A SENSOR FOR OPTICAL DETECTION OF THE MOVABLE PART OF A CONSUMPTION METER FOR VISUAL INDICATION OF THE CONSUMPTION

Abstract: A sensor for optical detection of the moving parts (13) of a consumption meter (11) for visual indication of consumption has visual aiming means (16) assisting the correct mounting of the sensor with respect to the movable parts (13) of the meter. For use in connection with an electricity meter (11), which has a circular disc (13) with a visible mark (14) on its periphery, the aiming means (16) are designed so as to have an extent in two dimensions and so as to define a plane which is caused to coincide with the rotating disc (13) of the electricity meter (11) at the mounting of the sensor on the meter.

Description: A SENSOR FOR OPTICAL DETECTION OF THE MOVABLE PART OF A CONSUMPTION METER FOR VISUAL INDICATION OF THE CONSUMPTION, The invention concerns a sensor for optical detection of the movable parts of a consumption meter for visual indi¬ cation of the consumption and comprising aiming means assisting the mounting of the sensor on the consumption meter. Electricity, water or gas meters traditionally have a mechanical counter for indication of accumulated consump¬ tion and moreover often a disc or a pointer rotating at a rate which is proportional to the size of the instan¬ taneous consumption. These movable parts, which indicate consumption, are visible from the outside and can be ob¬ served through a transparent plate of glass or the like, which forms part of the meter casing protecting against unauthorized manipulation with the meter. The known sensors have optically detecting elements and are adapted for external mounting on the meter in a manner such that the optically detecting elements "see" the consumption indicating parts of the meter, and when these parts move passed the "visual field" of the detecting parts, signals indicating such passage are formed on the electric output of these parts. This output signal can be applied to an electronic computing circuit which e.g. converts the re¬ ceived signals to accumulated consumption, performs sta¬ tistical calculations such as the distribution of the consumption over various periods of time, metered consump- tion converted to costs, ect. Such sensors allow external optical detection of the movable parts of a consumption meter without unauthorized manipulation with the meter. GB 2 179 399 describes a sensor of the present type, and where the aiming means are formed by an edge on a plate. Consumption meters frequently have a metal casing, and their consumption indicating, rotating disc is thus posi¬ tioned partly in the dark so that just its periphery is visible. Aiming transversely to the edge is performed when mounting the sensor on the consumption meter, and the sen¬ sor is mounted so that the edge will be seen to coincide with the periphery of the rotating disc on the consumption meter. The aiming edge does not define any aiming plane, and aiming errors can therefore easily occur unless by chance the eye is in the plane of the rotating disc. When the known sensors are to be mounted on a consumption meter, it requires much care to have the sensor mounted correctly with respect to the parts whose movement the sensor is to detect, and frequently the user cannot check whether the sensor is mounted correctly or optimally. At worst the sensor will not detect any movement at all, while intermittent error function will occur in other cases. The object of the invention is to provide a sensor of the present type, which obviates these problems, and which can be mounted correctly on the meter with respect to its con¬ sumption indicating parts in a simple and safe manner. This object is achieved by designing the aiming means of the sensor such that they define a visual angle around an aiming plane, as stated in claim 1. Expedient embodiments of the invention are defined in the other patent claims. The invention will be explained more fully below with reference to the drawing, in which fig. 1 shows a preferred sensor according to the invention at its mounting on a consumption meter as well as an asso¬ ciated central unit with calculating facilities, fig. 2 is a perspective view of the sensor of fig. 1, fig. 3 shows the detection principle for the sensor ac¬ cording to the invention, fig. 4 shows the principle for the mounting of the sensor by means of the aiming means according to the invention, figs. 5, 6 and 7 show the preferred embodiment of the in¬ vention in various projections, and figs. 8-12 show alternative embodiments of the aiming means according to the invention. Fig. 1 shows an electricity meter 11 with a transparent panel 12 through which the circular disc 13 of the elec¬ tricity meter is visible. Fig. 4 shows how the disc 13 of the meter is mounted on a vertical shaft 21, and when electric energy is consumed, the shaft 21 with the disc 13 rotates at a rate proportional to the size of the in- stantaneous consumption of electric power. At its periphe¬ ral edge the disc 13 is provided with a mark 14, which is typically painted in a colour different from the rest of the disc, but in this case it generally just has a reflec¬ tion coefficient which differs from the rest of the peri- pheral edge of the disc. Fig. 3 shows the principle of the optical detection of the rotation of the disc 13. A light source 18 in the form of a light emitting diode or a lamp emits light through the glass panel 12 of the electricity meter, and the light im¬ pinges on the peripheral edge of the disc 13, where part of it is reflected. A light sensitive element 19 in the form of a photodiode or phototransistor is arranged in the vicinity of the light source 18 and captures reflected light from the peripheral edge of the disc 13. The opti- cally detecting elements 18, 19 are mounted in a sensor casing 15. The detecting elements 18, 19 are incorporated in a known manner in electronic circuits, which are capable of applying an electric signal in response to the intensity of the light received by the photosensor 19. When the disc 13 rotates owing to consumption of electric power, the mark 14 passes the detecting elements 18, 19 at intervals, and because the reflection coefficient of the mark differs from the rest of the peripheral edge of the disc reflecting light from the light source 18 to the photosensor 19, the intensity of the light received by the photosensor 19 varies at the passage of the mark 14. The electric circuit connected to the photosensor 19 will hereby e.g. apply an electric signal in the form of a pulse whose duration corresponds to the time it takes for "the mark 14 to pass. A central unit 10 is connected to the detecting elements 18, 19 of the sensor via an electric cable 17. The elec¬ tric pulses from the detecting elements 18, 19 of the sen- sor are accumulated in the central unit 10, and calcula¬ tions are made on the basis of this in a known manner. The central unit 10 has a keyboard by means of which data can be entered, such as number of revolutions of the disc 13 per kWh, price per kWh, etc. To prevent extraneous light from interfering with the function of the sensor, the sensor is in a known manner provided with a geometrical masking of the detecting ele¬ ments 18, 19 so that their spatial sensitivity range is restricted to a narrow angular interval positioned around a plane, and it is therefore important that the sensor is mounted on the electricity meter in such a manner that the rotating disc is positioned within this angular interval which defines the spatial sensitivity range and preferably in said plane. Further, to exclude possible interference from daylight and from electric light, the light source 18 is an infrared light emitting diode, and the photosensor is an infrared sensitive photodiode or phototransistor, and a filter allowing infrared light to pass and consider¬ ably subduing visible light is moreover fitted in front of the detecting elements 18, 19. In the preferred embodiment of the invention, which is shown in figs. 1, 2, 4, 5, 6 and 7, the detecting elements of the sensor are incorporated in a sensor casing 15, which consists of a rectangular plate 22 whose one side is formed with a box-shaped extension 23 which is narrower than the rectangular plate 22 and extends in the entire length thereof. The detecting elements 18, 19 of the sen¬ sor are incorporated in the box-shaped extension 23 appro- ximately halfway between its ends. Elongated, through- going slots 16, positioned in extension of each other, are provided on both sides of the elements 18, 19, each of said slots 16 having a depth corresponding to the total thickness of the rectangular plate 22 and the box-shaped extension 23. Figs. 1 and 4 show how these elongated slots 16 serve as aiming means when the sensor is to be mounted on the glass panel 12 of the electricity meter. By virtue of their length and depth the slots 16 define a plane extending substantially perpendicularly to the rectangular plate 22. The detecting elements 18, 19 of the sensor are positioned precisely in this plane, and the spatial sensitivity range of these elements is centered about the same plane by means of the mentioned masking. When the sensor is to be mounted on the glass panel 12 of the electricity meter, it is held in front of the glass panel, as shown in fig. 1, so that the rotating disc 13 of the electricity meter is visible through the slots 16, and before the sensor is ad¬ hered to the panel 12 by means of adhesive layers 20 on the rectangular plate 22, the sensor is placed in such a position that the circular disc 13 is seen through the slots 16, as shown in figs. 1 and 4. This ensures coin¬ cidence in practice between the plane of the disc 13 and the plane defined by the slots 16, so that the detecting elements 18, 19 of the sensor are mounted in the correct position with respect to the disc 13 whose rotation is to be detected. To ensure that the central plane of the spatial sensiti- vity range of the detecting elements 18, 19 of the sensor is arranged in a plane with the rotating disc 13, it is expedient that the aiming means have an extent in two di¬ mensions, whereby a plane is defined, and by such aiming means it will be possible to make this plane coincide with the plane of the disc 13. In practice, such aiming means do not define a plane in a mathematical sense, but define an aiming or visual angle which encircles and approximates a plane. It is then expedient in the preferred embodiment that the aiming means have elongated, parallel inlet and outlet openings at a mutual fixed distance. In case of a consumption indicating disc 13, which is ob¬ served from the edge, this disc itself defines a plane, and one-dimensional aiming means can then be arranged in the plane of the disc with good certainty. Figs. 8-12 show alternative embodiments of the aiming means of the invention. These alternative embodiments are shown to the left in the figures seen from the consumer, in the center of the figures seen from the side, and to the right in the figures seen from above. Fig. 8 shows an arragement of parallel pairs of mirrors 24 by which the disc 13 is aimed at in two areas spaced from each other, the paths of rays are displaced in parallel by means of the mirrors 24, and the two areas of the disc are observed through a lens as two half-images, which is seen to the left in fig. 8. If the sensor is misaligned with respect to the disc 13, the two half-images observed through the lens 25 will not be positioned in extension of each other, and it is then a simple matter to remedy this misalignment, because the two half-images are merely to be positioned in extension of each other and in the center of the composite image. The pairs of mirrors may be provided with aiming lines as mentioned below in connection with figs. 11-12. Fig. 9 shows how a thin wire 26 is fitted in each of the two slots 16. Here the slots 16 have a relatively greater width than in the preferred embodiment described above. The wires 26 are positioned in extension of each other, and when the sensor is mounted on the glass panel 12 of the electricity meter, the wires 26 are caused to visually coincide with the peripheral edge of the disc 13. For better definition of the aiming plane, two or more paral¬ lel wires 26 may be provided in each of the slots 16 in this plane. Fig. 10 shows an embodiment where the aiming means are formed by lenses 27 through which aiming is performed at the mounting of the sensor on the glass panel 12 on the electricity meter. The lenses 27 may be combined with others of the mentioned aiming means. Figs. 11 and 12 show a sensor casing 30 containing the detecting elements 18, 19 of the sensor. The sensor more- over comprises a transparent plate 28 carrying, on both sides of the casing 30, some lines 29 which run in exten- sion of each other in pairs. These lines 29 may be printed or painted on the plate 28 or may be scribed in its sur¬ face. These lines 29 are used as aiming means for the mounting of the sensor on the glass panel 12 on the elec- tricity meter. The embodiment in fig. 11 has two parallel lines on each side of the sensor casing 30, and when the sensor is to be mounted on the glass panel 12 of the elec¬ tricity meter the sensor is positioned such that the edge of the disc 13 of the electricity meter is seen between the two pairs of lines 29. The embodiment in fig. 12 just has one line 29 on each side of the sensor casing 30, and when the sensor is mounted, these lines are caused to co¬ incide with the edge of the disc 13. Where the electricity meter offers restricted space for the mounting of the sensor, the sensor may be constructed such that the aiming means do not form an integrated part of the sensor casing, but are merely temporarily connected with the sensor casing and can be removed. This simulta- neously results in a smaller sensor which is mounted on the consumption meter. In the first-mentioned, preferred embodiment the slots 16 are shown closed at both ends, but the slots may also be open at their ends facing away from each other. The embodiments shown here have aiming means on both sides of the detecting elements of the sensor. The aiming means may be restricted to being provided on just one side of these elements.

Claims: P a t e n t C l a i m s : 1. A sensor for optical detection of the moving parts (13, 14) of a consumption meter for visual indication of consumption, said movable parts (13, 14) of the consump¬ tion meter comprising a circular disc (13) adapted to rotate in response to the consumption and having a visible mark (14) on its periphery, said sensor having visual aim- ing means (16, 24, 26, 27, 29) assisting the mounting of the sensor on the consumption meter, c h a r a c t e r ¬ i z e d in that the aiming means (16) define a visual angle around an aiming plane. 2. A sensor according to claim 1, c h a r a c t e r ¬ i z e d in that the aiming means (16) have an inlet ope¬ ning and an outlet opening, which are slot-shaped and mu¬ tually parallel, and which are spaced from each other in the aiming plane and transversely to their longitudinal direction. 3. A sensor according to claim 2, c h a r a c t e r ¬ i z e d in that the aiming means are designed as elon¬ gated through apertures (16) in the casing of the sensor and with a considerable extent in the aiming plane. 4. A sensor according to claim 3, c h a r a c t e r ¬ i z e d in that at least one wire (26) positioned in the aiming plane is provided in each of the through apertures (16). 5. A sensor according to claims 1-4, c h a r a c t e r ¬ i z e d in that the aiming means comprise an arrangement of substantially parallel pairs of mirrors (24). 6. A sensor according to claims 1-5, c h a r a c t e r ¬ i z e d in that the aiming means comprise optical lenses (25, 27).

Inventors: CHRISTENSEN FINN, KENNER SOEREN, NEWLIN TIM, CHRISTENSEN, FINN, KENNER, SOEREN, NEWLIN, TIM
Applicants: CHRISTENSEN FINN, KENNER SOEREN, NEWLIN TIM, CHRISTENSEN, FINN, KENNER, SOEREN, NEWLIN, TIM
Application year: 1992
Main classification: G06M3
IPC codes: G01D5, G01R11, G06M1, G06M3