from incident visible light. Several receivers may correspond to a single transmitter.

Description

A Float Transducer

Field of the Invention

The invention relates to apparatus for detecting the position of a float in a flow or level meter.

Background and Prior Art Known to the Applicant

Liquid or gas flow meters in which the fluid flow rate is indicated by displacement of a ball or a float in a vertical tube resulting from the fluid flow, are known. Typically, such meters comprise an elongate tube with a tapered bore. The tube is mounted vertically with the narrower end of the bore pointing downwards. The float, often in the form of a small ball is located within the tapered tube. Fluid is passed through the tube, from bottom to top, which causes the bal] to rise up the tube to an equilibrium position, related to the flow rate.

In other embodiments, the ball-type float is replaced by a more sophisticated float, having fins, or spirally-orientated grooves to cause the float to spin as it is suspended in the fluid.

This affords greater stability to the float.

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* S S * S S S S * . . S S S S *5 S * S S S S S S S S * S* * S* S.. S * S 555 * in either case, the flow meter tube is often constructed of plastic, glass or other see-through material to enable the float position to be read manually against an adjacent scale, calibrated to indicate flow rate for a given fluid.

A similar type of arrangement is often used on level meters, to indicate eg the level of liquid in a tank. A vertically extending tube is placed in fluid communication with the contents of the tank, and a ball, or other float, is placed within the tube to float on the surface of the liquid. As the liquid level rises or falls, the ball is carried with it. The level of liquid in the tank may thus he readily determined by noting the position of the ball with respect to a suitable, adjacent scale.

Such flow meters and level meters are in widespread use in many industries. As industrial processes are automated, it is often required to implement a remote-sensing regime where information on fluid flow, or liquid level, can be transmitted to a computer system for control or monitoring purposes. Float position sensors have been designed that can be clipped onto the outside of the flow meter or level meter tube. Typically these consist of one or two pairs of optical transmitter-receiver elements that can be positioned on a tube to indicate the presence of the float at the extremities of the tube. These are typically used for indicating an alarm condition when the flow rate or level exceeds, or falls below, a pre-determined value. Whilst these devices are capable of indicating the presence or absence of a float at a particular position in a flow or level meter, they are not suitable for sensing the float position in all locations. For example, as soon as the float ceases to interrupt the transmitter-receiver signal, no information is available as to the float position; the float could be above or below the transceiver and the same signal would result.

The applicant's initial approach to solving this problem was to mount a number of such transceiver elements, side by side, along the length of the fluid meter tube, with the expectation that this would provide an effective system to signal the position of the float at any location within the tube. 1-lowever, they have found a number of new problems that arise from this attempted conflguration.

* * .** S.. * *SS * S * S S S S * * S S * S * S SS S S S S S * S S S S S 55 5 ** 5** 5 * S 555 * Firstly, if the transceiving elements are placed as close together as they need to be to provide accurate positioning information, with relatively high resolution, then the transmitting element from one transceiver can trigger the receiving element of adjacent transceivers. Where, for example, the transceivers comprise a light emitting diode (LED) paired with a phototransistor, light from one LED can illuminate the phototransistor of adjacent transceivers. Therefore, situations can arise where the float never casts a shadow on a phototransistor and the ability to detect the float is therefore lost.

Secondly, floats that are commonly used in these devices are often made of metal, in the form of ball bearings. The reflective nature of the surface of these floats can lead to light bouncing around the tube giving false signals from the transceivers.

It is an object of the present invention to attempt a solution to these and other problems.

Summary of the invention

Accordingly, the invention provides apparatus for detecting the position of a float (as defined herein) in a flow or level meter, of the kind (known per Se) in which a plurality of transceivers, each transceiver comprising a transmitting element and a receiving element, is disposed along a selected range of the float's intended operating movement with the intention that at any one position within that range, a given transceiver will register the float's position; characterised by the feature that selected ones of said transceivers have their transmitter or receiver orientated out of functional alignment with the corresponding receiver or transmitter of the adjacent transceivers.

In this way, transmitters are unable to erroneously trigger a response in an adjacent receiver.

Preferably, one or more receiving element comprises a plurality of adjacent receiving units. in a particularly preferred embodiment, one or more transceiver comprises three receiving units and a transmitting unit. For example, a receiving element could comprise three receiving units, each being a phototransistor. and the transmitting unit could be a light emitting diode (LED). The applicants have found that this configuration is * * **. S.. * *iS * . * . . S S * * S S S S S S 5 5 a s * * S S S * S 55 5 ** S.. * * S *s.

particularly immune to the erroneous signals described above. Furthermore, signals from each of the receiving units may be used, with appropriate logic that will be evident to the skilled addressee, to provide a "voting" algorithm to further enhance the robustness of the sensing system.

in a more preferable aspect of the invention, the transmitter or receiver of every alternate transceiver is oriented out of functional alignment with the corresponding receiver or transmitter of the adjacent transceivers. In this way, the robust signal transduction occurs along the whole length of the flow meter tube.

in any arrangement of the apparatus, it is preferable that selected ones of said transceivers have their transmitter or receiver oriented out of alignment by substantially 180 degrees.

This configuration gives maximum immunity from signal cross-talk from adjacent transceiver units, and has the added benefit that alternate receiving and transmitting units can be mounted adjacent to each other, e.g. mounted on the same circuit board, thus making a more compact unit.

Also in any aspect of the invention, it is preferable that at least one transceiver comprises an infrared transmitter and receiver. The applicants have found that if optical LEDs and phototransistors are used, direct sunlight falling into the device can, in some circumstances, trigger erroneous readings. The use of infrared signals effectively solves this problem.

Included within the scope of the invention is apparatus for detecting the position of the float (as defined herein) in a flow or level meter substantially as described herein, with reference to, and as illustrated by, any appropriate combination of the accompanying drawings.

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Brief Description of the Drawings

The invention will be described with reference to the accompanying drawings, in which; Figure 1 is a schematic diagram of a float sensor for a level meter comprising closely spaced adjacent transceivers; Figure 2 is a schematic diagram of a float sensor for a flow meter with adjacent transceiving units out of functional alignment; Figure 3 is a schematic diagram of a float sensor for a flow or level meter where transceiving units comprise a plurality of receivers; Figure 4 illustrates a series of adjacent transceivers out of functional alignment with their neighbours; Figure 5 shows a series of adjacent transceivers, out of alignment by 180 degrees.

Description of the Preferred Embodiments

Figure 1 illustrates, schematically, apparatus, generally indicated by 1 according to the present invention for use in detecting the float position in eg a flow meter. The flow meter comprises a tapered tube 2 and a float 3. Disposed along the length of the tube 2 are a number of transmitters 4, and corresponding receivers 5. To illustrate the problem identified by the inventors, a situation is shown where the float is in a position such that it should interrupt the transmitted beam from transmitter 4b to receiver 5b. However, when the transceiving elements are close enough to provide the required resolution, a transmitted signal (eg light) from transmitter 4a can illuminate receiver 5b. Similarly, light from transmitter 4c can illuminate receiver 5b. In this case, none of the receiving elements would detect the position of the float. it is the finding of this problem that has led the applicant to the present invention.

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* I 4e I Figure 2 illustrates apparatus according to the present invention, whereby a series of transceiving units 6 is disposed along the length of the tube 2, with adjacent transceivers 6 out of functional alignment with their neighbours. Figure 2 (b) illustrates, for clarity, a transceiver 6, comprising a single transmitter 4 and a single receiver 5. The paired transmitter (T) and receivcr (R) units constitute, in this embodiment, the transceivers; only one such pair in figure 2 (a) is illustrated with a bounding box, for sake of clarity. Figure 2 (a) shows a plurality of such transceivers 6 arranged along the length of a flow meter tubc. With the float 3 in the position indicated, light from transmitter 4f is blocked from reaching receiver 5f, thus providing a signal. As the neighbouring transmitters (4e and 4g) are out of functional alignment using this configuration, light from transmitter 4d is unable to erroneously illuminate receiver 5e. Similarly, light from transmitter 4h is unable to erroneously illuminate the receiver Se. Thus, the system is immune from the problems encountered in the configuration illustrated in figure 1.

By "functional alignment" we mean that the operating signal from the transmitter element of one transceiver is unable to trigger the receiving element of an adjacent transceiver.

Where LEDs are used as transmitters, light is directed typically within +7-30 degrees of the main axis of the LED (indicated by the arrows in Figures 2 aM 3). Given the beam angle of transmitters, and the sensitivity characteristics of the receivers, an appropriate spacing of transceiver elements may be readily selected, given the dimensions of the flow-or level meter tube on which the device is to be used. If it is required that the transceiver elements are closer together (eg to obtain a higher resolution) then a more focused signal beam may be used, eg by use of a collimator.

Figure 3 illustrates a particularly preferred embodiment of the invention where each transceiver 6 comprises three receivers 5 and a transmitter 4. A single such transceiver 6 is illustrated, for clarity, in figure 3 (b). Figure 3 (a) illustrates a plurality of such transceivers 6 arranged along a flow meter tube 2. It can be seen that, for example, the transmitter in transceiver unit 6a is out of functional alignment with the receiving elements of transceiver 6b, and is sufficiently far along the length of the tube as to be unable to crroneousiy illuminate any of the receiving elements in transceiver 6c. As discussed above, the use of a plurality (in this case, three) of receiving units allows a a a Id aI * ** a. * * * a. * * a a * I a a a S I a. * a *i ssS I I$ voting system to be implemented, if required, to further improve the robustness, and accuracy, of the sensing system.

Figure 4 illustrates an embodiment of the invention whereby a series of transceiving units 6 is arranged in a spiral fashion around a flow-or level meter tube such that adjacent transceivers 6 are out of functional alignment with their neighbouring transceivers.

Figure 5 illustrates a particularly preferred embodiment wherein the transceivers 6 are out of alignment by substantially 180 degrees with respect to the neighbouring transceivers.

In this way, adjacent receiving and transmitting elements may be mounted closely together, eg on the same circuit board, leading to a more compact unit. e. *.* *

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Claims

CLAIMS

I. Apparatus for detecting the position of a float (as defined herein) in a flow or level meter, of the kind (kiiown per se) in which a plurality of transceivers, each transceiver comprising a transmitting element and a receiving element, is disposed along a selected range of the float's intended operating movement with the intention that at any one position within that range, a given transceiver will register the float's position; characterised by the feature that selected ones of said transceivers have their transmitter or receiver oriented out of functional alignment with the corresponding receiver or transmitter of the adjacent transceivers.

2. Apparatus according to claim I wherein one or more receiving element comprises a plurality of adjacent receiving units.

3. Apparatus according to claim 2 wherein one or more transceiver comprises three receiving units and a transmitting unit.

4. Apparatus according to any preceding claim wherein the transmitter or receiver of every alternate transceiver is oriented out of functional alignment with the corresponding receiver or transmitter of the adjacent transceivers.

5. Apparatus according to any preceding claim wherein selected ones of said transceivers have their transmitter or receiver oriented out of alignment by substantially 1 80 degrees.

6. Apparatus according to any preceding claim wherein at least one transceiver comprises an infra-red transmitter and receiver.

7. Apparatus for detecting the position of a float (as defined herein) in a flow or level meter substantially as described herein, with reference to, and as illustrated by, any appropriate combination of the accompanying drawings.

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1*1 * S. S * * S * * a * : * S.. * : * :. *SI i%menaments to the claims have been filed as follows 1. Apparatus fbr detecting the position of a float a flow or level meter, of the kind (known per se) in which a plurality of transceivers, each transceiver comprising a transmuting element and a receiving element, is disposed along a selected range of the float's intcndcd operating movement with the intention that at any one position within that range, a given transceiver will register the float's position; charactcrised by the feature that selected onbs of said transceivers have their transmitter or receiver oriented out of functional alignment with the corresponding receiver or transmitter olihe adjacent transceivers.

2. Apparatus according to claim I wherein one or more receiving element comprises a plurality of adjacent receiving units. S... S...

3. Apparatus according to claim 2 wherein one or more transceiver comprises three * receiving units and a transmitting unit.

* S *** I 4. Apparatus according to any preceding claim wherein the transmitter or receiver of * .: every alternate transceiver is oriented out of functional alignment with the corresponding . 20 receiver or transmitter of the adjacent transceivers.

5. Apparatus aCCOr(liflg to any preceding claim wherein selected ones of said transceivers have their transmitter or receiver oriented out of alignment by substantially 180 degrees.

6. Apparatus according to any preceding claim wherein at least one transceiver comprises an in fra-red transmitter and receiver.

7. Apparatus for detecting the position of a floatdi d-liin a flow or level meter substantially as described herein, with reference to, and as illustrated by, any appropriate combinati on of the accompanying drawings.