WO2001055682A1

WO2001055682A1 - Method and equipment for monitoring a supply meter

Info

Publication number: WO2001055682A1
Application number: PCT/DK2001/000046
Authority: WO
Inventors: Peter Malle Andersen
Original assignee: Peter Malle Andersen
Priority date: 2000-01-26
Filing date: 2001-01-22
Publication date: 2001-08-02
Also published as: AU2666001A

Abstract

By a method for monitoring a supply meter part in the meter, a movable indicator is illuminated through a pane and the movement is detected continuously outside the pane by means of reflected light, and an alarm signal is created, preferably when the indicator has not been standing still for a first period of time within a second period of time. The illuminating means and/or light detector means are directional and adjustable. The meter is preferably a water meter and the indicator its star wheel. Equipment for this monitoring has light detector means outside the casing of the meter to detect reflected light, and analytical means to indicate movements of the indicator and to form an alarm signal. Preferably, the equipment has illuminating means to illuminate the indicator, preferably with infrared light. Said means are preferably built together into a scanning unit which is adapted to be fastened on the meter. The scanning unit is preferably adjustable without using tools, and the equipment has preferably a control light to show an output signal from the light detector means.

Description

METHOD AND EQUIPMENT FOR MONITORING A SUPPLY METER

The present invention relates firstly to a method for monitoring an existing supply meter, such as a water meter, where a visible, movable part in the meter is illum- inated through a pane or the like in the meter, and the movement of the part is continuously detected by means of a light being reflected from the part and captured outside the pane, and where a preferably electric signal is created dependent on the movement of the part, by which method no intervention is made in the meter or the pane.

Secondly, the invention relates to a piece of equipment for monitoring a supply meter, such as a water meter, the equipment having illuminating means for illuminating a visible, movable part in the meter, light detecting means for detecting light reflected from the part out through a pane or the like in the meter, and analysis means for detecting movement of the part and for creating a preferably electric signal in the case of such movement, where the illuminating means and light detecting means are meant to be placed outside the casing of the meter without any intervention being required in the meter or the pane.

At present, there is a constantly increasing need for savings of wired resources, such as corporation water, electricity from the mains or gas from a gas distribution network. This requirement can be met, among others, by monitoring the systems of transmission lines in order to detect waste at e.g. defective supplying units, or leakage or drainage .

Therefore, one need among others is to provide a piece of equipment for monitoring the mains or network in order to detect leakage of liquid or gas from the system in question.

During the recent decades of time, much construction has been made with hidden piping arrangement in particular of water pipes. Evidently, it is costly to repair a damage on installations with hidden piping arrangement, however, these installations have an even more important disadvan- tage, i.e. that leakages are very difficult to discover in time.

A late discovery of a leakage because of hidden piping will necessarily increase the extent of the water damage caused by the leakage, which further entails an increase in the already high costs for repair of the damage. The costs and consequent expenses together amounting to 10,000 US$ for a minor leakage are not unusual in installations with hidden piping arrangement. Furthermore, there is a demand for equipment for monitoring a piping system in order to detect waste of liquid or gas from the system in question in case of waste from defective supply units.

As examples of the costs in connection with a water waste in minor, private installations can be mentioned that a toilet cistern running in a way which makes it difficult to discover by looking at the water surface in the toilet bowl, will waste about 100 m³ per year; if the cistern runs such that it can be seen clearly on the water surface, the waste will be about 200 m³ per year. Even a slowly dripping water tap will waste about 10 m³ per year.

With the current water prices, a private water consumer in Western Europe will be prompted to procure a piece of equipment for monitoring his water installation for water waste if such equipment is available on the market.

At today's water price of almost 5 US$ per cubic metre, the costs for simple equipment for registration of such waste will soon pay itself in terms of water conversation. Furthermore, quite many consumers will be interested in preventing waste of resources for general environmental reasons .

Water meters with built-in pulse sensor for remote reading of the consumption are known and marketed. Such a meter is e.g. of the type M-TX from the company Krϋger Cor- rosion A/S, Fabriksparken 50, Glostrup, Denmark. This type is available with nominal diameters from 20 to 50 mm⁰ and a maximal flow from 5 to 30 m³/h. The signal output is an electric contact which can be loaded with 24 V and 0,2 A. Such meters generate impulses which activate a remote counter, whereby the result shown by the meter at any time can be read on the remote counter.

The Swedish patent No. 360,734 discloses thus a water meter with an electric impulse transfer of the rotation of a digit disc. According to this patent, one indicator of the water meter must be dismounted and replaced by a disc which carries a magnet. In the cover glass of the meter, a magnetic switch is integrated and positioned oppo- site said disc. The switch will thus emit one impulse for each rotation of the disc.

The thus modified water meter is suggested to be used for remote transfer of the measuring result .

The British patent application No. 2,051,352 dis- closes a liquid gauge with a transparent housing or a housing with one or two windows. A paddle wheel or a propeller is brought into rotation by the flowing liquid, and the wings of the wheel break or reflect a beam of light which enters and exits the meter through the transparent housing of the meter or its windows. A light source and a light detecting means are built into the meter.

The integration of said parts in these meters can in practice only be made in connection with the production of the meters; the systems are thus unsuitable for retrofitting on existing meters.

Furthermore, the meter disclosed in the Swedish patent No. 360,734 has the disadvantage that a magnet is arranged on an indicator which is driven by the rotor of the meter via a rather low transmission ratio, as the magnetic attraction will then be able to slow down or stop the movement of the meter. Thus, such a meter may have difficulties in obtaining the approval of the utility companies.

The Swedish patent application No. 89 03145-4 discloses an alarm device to be arranged in a detachable manner on a water meter of a generally known type. The alarm device is arranged across the pane of the meter, and a light source in the alarm device illuminates the indicators of the meter by transmitting a beam of light towards the dial of the meter, preferably towards the major part of the dial or the entire dial. One or two light-dependent resistors receive the light which is reflected from the dial and the indicators.

In the application is explained that the "character" of the reflected light is "changed" as soon as one of the indicators moves, and that the "character" of the light is "unchanged" when the indicators stand still. However, there is no indication of which kind of "character" is meant, in which the said changes consist, or any explanation of how any information could be read from the light-dependent resistor.

US patent No. 5,493,917 discloses a method for changing a metering apparatus for remote reading, a metering apparatus for remote reading and a remote reading pick-up for a metering apparatus. The metering apparatus can be a water meter of the dry-running type or another supply meter with an indicator behind a glass.

According to this patent, the glass of the metering apparatus must be replaced by a modified glass in which a pick-up is integrated for detecting the movement of one of the rotating indicators of the metering apparatus. Thus, a counting signal is created each time the indicator in question passes the pick-up. The picking up can be effected by magnetism whereby the pick-up is a reed-contact and the indicator is provided with a permanent magnet, or by light whereby the scanning unit is a photo cell and the indicator is provided with a reflector.

The scanning signal is used for registration (counting) of the consumption. It is preferred to use one of the slowly rotating indicators of the metering apparatus as the registration is only used for distant reading of the metering apparatus in order to state the consumption. By way of example is cited an arrangement providing one impulse per ten gallons of water (37.85 1). It is a disadvantage of the method and the apparatus in said patent that an intervention in the meter is necess- ary in order to mount the pick-up. Since a supply meter will in practice always be sealed, the glass cannot be dismounted without breaking the seal, and the meter cannot thereafter serve as settling basis between supplier and customer before it has been sealed again. In that case, a control would be required that the characteristics of the meter had not been changed by the intervention, and the use of the method and the apparatus on generally known, already installed supply meters must therefore be described as completely unrealis- tic.

Furthermore, the method and apparatus in the patent cannot be used for monitoring a meter in order to detect a leakage as the impulses are much too distributed in time to provide information on small rates of flow. The object of the invention is to provide a method and a piece of equipment for monitoring a supply pattern as it is registered by a supply meter, such that an alarm is given at the presence of a small, continuous supply, which equipment can be retrofitted on a supply meter such as a water meter without any required intervention in the meter and without risk of blocking the meter work.

In the method according to the invention, the object is met in either that the movable part is illuminated by a directional beam of light, the direction of which is adjusted in relation to the position of the movable part, or that the reflected light is captured by a directional detecting means, the direction of which is adjusted in relation to the position of the movable part.

Thus is obtained that the detecting area, i.e. the area of the dial of the meter (behind the glass of the meter) where the detection takes place, can be selected freely, which permits to detect a movement of the very movable part having a desired movement characteristic in relation to the media flow through the meter. Besides, it is thus possible to select a detecting area where the optical contrast is the best possible, e.g. where the movable part, the movement of which is to be detected, has a printed pattern or picture.

In a preferred embodiment, an alarm signal is created when the movable part does not stand still for a first predetermined period of time within a second predetermined period of time.

Thus is obtained that alarm is given at a small, continuous consumption which is typically due to a leakage or drainage in a pipe or an apparatus, as such a consumption consequently results in that the meter is never at a complete standstill.

Preferably, that pointer or indicator which is moving fastest in relation to media flow through the meter is used as the movable part, whereby the leakage is regis- tered faster, and minor leakages can be registered.

In a water meter, it is preferred that the movable part is the star-wheel or indicator wheel of the meter.

Most modern water meters have as their fastest moving, visible part a rotation indicator which often has the form of a star-wheel with teeth along its circumference just as a gearwheel. It is characteristic for such a wheel that it rotates faster than any indicator would do; such a fast rotating indicator would not be readable at all.

Other types of water meters have rotation indicators in the form of indicator wheels which probably rotate just as fast in relation to the media flow as described above, but where the wheel is circular with printed radial lines along the circumference of the wheel or other geometrical figures. The number of such lines can e.g. be 8, 12 or 16. Tests with the invention have proven that such lines are detected in a reliable manner by the method according to the invention.

By detecting the presence or absence of a tooth on such a star-wheel in the detecting area, a detection of the media flow through the meter with an extremely good discrimination is obtained. E X A E

An ordinary household water meter of the type MN QN

2.5 XN EBH from the company Spanner-Pollux GmbH, Ludwigs- hafen (DE) has a capacity of 2.5 m³/h. This meter has a counting gear train for whole cubic metres and four decadic indicators where the most sensitive rotates one revolution per 0.1 1. The indicator wheel in this meter has 20 printed teeth and rotates 33 revolutions per rotation of the most sensitive indicator. A rotation by one tooth of the star- wheel corresponds thus to 0.1/33/20 = 0.00015 1 - 150 μl .

It is obvious that a water meter as the one described will not be able to measure a water quantity with an accuracy of 150 μl, but the example shows clearly that the discrimination of the signal captured by the detecting means is extraordinarily good when the movement of the indicator wheel of the meter is being detected.

The possibility to detect the movement of one single tooth on the indicator wheel is indeed due to the fact that in the present invention, directional and adjustable illuminating means and/or light detecting means are used, which permits a reliable detection of movable objects which are as small as the teeth on the described star-wheel.

This embodiment of the invention where the very movement of the star-wheel or the indicator wheel is detected permits a very reliable and fast detection of dripping taps and similar very small water consumers. With a rougher discrimination, such a small consumer would not succeed in triggering the detecting means of the metering equipment before a new consumption from another water consumer would camouflage the detecting signal from the small consumer completely.

In order to avoid that the general illumination in the room where the meter is mounted does not disturb the registration, it is preferred that on the basis of the reflected light, an electric signal is created and filtered for contents of lower multiples of the mains frequency.

For the same reason, it is preferred to use infrared light, including laser light. In the equipment according to the invention, the said object is met in that the illuminating means are directional and their illumination direction is adjustable in relation to the position of the movable part, or in that the light detecting means are directional and their detection direction are adjustable in relation to the position of the movable part .

Thus is obtained that the detecting area, i.e. the area of the dial of the meter (behind the pane of the meter) where the detecting is effected and which is both illumi- nated by illuminating means and monitored by the light detecting means, can be freely selected, whereby the equipment will detect the movement of exactly that movable part which has a desired movement characteristic in relation to the media flow through the meter. Furthermore, it is obtained that a detecting area can be selected where the optical contrast is the best possible, e.g. where the movable part the movement of which is to be detected has a printed pattern or picture.

It is preferred to use infrared light which will entail that the equipment will be insensitive to extraneous light and changes in the general illumination.

The light detecting means - and preferably also the illuminating means - have preferably an optical filter for filtering of the light which is reflected to the light det- ecting means whereby disturbance from extraneous light can be further minimised.

Analysis means in the equipment comprise preferably means for creating an alarm signal on the basis of the temporal behaviour of an output signal from the light detecting means, such that the consumer is made aware of a continuous consumption. The alarm signal can in a manner known per se control sound or light signalling devices.

It is preferred that the analysis means comprise electric filters for filtering an output signal from the light detecting means, preferably band stop filters which are tuned to lower multiples of the mains frequency.

Thus is obtained that the general illumination in the room where the meter is mounted will not disturb the registration. It is preferred that the equipment has an indicator such as a control light to display an output signal from the light detecting means.

It is thus obtained that the output signal can be monitored while the equipment is being mounted on the meter such that the scanning process can be closely followed during mounting. The user is thus ensured the possibility to adjust the scanning unit in the best possible way.

Furthermore the possibility is obtained for a general monitoring of the movement pattern of the supply meter. Such a monitoring with the human eye can often deduce information to which a preprogrammed alarm will not be able to react .

In a particularly preferred embodiment, the detecting field of the scanning unit is 30-60 mm², preferably 40-50 mm² at a distance of 18 mm, corresponding to a detecting angle of 2 x 12.5°, such that as big a portion as practically possible of the detecting field is occupied by the outline of the movable part in order to obtain a more reliable detection. In a second particularly preferred embodiment, the light detecting means and illuminating means are built together as a scanning unit which is preferably adapted to be fastened on the meter by means of a clamping device . In this way, a simple, clear, secure and less expensive posi- tion is obtained of both the illuminating means and light detecting means. The scanning unit is preferably suspended such that its position and direction in relation to the meter are adjustable without the use of tools. A consumer may thus himself adjust the scanning unit to scan the movable part in question of the meter.

The scanning unit has preferably an indicator such as a control light to display an output signal from the light detecting means.

Thus is obtained that the output signal can be mon- itored already while the scanning unit is being mounted on the meter such that the process and merit of the scanning can be followed closely during the mounting. The user is thus ensured the possibility to adjust the scanning unit in the best possible way. The scanning unit can be designed with a waterproof casing, whereby it can be mounted on a water meter placed in a well or in a similar wet or humid environment.

Finally, it is preferred that the scanning unit and the associated connection cable are waterproof. The scanning can thus be mounted on a water meter placed in a well, whether there is water in the well or not, and whether the meter is positioned above or below the water surface, if any.

In the following, the invention will be explained in more detail by means of embodiment examples with reference to the schematic drawing, in which

Fig. 1 shows a longitudinal section-in-part in a water meter of a generally known type, on which a scanning unit according to the invention is mounted, Fig. 2 shows the scanning unit in Fig. 1 in a longitudinal section,

Fig. 3 shows the dial in the water meter in Fig. 1, and

Fig. 4 shows a block diagram of a piece of equipment according to the invention. The same reference designation refers to the same element in all the figures.

Fig. 1 shows a water meter 1 of a generally known type. The top portion of the meter 1 with the glass 2 is shown in longitudinal section, and the cover 3 is opened so that there is free access to the top side of the glass

2.

Under the glass 2, a dial 4 is arranged, as shown in Fig. 3. The dial 4 is provided with a counting gear train 31 which in the shown meter counts whole cubic metres. Furthermore, there are three indicators, i.e. an indicator 32 counting the number of hundred litres, an indicator 33 counting the number of ten litres and an indicator 34 counting the number of litres. Finally, there is a star-wheel 6 which is arranged on a fast rotating axle in the meter work.

The star-wheel rotates thus considerably faster than the litre indicator 34 when the meter is working. In order to improve the readability, the star-wheel is in the shown meter provided with teeth 35 along the edge and an eccentrically arranged marking.

There are known water meters which instead of a star-wheel with teeth has a circular dial with printed radial lines along the edge or other figures such as a spi- ral.

The object of all these visual indicators is to constitute a conspicuous and easily readable indicator of water consumption. Such indicators have by and large always figures or symbols which are designed with a highly optical contrast in order to facilitate the reading.

Fig. 1 shows two indicators 5 and the star-wheel

6 above the dial 4. The indicators are placed on shafts 7 and the star-wheel is placed on a shaft 8. The shafts are driven in a generally known manner from the not-shown meter- ing work in the interior of the meter. A scanning unit 9 according to the invention is fastened to the meter in such a position that the head 10 of the scanning unit with a not -shown window points towards the edge of the star-wheel 6 of the water meter 1. According to the invention, the scanning unit 9 is adjusted such that it "watches" the teeth of the star-wheel. This adjustment is essential for the good and secure function of the equipment according to the invention and for the possibility to use the equipment on many different types of and embodiments of supply meters and similar apparatus with visually readable indicators.

The scanning unit 9 is shown in a longitudinal section in Fig. 2. The scanning unit 9 has a housing 28 in which a printed circuit board 23 is mounted. Two of the components mounted on the printed circuit board are shown in Fig. 2, i.e. a photo cell 21 and a light-emitting diode 11. Furthermore, a cable 12 (which is only seen in Fig. 1) is connected to the printed circuit board in order to provide this with power and control signals and to carry away metering signals.

The photo cell 21 which can be e.g. of the type OPB608B from the company Optek Technology, Inc., 1215 Crosby Road, Carrollton, Texas (US) , contains in the shown embodiment a light-emitting diode 25 which emits infrared light 29, and an NPN silicon photo-transistor 26 which is sensitive to light 30 from the light-emitting diode 25.

By the intended use of the photo cell, the light 29 is reflected from the light-emitting diode 25 by a reflecting object 27 in the form of reflected light 30 to the photo-transistor which thus emits a signal. This signal is thus an indication of the presence of a reflecting object 27.

Both the light-emitting diode and the photo-transistor "watch" through the same surface of the casing of the photo cell, and a reflecting object placed opposite this surface will thus reflect the light of the light-emitting diode back into the photo-transistor which will then react.

With this photo cell, a detecting angle of 2 x 12.5° is obtained in practice, where 12.5° is half the top angle in a conical surface with the apex near said surface of the photo cell. In this way, light reflecting objects within this conical surface entail that the photo cell reacts, whereas light reflecting objects outside the conical surface will not make the photo cell react. Depending on the conditions, according to the invention, photo cells can be selected with a more or less narrow vertical angle in said conical surface, whereby the detecting area which is in practice obtained on the indicator and its surroundings will be smaller or larger, respectively. A smaller detecting area can provide the light detecting means with a better discrimination because the photo cell in practice may only "watch" one tooth at a time on the star-wheel, however, it may be difficult to adjust the direction because this must be done in a correspondingly pre- cise manner.

Vice versa , a larger detecting area will entail a less critical directional adjustment, probably also a minor discrimination, because the light quantity incident to the photo-transistor will be integrated over a larger area of the indicator of the supply meter so that the photo cell might have difficulties in distinguishing the individual teeth on a star-wheel.

In front of the photo cell 21, an optical filter 24 is positioned and permits only infrared light with a desired wavelength to pass such that a disturbing influence from surrounding light or heat radiation is reduced to a minimum.

A very secure detection is thus obtained. Tests have proven that when using infrared light together with said filter, a reliable detection in both powerful general lightning and total darkness is obtained. For usage in connection with a water meter, the scanning unit is preferably waterproof. Water meters can in many case be installed in humid or wet surroundings, e.g. in wells, and in several cases, the meter is actually placed under water or can be submerged regularly.

When the scanning unit 9 and the cable 12 with the bush 22 are made impermeable to a moderate static water pressure, the scanning unit can without any problem be mounted in wet surroundings or under water. The watertightness can be provided in any way suitable, however, according to the invention, preferably in the way that the housing 28 and the bush 22 are cast or filled with an appropriate plastic material, such as a two-component epoxy.

In Fig. 1, the scanning unit 9 is mounted such that the light 29 is reflected from the teeth 35 of the star-wheel 6 (cf. Fig. 3). The photo-transistor 26 will thus emit an impulse each time one of the teeth 35 passes through the "visual field" of the photo cell 21. A pulse train from the exit of the photo-transistor 26 with a certain frequency shows in this way that the star-wheel 6 rotates with a certain number of revolutions.

The person skilled in the art will realise that other movable and optically readable indicators, such as the above described wheels with applied lines or figures, are readable in a likewise simple and secure way by means of a scanning unit such as the one described (9) .

The scanning unit 9 is in Fig. 1 mounted on the meter 1 by means of a flexible arm 14 carried by a foot 15 fastened to the meter 1 in a suitable place by means of a clip or the like 16. The arm 14 has a retainer 13 carrying the scanning unit 9 ,

The illustrated fastening is only to be understood as an example; the scanning unit 9 can be fastened on the meter 1 in any suitable way. Preferably a fastening is used which can be made without using any tools and without particular skills being required for the mounting. E.g. the scanning unit can be adhered on the glass 2 by a piece of double adhesive foam tape.

As stated above, it is, however, essential that the scanning unit 9 is adjustable relative to the supply meter 1. In the shown embodiment, this is obtained in that the arm 14 is made of metal which on one side is sufficiently rigid for the scanning unit 9 to be carried in a stable and secure manner, and on the other side is sufficiently flexible for the direction of the scanning unit towards the star-wheel - and the distance of the unit from the glass 2 - to be adjusted in a simple and secure manner without using tools, merely by bending the arm 14 appropriately.

The resulting sensitivity and the degree of discrimination of the scanning unit 9 in relation the indic- ator of the present supply meter are the ones to be adjusted for satisfactory values.

In this connection, it need not be both the direction and position of the light-emitting diode 25 and the photo-transistor which are adjusted. In the embodiments where the illuminating means (25) (the light source) and the light detecting means (26) form independent units, it is according to the invention sufficient that one of these units is adjustable in the direction and preferably also the position (the distance from the supply meter) . Combinations may thus be used with a fixed illuminating means with a wide illumination field and an adjustable light detecting means with a narrow detection field, or an adjustable illuminating means with a narrow illumination field and a fixed light detecting means with a wide detec- tion field.

Fig. 4 shows block diagrams of the electronic circuits in the scanning unit 9. The output signal from the photo-transistor is carried (42) via a band stop filter 43 to a comparator 44 which serves as a discriminator in order to provide an enhanced and unambiguous output signal on the wire 45. This output signal is in the shown embodi- ment a digital signal which has one level when much light is reflected from the light-emitting diode 25 to the photo- transistor 26, and another level when little light is reflected from the light-emitting diode 25 to the photo- transistor 26.

The band stop filter 43 is adjusted to the frequency of the mains or can be adapted to block signals with frequencies corresponding to the lower harmonics of the mains frequency. The use of this filter has by tests proved to entail a heavy reduction of the sensitivity of the detecting means to extraneous light signals containing the frequency of the mains, such as illumination with a fluorescent tube. Thus is obtained a more secure detection of the movement of the star-wheel . The output signal is carried to an amplifier 46 which drives a light-emitting diode 11. The light-emitting diode 11 is positioned in a visible place on the top face of the scanning unit 9, cf . Figs. 1-2. It can thus be directly observed whether light is reflected from the star- wheel 6 to the photo cell 21 or not. The adjustment of the direction of the scanning unit towards the teeth of the star-wheel is in this way facilitated to a considerable extent .

The output signal from the comparator 45 is fur- ther carried via the cable 12 from the scanning unit to a control unit 41, cf. Fig. 4. The control unit 41 is arranged in a housing at a place which is convenient for the user and which can be situated near to or far from the water meter 1; the length of the cable 12 is adjusted accord- ingly.

In the control unit 41, the signal is carried from the scanning unit 9 to a so-called one-shot 47 (mono- stable multivibrator) , which retains its output signal in e.g. 2 sees after having been triggered. Thus is obtained a stable signal with a desired logical level on the output of the one-shot 47 as long as the scanning unit emits pulses even though the pulses necessarily keep changing their logical level .

The output signal from the one-shot 47 is carried to a delay circuit 48, on the output 49 of which a signal does not occur until a signal has been present on the input without interruption for a certain period of time, e.g. 5 min.

The effect of the circuits 47 and 48 is then e.g. that a signal is present on the node 49 if the star-wheel of the meter 1 has not been stopped for at least 2 s within a period of 5 min.

A signal on the node 49 is thus a sign indicating a continuous consumption of e.g. water, which could be due to leakage or another system error. The signal on the node 49 is carried to a lamp amplifier 50 which turns on a warning lamp 51; to an alarm amplifier 52 which drives the loudspeaker 53 the loudness of which can be adjusted by a potentiometer 54; and to a relay amplifier 55 which drives a relay 56, from the contacts 57 of which an alarm signal can be had to an external signal receiver such as a central alarm system.

In the present embodiment, the delay time of the delay circuit 48 can be adjusted by means of an adjustment means such as a switch 58; thus, the function of the equip- ment can be adapted to different conditions of use.

Preferably, a not shown control light corresponding to the light -emitting diode 11 is arranged on the control unit 41 - or a separate housing - and is driven by the output signal from the scanning unit via an amplifier cor- responding to the amplifier 46. Thus, said control light can be arranged in a place where it can be monitored continuously or often by staff, and in this way, all "visible" variations in the behaviour of the supply meter can be registered visually. It is often possibly by the human eye to observe special patterns in the flashing signals from a control light which automatic equipment is not able to decipher .

Even though the invention in the preceding has been explained in detail with reference to a water meter, nothing prevents, as stated, the invention from being used with any other supply meter with a movable indicator behind a glass pane .

As examples of such meters can be mentioned heat counters for district heating, gas meters, oleometers and electricity meters and meters in general for liquids, gases or electric power.

Besides, the invention can be used in other cases where the movement of a pointer or another visible indicator has to be monitored.

Claims

P A T E N T C L A I M S

1. A method for monitoring an existing supply meter such as a water meter, where a visible, movable part in the meter is illuminated through a pane or the like in the meter, and the movement of the part is continuously being detected by means of light being reflected from said part and captured outside the pane, and where a preferably electric signal is created dependent on the movement of said part, by which method no intervention is made in the meter or the pane, c h a r a c t e r i s e d in that said movable part is illuminated by a directional beam of light, the direction of which is adjusted relative to the position of said movable part .

2. A method for monitoring an existing supply meter, such as a water meter, where a visible, movable part in the meter is illuminated through a pane or the like in the meter, and the movements of the part is continuously being detected by means of light being reflected from said part and captured outside the pane, and where a preferably elec- trie signal is created dependent on the movement of said part, by which method no intervention is made in the meter or the pane, c h a r a c t e r i s e d in that the reflected light is captured by a directional detecting means, the direction of which is adjusted relative to the position of said movable part.

3. A method according to claim 1 or 2 , c h a r a c t e r i s e d in that an alarm signal is created when the movable part does not stand still for a first predetermined period of time within a second predetermined period of time.

4. A method according to any of the preceding claims, c h a r a c t e r i s e d in that the movable part is that pointer or indicator on the meter which moves fastest relative to the media flow through the meter.

5. A method according to any of the preceding claims, c h a r a c t e r i s e d in that the meter is a water meter, and that the movable part is the star-wheel or indicator wheel of the meter.

6. A method according to any of the preceding claims, c h a r a c t e r i s e d in that on the basis of the reflected light, an electric signal is created and filtered for contents of lower multiples of the mains frequency.

7. A method according to any of the preceding claims, c h a r a c t e r i s e d in that the light is infrared light.

8. Equipment for monitoring of a supply meter, such as a water meter, which equipment has illuminating means for illuminating a visible, movable part in the meter, light detecting means for detecting light reflected from said part out through a pane or alike in the meter, and analysis means for detecting movement of said part and for creating a preferably electric signal in case of such movement, where the illuminating means and light detecting means are adapted to be placed outside the casing of the meter without any intervention being required in the meter or the pane, c h a r a c t e r i s e d in that the illuminating means are directional and that their illumination direction is adjustable relative to the position of said movable part.

9. Equipment for monitoring of a supply meter, such as a water meter, which equipment has illuminating means for illuminating a visible, movable part in the meter, light detecting means for detecting light reflected from said part out through a pane or alike in the meter, and analysis means for detecting movement of said part and for creating a preferably electric signal in case of such movement, where the illuminating means and light detecting means are adapted to be placed outside the casing of the meter without any inter- vention being required in the meter or the pane, c h a r a c t e r i s e d in that the light detecting means are directional and that their detection direction is adjustable relative to the position of said movable part.

10. Equipment according to claim 8 or 9, c h a r a c t e r i s e d in that the light is infrared light.

11. Equipment according to any of the claims 8-10, c h a r a c t e r i s e d in comprising an optical filter for filtering the light reflected to the light detecting means .

12. Equipment according to any of the claims 8-11, c h a r a c t e r i s e d in that the analysis means comprise means for creating an alarm signal on the basis of the time-related behaviour of an output signal from the light detecting means.

13. Equipment according to any of the claims 8-12, c h a r a c t e r i s e d in that the analysis means comprise electric filters for filtering an output signal from light detecting means, preferably band stop filters which are tuned to lower multiples of the mains frequency.

14. Equipment according to any of the claims 8-13, c h a r a c t e r i s e d in that the equipment has an indicator, such as a control light, to display an output signal from light detecting means.

15. Equipment according to any of the claims 8-14, c h a r a c t e r i s e d in that the detection field of the light detecting means is 20-80 mm², preferably 40-50 mm², at a distance of 18 mm.

16. Equipment according to any of the claims 8-15, c h a r a c t e r i s e d in that the light detecting means and the illuminating means are built together as a scanning unit which is preferably adapted to be fastened on the meter by means of a clamping device .

17. Equipment according to claim 16, c h a r a c t e r i s e d in that the scanning unit is suspended in such way that its position and direction relative to the meter can be adjusted without the use of tools.

18. Equipment according to claim 16 or 17, c h a r a c t e r i s e d in that the scanning unit has an indicator such as a control light to display an output signal from the light detecting means.

19. Equipment according to any of the claims 16-18, c h a r a c t e r i s e d in that the scanning unit has a waterproof housing.

20. Equipment according to any of the claims 16-19, c h a r a c t e r i s e d in that the scanning unit is designed so that it is impermeable against static water pressure, preferably by being cast or filled with a plastic material .