OPTICAL DETECTION OF THE OPENING OF A HOUSING

Description

[0001] The invention relates to the field of detecting the opening of a housing of equipment (which may be a meter, but not necessarily). BACKGROUND OF THE INVENTION

[0002] Some malicious individuals know techniques that allow them, after opening the casing of their meter, to manipulate it to reduce their consumption. This can be any type of meter: electricity, water, gas, etc.

[0003] A number of devices are known for detecting the opening of a meter case.

[0004] In the case of water and gas meters, the detection device must consume very little electrical energy, as these meters are generally powered by a battery.

[0005] A commonly used detection device includes an electromechanical contact whose state changes when the casing is opened. However, water and gas meters are often filled with gel at the end of their manufacture. When it polymerizes, this gel tends to block the electromechanical contact and thus renders the detection device inoperative.

[0006] Documents WO2013118257A1 and EP2905585B1 disclose the respective preamble of claims 1 and 14. SUBJECT OF THE INVENTION

[0007] The invention aims to effectively detect the opening of the housing of equipment, without using electromechanical contact and consuming very little electrical energy. SUMMARY OF THE INVENTION

[0008] In order to achieve this aim, equipment according to claim 1 is provided.

[0009] Detection, achieved through emission, internal reflection, and capture of the detection light signal, is efficient, simple, and inexpensive to implement. The invention works even when the housing is filled with gel. The components used consume very little electrical energy.

[0010] Further provided is a detection method according to claim 14. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Reference will be made to the attached drawings, including: [ Fig. 1 ] there figure 1 represents a simplified sectional view, along a vertical plane, of a fluid meter; [ Fig. 2 ] there figure 2 represents steps in the detection process. DETAILED DESCRIPTION OF THE INVENTION

[0012] In reference to the figure 1 , a fluid meter 1 (for example water or gas) is intended to measure the fluid consumption of a user's (subscriber's) installation. The fluid is supplied to the installation by a distribution network.

[0013] The meter 1 comprises a box 2 and an electrical card 3.

[0014] The housing 2 here comprises a first housing part 4, a second housing part 5 and a chassis 6.

[0015] The chassis 6 comprises a lower face 7 which is also the lower face of the housing 2.

[0016] The first housing part 4 comprises an upper face 8 which is also the upper face of the housing 2, a first side face 9a and a second side face 9b. The first housing part 4 is removable. It can be removed by an operator who works for example for the fluid distributor or for the distribution network manager. The first housing part 4 is opaque to visible light (just like the chassis 6).

[0017] The second housing part 5 is transparent or translucent to visible light. It is mounted inside the housing 2, i.e. between the first housing part 4 and the inside of the meter 1. It comprises an upper face 10, a first lateral face 11a and a second lateral face 11b, which are positioned parallel to, facing and close to, respectively, the upper face 8, the first lateral face 9a and the second lateral face 9b of the first housing part 4.

[0018] The upper face 8 of the first housing part 4 has an opening 14. Light from the outside can therefore penetrate into the interior of the meter 1 via this opening 14 and the second housing part 5.

[0019] The electrical card 3 of the meter 1 is positioned parallel to and close to the upper face 10 of the second housing part 5 (and therefore to the upper face 8 of the first housing part 4).

[0020] The electrical card 3 firstly comprises a processing unit 15.

[0021] The processing unit 15 comprises at least one processing component 16, which is for example a “generalist” processor, a processor specialized in signal processing (or DSP, for Digital Signal Processor ) , a microcontroller, or a programmable logic circuit such as an FPGA (for Field Programmable Gate Arrays ) or an ASIC (for Application Specific Integrated Circuit ) . The processing component 16 here is a microcontroller.

[0022] The processing unit 15 further comprises one or more memories 17, connected to or integrated in the microcontroller 16. At least one of these memories 17 forms a computer-readable recording medium, on which is recorded at least one computer program comprising instructions which cause the microcontroller 16 to execute at least some of the steps of the detection method which will be described below.

[0023] The processing unit 15 further comprises an analog-to-digital converter (ADC) 18, possibly (but not necessarily) integrated into the microcontroller 17.

[0024] The electrical board 3 also includes an LCD screen 19, which is positioned opposite the opening 14, which allows the user to see the screen 19 through the opening 14 and the second housing part 5.

[0025] The counter 1 further comprises a device 20 for detecting the opening of the housing 1.

[0026] The detection device 20 here comprises the processing unit 15, and in particular the microcontroller 16 and the CAN 18. This does not prevent the processing unit 16 from having functions other than this, and for example metrology functions (measurement of fluid consumption).

[0027] The detection device 20 further comprises a transmitter 21 and a receiver 22, mounted on the electrical card 3.

[0028] The transmitter 21 is arranged to emit light signals, and the receiver 22 is arranged to receive the light signals after they have been reflected against an internal wall 23 of the housing 1. By “internal” is meant the inside of the meter 1.

[0029] This internal wall 23 is the internal wall of the upper face 8 of the first housing part 4. The light signals emitted by the transmitter 21 therefore pass through the second housing part 5, are reflected by the internal wall 23, then captured by the receiver 22.

[0030] The transmitter 21 is here a light-emitting diode (LED) and the receiver 22 is here a phototransistor.

[0031] The LED 21 and the phototransistor 22 are here both positioned opposite and close to the upper face 10 of the second housing part 5 of the housing 2, which is therefore itself positioned between the first housing part 4 on the one hand, and the LED 21 and the phototransistor 22 on the other hand.

[0032] The portion of the upper face 10 of the second housing part 5, opposite which the LED 21 and the phototransistor 22 are positioned, is itself positioned opposite a portion of the first housing part 4 which is a “solid” portion (and not opposite the opening 14).

[0033] Here, the LED 21 and the phototransistor 22 are positioned 5 mm apart, and at a distance of 1 cm from the inner wall 23 of the first housing part 4.

[0034] First of all, the principle of the invention is explained. It aims to detect whether the housing 2 is open or closed and therefore here, more precisely, to detect whether the first part of the housing 4 has been opened (i.e. at least one of its ends has been moved away from the rest of the housing 2).

[0035] The detection is based on the measurement of the optical reflections of a light signal emitted by the LED 21 then reflected on the internal wall 23 of the housing 2, and finally captured by the phototransistor 22.

[0036] The absence or spacing of the first part of the housing 4 leads to a limitation of the optical reflections, which causes the signal level in the phototransistor 22 to drop. This drop can be detected.

[0037] The processing unit 15 is therefore arranged to: driving the LED 21 (i.e. turning it on) so that it emits a detection light signal S 1; while the LED 21 is on, acquiring a first electrical signal produced by the phototransistor 22 when the latter receives the detection light signal S 1; detecting, as a function of a first level of the first electrical signal, whether the housing 2 is open or closed; turning off the LED 21 (this step can be carried out before the previous one).

[0038] It is noted that the emission of the detection light signal S 1 here consists simply of lighting the LED 21. The reception of the detection light signal S 1 is the capture by the phototransistor 22 of the light flux emitted by the LED 21 and reflected by the internal wall 23 (and possibly by other walls of the housing 2).

[0039] The first electrical signal here is a first voltage V 1 produced by the phototransistor 22. The first level is the amplitude of the first voltage V 1 .

[0040] The first voltage V 1 is an analog voltage.

[0041] The first voltage V 1 is digitized by CAN 18 to produce a digital signal.

[0042] This configuration is not mandatory; the receiver could in particular be a “digital” sensor.

[0043] The microcontroller 16 detects based on the first voltage V 1 whether the housing 2 is open or closed.

[0044] In order to improve the detection performance, the light energy is measured while LED 21 is lit (as just seen), then the light energy is measured without LED 21 being lit.

[0045] The order used to make the two measurements is irrelevant.

[0046] The processing unit 15 therefore acquires a second electrical signal produced by the phototransistor 22 while the LED 21 is off (i.e. it does not emit light), and detects the opening or closing of the housing 2 as a function not only of the first level of the first electrical signal (amplitude of the first voltage V 1 ), but as a function of a value representative of a difference between the first level and a second level of the second electrical signal.

[0047] The second electrical signal is a second voltage V 2 produced by the phototransistor 22. The second level is the amplitude of the second voltage V 2 .

[0048] The second voltage V 2 is an analog voltage, digitized by CAN 18.

[0049] It is therefore the analysis of the difference in lighting at the level of the receiver 22, and of the electrical signals (first voltage V 1 and second voltage V 2 ) that it generates, which makes it possible to eliminate the disturbances that would be produced by: a light ray external to counter 1 and coming to “simulate” the LED 21; a light ray external to counter 1 and coming to saturate the phototransistor 22.

[0050] In the nominal case, with the case 2 closed, the difference in brightness, measured by the phototransistor 22 with the LED 21 lit and without the LED 21 lit, is high. Indeed, a very large part of the luminous flux emitted by the LED 21 is captured by the phototransistor 22.

[0051] On the other hand, if the housing 2 is open, the luminous flux is not reflected by the inner wall 23 of the first housing part 4, which has been removed. Thus, the difference between the two measurements is significantly smaller. Of course, if the housing 2 is not completely open and if the first housing part 4 is still present but partially open, the luminous flux is still partially reflected by the inner wall 23 but to a lesser extent, which also makes it possible to detect this partial opening.

[0052] The invention works very efficiently regardless of the ambient light outside the meter 1: either ambient light is present, and the difference between the two measurements is reduced due to the illumination of the phototransistor 22 by the ambient light; or there is no ambient light, and it is the absence or reduction of reflections on the first part of the housing 4, now removed, which reduces this difference between the two measurements.

[0053] We describe more precisely, with reference to the figure 2 , the detection method, which is implemented by the processing unit 15.

[0054] The process begins with a start step: step E0.

[0055] The method includes Ph detection phases, which are continuously repeated since the initial power-up of meter 1.

[0056] When a detection phase is completed, the processing unit 15 defines a random duration, and waits for a time equal to the random duration: step E1.

[0057] This random duration is “drawn at random” after each detection phase.

[0058] This ensures that it is impossible for a potential fraudster to predict the start of the Ph detection phases. This prevents an attempt at fraud involving the emission of a light signal similar to that emitted by LED 21.

[0059] Here, the random duration is bounded between a minimum duration, equal for example to 5 seconds, and a maximum duration, equal for example to 5 minutes.

[0060] The values ​​of the random duration are here distributed uniformly, but another distribution, for example Gaussian or lognormal, is possible.

[0061] Following step E1, the Ph detection phase starts.

[0062] The processing unit 15 lights the LED 21 which emits a detection light signal S l . The processing unit 15 acquires the first voltage V 1 produced by the phototransistor 22 when the latter receives the first detection light signal S l : step E2.

[0063] Then, the processing unit 15 turns off the LED 21, and acquires the second voltage V 2 produced by the phototransistor 22: step E3.

[0064] As we have seen, the order of the two steps E2 and E3 can be reversed.

[0065] The processing unit 15 detects the opening or closing of the housing 2 as a function of a value representative of a difference between the first level of the first electrical signal (V 1 ) and the second level of the second electrical signal (V 2 ).

[0066] Here, processing unit 15 checks whether: V 1 − V 2 > V seuil where V 1 is the first voltage, V 2 is the second voltage, and V threshold is a predetermined voltage threshold (for example equal to 0.4V): step E4.

[0067] If this is the case, the processing unit 15 deduces that the box 2 is indeed closed. The detection phase ends and the method returns to step E1.

[0068] If V 1 - V 2 ≤ V threshold, the processing unit 15 detects an opening of the housing 2.

[0069] The processing unit 15 confirms this result by a second measurement (i.e. repeats steps E2, E3 and E4): step E5.

[0070] The processing unit 15 checks whether or not the detection of the opening of the housing 2 is confirmed: step E6.

[0071] If the detection of the opening of the box 2 is not confirmed, the detection phase ends and the process returns to step E1.

[0072] Otherwise, the processing unit 15 records the information that the box 2 is open, produces an alarm message and transmits it to the fluid distributor and / or the network manager: step E7.

[0073] It is possible to reuse previous measurements by filtering out non-standard measurements and averaging in order to change the predetermined voltage threshold V seuil. The predetermined voltage threshold V seuil is therefore a dynamic threshold.

[0074] The predetermined voltage threshold V threshold is for example defined from the history of previous measurements.

[0075] For example, we have: V seuil = Moy _ V 1 − Moy _ V 2 / 2 , where Avg_V 1 is the average of the values ​​of V 1 between the first and third quartiles and Avg_V 2 is the average of the values ​​of V 2 between the first and third quartiles.

[0076] Advantageously, one or more optical guides 30 are added to the housing 2 to keep the light beam concentrated and allow it to be fully reflected on the housing 2.

[0077] The counter 1 here comprises a first optical guide 30a positioned between the LED 21 and the internal wall 23, and arranged to guide and concentrate the light signals towards the internal wall 23. The counter 1 also comprises a second optical guide 30b positioned between the phototransistor 22 and the internal wall 23, and arranged to guide and concentrate the light signals towards the phototransistor 22.

[0078] The first optical guide 30a has a cylindrical shape whose axis X a extends vertically relative to the card 3 from the LED 21. The axis X a is perpendicular to the electrical card 3, to the upper face 10 of the second housing part 5 and to the upper face 8 of the first housing part 4.

[0079] The second optical guide 30b has a cylindrical shape whose axis X b extends vertically relative to the card 3 from the phototransistor 22. The axis X b is perpendicular to the electrical card 3, to the upper face 10 of the second housing part 5 and to the upper face 8 of the first housing part 4.

[0080] The first optical guide 30a and the second optical guide 30b extend vertically and perpendicularly from the inner wall 31 of the upper face 10 of the second housing part 5.

[0081] Here, the first optical guide 30a and the second optical guide 30b are manufactured in one piece.

[0082] It is noted that the meter 1 also comprises a guiding device, not shown, which makes it possible to direct the light beam from the exit of the first optical guide 30a towards the entrance of the second optical guide 30b.

[0083] Counter 1 also includes a cache device 32.

[0084] The cache device 32 comprises a first portion 32a and a second portion 32b.

[0085] The first portion 32a delimits an internal space 33 in which the receiver 22 (or at least its sensitive cell) is positioned. The first portion 32a makes it possible to prevent parasitic light signals, coming from inside or outside the housing 2, from disturbing the receiver 22.

[0086] The first portion 32a has a cylindrical shape and has as its axis an axis X c , perpendicular to the electrical card 3, to the upper face 10 of the second housing part 5 and to the upper face 8 of the first housing part 4. The axis X c here passes through a point located in the middle of the segment connecting the LED 21 and the phototransistor 22.

[0087] The first portion 32a extends vertically and perpendicularly from the inner wall 31 of the upper face 10 of the second housing part 5.

[0088] The free end of the first portion 32a is very close to the card 3 (or even in contact with it).

[0089] The cache device 32 also comprises a second portion 32b.

[0090] The second portion 32b is located between the transmitter 21 and the receiver 22. It makes it possible to prevent parasitic reflections, resulting from a reflection of the light signals emitted by the transmitter 21 on the first optical guide 30a or on the second optical guide 30b, or from lateral radiation coming from the transmitter 21, from disturbing the receiver 22.

[0091] The second portion 32b is a straight partition which extends vertically and perpendicularly from the electrical card 3. The height of this partition extends along the axis X c, and is such that the top of the partition is positioned along the axis X c close to (or even above) the free end of the optical guides 30a, 30b.

[0092] The transmitter 21 and the receiver 22 may be arranged to respectively transmit and receive light signals which are non-visible signals, i.e. which are produced by emitting light having a wavelength included in the non-visible spectrum.

[0093] This prevents a potential fraudster from noticing that the detection method is implemented in the meter 1, even if the housing 1 has a face that is transparent or translucent to visible light (like the second part of the housing 5) which could be crossed by light signals emitted by the LED 21.

[0094] Furthermore, it is possible to choose a light having a wavelength different from that of the lights normally present in the environment of the meter 1, to avoid disturbing the detection device 20. The light is thus, for example, infrared light.

[0095] It is also possible to choose a light that is more difficult for a potential fraudster to reproduce, for example a blue light.

[0096] The counter 1 may also comprise a plurality of emitters 21, generating lights of different wavelengths, which are activated alternately to ensure that there is no reproduction of the source by a potential fraudster.

[0097] The inner wall 23 of the first housing part 4 may be designed to improve reflections.

[0098] The inner wall 23 may have a concave reflector shape.

[0099] The surface of the internal wall 23 is therefore adapted to create a concave reflector (during plastic injection, for example) which will concentrate the light rays from the LED 21 by reflecting them towards the phototransistor 22.

[0100] The inner wall 23 can be made of injected plastic with a mirror finish (surface condition) in order to best reflect the light signals emitted by the LED 21.

[0101] It is possible, during the manufacture of the first housing part 4, to chemically deposit a reflective material on the internal wall 23, for example by screen printing, ink spray or paint spray.

[0102] The first housing part 4 may comprise a self-adhesive and reflective label, stuck on the internal wall 23. The self-adhesive label is selected for its reflective power and its durability over time.

[0103] The inner wall 23 may have a color having a wavelength close to the light wavelength of the internal light source (for example green if the light source is green).

[0104] The internal wall 23 has for example a color having a wavelength λ1 such as: λ 1 = λ 2 ± 10 % , where λ2 is a wavelength of the light signals emitted by the emitter 21 (i.e., the light produced by the emitter 21).

[0105] We can also bring the measurements closer together in time, without and with the light source (i.e. steps E2 and E3), so as not to be affected by the ambient lighting (50 or 60Hz) of the compact fluorescent tubes.

[0106] The invention has a large number of advantages.

[0107] It works both in the presence of resin or transparent gel in the meter 1, but also without resin or gel: as we have seen, unlike devices comprising an electromechanical contact, the invention works effectively even in the presence of resin or gel.

[0108] The electrical power consumption of the detection device 20 is very low. The device 20 consumes little current because it is activated for a very short time and switched off for random and much longer periods. This limits the possible reliability drift of the optical components. The device 20 fits perfectly in battery-powered equipment (such as the meter 1).

[0109] The consumption of the device 20 (LED 21, phototransistor 22, CAN 18 and microcontroller 16) is approximately 0.5 mA average for 1 ms, or 0.5 µAsec. The duration of a Ph detection phase being at least 5 seconds, the consumption is 0.1 µAsec therefore totally negligible.

[0110] The device 20 is very simple to implement and has a low cost. The components used (for example the LED 21 and the phototransistor 22) are standard components which do not need to be fast or sensitive.

[0111] The device 20 is easily adaptable and can be installed on existing products without modification.

[0112] The device 20 is very sensitive. The device 20 is capable of detecting a very slight opening of the housing 2. It can even detect water infiltration between the housing 2 and the gel of " potting » or between the first housing part 4 and the second housing part 5 due to the effect of water on the light rays.

[0113] The device 20 is robust to electronic interference, making disruption by counterfeiters difficult, and making it possible to use it in complex electromagnetic environments.

[0114] The device 20 makes it possible to take all necessary measures, such as erasing keys, raising an alarm and / or transmitting this alarm to the monitoring network.

[0115] This solution is simple, energy-efficient, and can easily adapt to the mechanical dimensions of all products.

[0116] The device 20 makes it possible to overcome fraud attempts. It is thus capable of thwarting product openings in a lit room or in absolute darkness.

[0117] Of course, the invention is not limited to the embodiments described but encompasses any variant falling within the scope of the invention as defined by the claims.

[0118] The equipment in which the invention is implemented is not necessarily a fluid meter. It can be any type of meter and even, more generally, any type of equipment.

[0119] The emitter is not necessarily an LED, but could be any type of photoemitter, for example a laser diode.

[0120] The receiver is not necessarily a phototransistor, but could be any type of photoreceptor, for example a photodiode.

[0121] The electrical architecture shown may differ from the one described here. For example, the transmitter and receiver may be integrated into a single component, directly into a housing part, etc. Not all electrical components are necessarily mounted on the same board.

[0122] The housing may differ from the one shown here. The second housing part is optional. The housing does not necessarily have a removable housing part (such as the first housing part), and the detection device could detect an opening of the housing by breaking it.

[0123] If the housing does not include the second housing part, the transmitter and receiver may be positioned opposite and in proximity to the first housing part.

[0124] The detection is carried out here according to a value representative of a difference between the first level of the first electrical signal and the second level of the second electrical signal. This value is therefore not necessarily equal to the difference between the first level of the first electrical signal and the second level of the second electrical signal. It could be, for example, a difference between the second level and the first level, etc.

Claims

1. A piece of equipment (1) comprising a housing (2) in which the following are incorporated: - an emitter (21) arranged to emit light signals; - a receiver (22) arranged to receive the light signals after they have been reflected against an inner wall (23) of the housing; - a processing unit (15) arranged to: ∘ control the emitter (21) so that it emits a detection light signal (SI); ∘ acquire a first electrical signal (V1) produced by the receiver (22) when it receives the detection light signal; ∘ detect, on the basis of a first level of the first electrical signal, whether the housing (2) is open or closed, the processing unit (15) being characterized in that it is further arranged to: - acquire a second electrical signal (V2) produced by the receiver while the emitter is deactivated; - detect the opening or closing of the housing on the basis of a value representative of a difference between the first level of the first electrical signal (V1) and a second level of the second electrical signal (V2).

2. A piece of equipment according to claim 1, in which the housing (2) comprises a first housing part (4), which is removable, the inner wall (23) being a wall of the first housing part, and in which the emitter and the receiver are both positioned: - opposite and in the vicinity of the first housing part; or - opposite and in the vicinity of a second housing part (5) of the housing, which is transparent or translucent to light signals, and positioned between the first housing part, and the emitter and the receiver.

3. A piece of equipment according to one of the preceding claims, further comprising: - a first optical guide (30a) positioned between the emitter (21) and the inner wall (23), and arranged to guide and concentrate the light signals towards the inner wall; - a second optical guide (30b) positioned between the receiver (22) and the inner wall, and arranged to guide and concentrate the light signals towards the receiver.

4. A piece of equipment according to claim 3, in which the first optical guide (30a) and the second optical guide (30b) are manufactured as a single part.

5. A piece of equipment according to one of the preceding claims, further comprising a masking device (32) comprising a first portion (32a) delimiting an inner space in which the receiver (22) is positioned, and arranged to prevent spurious light signals originating from inside or outside the housing (2) from interfering with the receiver.

6. A piece of equipment according to claims 3 and 5, in which the masking device (32) also comprises a second portion (32b) situated between the emitter (21) and the receiver (22), and arranged to prevent spurious reflections, resulting from the reflection of the light signals emitted by the emitter (21) on the first optical guide (30a) or on the second optical guide (30b), or from lateral radiation originating from the emitter (21), from interfering with the receiver (22).

7. A piece of equipment according to one of the preceding claims, in which the inner wall (23) is made from injection-moulded plastic with a mirror finish.

8. A piece of equipment according to one of the preceding claims, in which the inner wall (23) has the shape of a concave reflector.

9. A piece of equipment according to one of the preceding claims, comprising a reflective material chemically deposited on the inner wall (23).

10. A piece of equipment according to one of the preceding claims, comprising a self-adhesive reflective label stuck to the inner wall (23).

11. A piece of equipment according to one of the preceding claims, in which the colour of the inner wall (23) has a wavelength λ1 such that: λ 1 = λ 2 ± 10 % , where λ2 is a wavelength of the light signals.

12. A piece of equipment according to one of the preceding claims, the emitter and the receiver being arranged to respectively emit and receive light signals that are non-visible signals.

13. A piece of equipment according to one of the preceding claims, the equipment being a fluid meter (1).

14. A detection method, implemented in the processing unit of a piece of equipment according to one of the preceding claims, and comprising a detection phase (Ph) comprising the steps of: - controlling the emitter (21) so that it emits a detection light signal (Sl); - acquiring a first electrical signal (V1) produced by the receiver when it receives the detection light signal; - detecting, on the basis of a first level of the first electrical signal, whether the housing (2) is open or closed. the detection phase being characterized in that it further comprises the steps of: - acquiring a second electrical signal (V2) produced by the receiver while the emitter is deactivated; - detecting the opening or closing of the housing on the basis of a value representative of a difference between the first level of the first electrical signal (V1) and a second level of the second electrical signal (V2).

15. A detection method according to claim 14, comprising the steps of: - repeating the detection phase; - when a detection phase is complete, defining a random time period, and starting a subsequent detection phase after the random time period.

16. A computer program comprising instructions that cause the processing unit of the electrical equipment according to claim 1 to perform the steps of the detection method according to claim 14.

17. A computer-readable storage medium on which the computer program according to claim 16 is stored.