FR3028311A1 - SYSTEM AND METHOD FOR MEASURING THE VOLUME OF A LIQUID INCLINED IN A RESERVOIR - Google Patents

Abstract

Reservoir device (1300, 1400, 1500) for measuring the volume of at least one first liquid comprising a reservoir (RE) intended to contain said at least one first liquid (LI), said reservoir device comprising at least one cable (C1 , C2, C3, C4) disposed on the inner wall of the tank (RE) and having at least one end (D) accessible outside the tank, said at least one cable being adapted to receive an electric signal injected at said end , said signal being reflected at the interface point between said first liquid and the air, said at least one cable being arranged so that, in at least one configuration of inclination of the liquid in the reservoir, the formed plane by the interface between said first liquid and the air in the reservoir has at least three points of intersection with said at least one cable, locating the reflections of said signal in said at least one cable at said points of interest ction for determining a measurement of the volume of said first liquid in the reservoir, said reservoir device being characterized in that it is of substantially cylindrical shape and said at least one cable is disposed on the inner wall of the reservoir along all the edges of the tank and on at least a portion of the inner side wall of the tank.

Description

The invention relates to the field of systems for measuring the volume of a liquid in a tank and more particularly the measurement of the volume when the liquid is tilted in this tank. tank. The invention also relates to the field of reflectometry, a physical principle which consists in injecting a test signal into an electrical cable and then measuring its reflections on the impedance discontinuities of the cable in order to locate cable faults or changes in the cable. the nature of the medium in which the cable is immersed. The invention applies to all areas that require accurate measurement of the volume of a liquid in a tank even when the liquid is inclined. For example, the invention applies in particular to the measurement of the volume of liquid in a fuel tank for a vehicle such as a boat, a car, an aircraft or a rocket. Other possible applications include measuring the volume of a liquid in a centrifuge or measuring, in the presence of waves, the volume of the cargo of an LNG tanker or tanker. Tracking down the volume continuously and independently of the swell can help to detect anomalies preventively. The invention applies not only to inclined tanks but also to tanks subjected to constant or variable accelerations. The technical problem of the invention consists in being able to measure the volume of a liquid in a tank even when the tank, or the liquid contained in the tank, is inclined. The methods for determining the volume or level of a liquid in a reservoir are plural. The following known solutions can be cited without being exhaustive.

A first known method is the capacitive sensor method which consists in introducing a metal cylinder immersed in the center of the tank. This cylinder forms the first armature of a capacitor. This cylinder is usually covered with a thin layer of insulation. The tank, also metallic, is the second armature of the capacitor. The capacitor (cylinder + reservoir) then has a capacitance C which depends on the level of liquid in the reservoir. This method provides a reliable measurement of the level of a liquid but only works in the presence of a metal tank.

A more advanced version of capacitive sensors enables continuous measurement of liquid and bulk solids levels without direct contact. The maximum measurable height for a standard sensor is 10 cm and can be extended by serial concatenation of several elements. Methods based on ultrasound level measurement are also known. This type of method uses the propagation of an acoustic wave in the liquid, sonar principle for the detection and location of underwater objects. Another known method relates to the guided radar measurement method. A low energy electromagnetic pulse is generated in the sensor electronics, coupled into the probe. When this pulse reaches the liquid on the surface to be measured, part of the pulse is reflected back and runs along the probe to return to the electronics which then calculates the fill level from the time elapsed between sending of the impulse and its reception. The principle of using time domain reflectometry techniques to evaluate the level of a liquid in a tank is also known. For example, the documents "Microwave TDR for real-time control of intravenous drip infusions, Andrea Cataldo et al, IEEE Transactions on instrumentation and measurement, vol 61, No. 7, July 2012" and 30 "Experimental characterization and performance Evaluation of flexible twowire probes for TDR monitoring of liquid level, Andrea Cataldo et al., IEEE Transactions on Instrumentation and Measurement, March 2014 "which describe the use of a probe in the form of an electrical cable immersed in the liquid and wherein a reflectometry signal is injected and echoed to detect the transition from air to water at the cable. The methods envisaged in these documents, however, do not make it possible to measure the volume of a tank of complex shape when the reservoir or the liquid is inclined. The invention provides a system and method for measuring the volume of a liquid that functions even when the liquid is inclined in the tank, which is not possible with the methods of the prior art. The invention makes it possible to adapt to different tank shapes and also to different levels of accuracy of the electronics and sensors used by the reflectometry system. The invention is based on clever positioning of sensors by reflectometry inside the tank, on the operation of one or more measured reflectograms and on geometric calculations. The invention also makes it possible to measure the volumes of several immiscible liquids contained in the same reservoir. The invention thus relates to a reservoir device for measuring the volume of at least a first liquid comprising a reservoir intended to contain said at least one first liquid, said reservoir device being characterized in that it comprises at least one cable disposed on the inner wall of the tank and having at least one end accessible to the outside of the tank, said at least one cable being adapted to receive an electric signal injected at said end, said signal undergoing reflection at the interface point between said first liquid and air, said at least one cable being arranged so that, in at least one configuration of inclination of the liquid in the reservoir, the plane formed by the interface between said first liquid and the in the reservoir has at least three points of intersection with said at least one cable, locating reflections of said signal in said at least one cable at said intersection points for determining a measure of the volume of said first liquid in the tank. According to a particular aspect of the invention, said at least one cable is disposed on the inner wall of the tank along at least one edge of the tank. According to a particular aspect of the invention, said tank is of substantially parallelepipedal shape and said at least one cable is disposed on the inner wall of the tank along all the edges of the tank. According to a particular aspect of the invention, said reservoir device comprises a single cable disposed on the inner wall of the tank so as to cover all the edges of the tank. According to a particular aspect of the invention, said reservoir device comprises two cables arranged on the inner wall of the reservoir, each of the two cables being arranged along half of the edges of the reservoir. According to a particular aspect of the invention, said reservoir device comprises four cables arranged on the inner wall of the tank, each of the four cables being arranged along three edges of the same face of the tank. According to a particular aspect of the invention, said tank is of substantially cylindrical shape and said at least one cable is disposed on the inner wall of the tank along all the edges of the tank and on at least a part of the inner side wall. of the tank. According to a particular aspect of the invention, said reservoir device 25 comprises four cables, - each of said cables comprising a first and a second section disposed along a generatrix of the reservoir, - a first cable further comprising a third section, positioned between the first and second sections, and disposed along the perimeter of a first base of the reservoir, a second cable further comprising a third section, positioned between the first and second sections, and disposed along the perimeter of a second base of the reservoir, a third cable further comprising a third section, positioned between the first and second sections, and disposed along the circumference of a section of the reservoir by a plane perpendicular to its axis and located at a distance predetermined a first base of the tank, a fourth cable further comprising a third section, positio between the first and the second section, and disposed along the circumference of a section of the reservoir by a plane perpendicular to its axis and located at a predetermined distance from a second base of the reservoir. According to a particular aspect of the invention, said reservoir device comprises a single cable comprising a first section disposed along the perimeter of a first base of the reservoir, a second section disposed along the inner side wall of the reservoir according to an arrangement of spiral and a third section disposed along the perimeter of a second base of the reservoir.

According to a particular aspect of the invention, said reservoir device comprises a plurality of cables, each of said cables comprising a first section disposed along a portion of the perimeter of a first base of the reservoir, a second section disposed along the internal side wall of the tank and a third section disposed along a portion of the perimeter of a second base of the tank. According to a particular aspect of the invention, said at least one cable is spirally shaped so as to artificially increase its length. According to a particular aspect of the invention, said at least one cable is an insulated and homogeneous electrical cable.

According to a particular aspect of the invention, said insulated and homogeneous electrical cable is formed by two parallel or twisted conductors surrounded by an insulator or by a single conductor arranged along a ground plane. The subject of the invention is also a system for measuring the volume of at least one first liquid comprising a reservoir device according to the invention in which said at least one first liquid is contained, means for injecting at least one signal at least one end of at least one cable of said reservoir device, means for measuring at least one signal reflected in said at least one cable, means for analyzing said at least one signal reflected to identify at least one signal reflection at at least one point of said at least one cable corresponding to an interface between said first liquid and the air so as to locate at least three points of intersection between said at least one cable and the plane formed by the interface between said first liquid and the air in the tank and calculating means for determining a measurement of the volume of said first liquid in the tank from said at least three points of intersection and the dimensions of the tank. According to a particular aspect of the measuring system according to the invention, said electrical signal is a time pulse. The invention also relates to a method for measuring the volume of at least a first liquid contained in a reservoir device according to the invention, said method comprising the following steps: injecting at least one electrical signal at at least one end of at least one cable of said tank, measuring at least one signal reflected in said at least one cable, analyzing said at least one reflected signal to identify at least one reflection of the signal at at least one point of said at least one cable corresponding to a interface between said first liquid and the air so as to locate at least three points of intersection between said at least one cable and the plane formed by the interface between said first liquid and the air in the reservoir, determine by calculation measuring the volume of said first liquid in the tank from the location of said at least three points of intersection and the dimensions of the tank. According to a particular aspect of the invention, said measuring method 5 comprises the following steps: Determining, from the location of said at least three points of intersection and the length of said at least one cable, the length of the sections of the cable immersed in said at least one first liquid or the length of the cable sections emerged, Determine by geometric calculation, from the length of the submerged or emerged sections of said at least one cable, tank dimensions and the propagation speed of the signal in the submerged cable or the speed of propagation of the signal in the emerged cable, a measurement of the volume of said first liquid in the tank. According to a particular aspect of the invention, said measuring method further comprises measuring the volume of at least one second liquid immiscible with the first liquid, said method further comprising the following steps: Analyzing said at least one signal reflected to identify at least one reflection of the signal at at least one point of said at least one cable corresponding to an interface between said at least one first liquid and said second liquid so as to locate at least three points of intersection between said at least one cable and the plane formed by the interface between said at least a first liquid and said second liquid in the reservoir, determining by calculation a measurement of the volume of said second liquid in the reservoir from the location of said at least three points of intersection, reservoir size and volume measurement of said first liquid in the reservoir.

Other characteristics and advantages of the present invention will appear better on reading the description which follows in relation to the attached drawings which represent: FIG. 1, a diagram of a reservoir including a reflectrometric level sensor illustrating the principle of 2a and 2b, two diagrams illustrating the known principle of time domain reflectometry, FIGS. 3a, 3b and 3c, three diagrams illustrating the application of time domain reflectometry for the measurement of the level of a liquid. FIG. 4 is a diagram illustrating the application of the time domain reflectometry for measuring the inclination of a liquid in a tank. FIGS. 5a and 5b, two variants of a first embodiment of the invention. invention applied to a parallelepipedal reservoir, FIGS. 6a and 6b, two diagrams illustrating a second embodiment of the invention applied to a parallel tank pipedique integrating four sensors by reflectometry and the principle of measuring the volume of a liquid in such a tank when the four edges of the same face are immersed, Figures 7a and 7b, two diagrams illustrating the second embodiment of the invention applied to a parallelepiped tank and the principle of measuring the volume of a liquid in such a tank when the tank is almost full with two high corners immersed, Figures 8a and 8b, two diagrams illustrating the second embodiment of the invention applied to a parallelepiped tank and the principle of measuring the volume of a liquid in such a tank when the tank is almost full with a single not immersed corner, Figures 9a and 9b, two diagrams illustrating the second embodiment of the invention. invention applied to a parallelepipedal reservoir and the principle of measuring the volume of a liquid in such a reservoir when the reservoir see is almost empty with two low not immersed corners, Figures 10a and 10b, two diagrams illustrating the second embodiment of the invention applied to a parallelepiped tank and the principle of measuring the volume of a liquid in such a tank when the reservoir is almost empty with a single immersed wedge, FIG. 11, a diagram illustrating a third embodiment of the invention applied to a parallelepipedal reservoir incorporating two sensors by reflectometry, FIG. 12, a diagram illustrating a fourth embodiment of the invention applied to a parallelepipedal reservoir incorporating a single reflectometry sensor, FIG. 13, a diagram illustrating a fifth embodiment of the invention applied to a cylindrical reservoir incorporating four sensors by reflectometry, FIG. 14, a diagram illustrating a sixth embodiment of the invention applied to a cylinder cyli FIG. 15 is a diagram illustrating a seventh embodiment of the invention applied to a cylindrical reservoir incorporating four sensors by reflectometry, FIG. 16, a diagram illustrating an alternative embodiment of the invention. 17a and 17b, a diagram illustrating a variant of application of the invention to tanks containing at least two immiscible liquids, FIG. 18, a block diagram of a reflectometry device intended for use in all embodiments, FIGS. to be connected to one or more cables of the system according to the invention, Figure 19, a flowchart illustrating the steps of implementing the method of measuring the volume of a liquid in a tank according to the invention.

FIG. 1 schematizes an example of a reservoir RE comprising a sensor by reflectometry CA to illustrate the principle underlying the invention. The reservoir RE comprises an insulated and homogeneous AC cable, for example two parallel or twisted conductors surrounded by an insulator or a single conductor along a ground plane. The AC cable is positioned along the entire length of the inner wall of the tank. The reservoir RE is filled with a liquid LI of a height HL. One end of the cable is connected to a reflectometry system (not shown) and the other end of the cable is charged by an open circuit. A certain length of cable protrudes at the inlet and the outlet of the tank in order to eliminate the blind area problem related to the measurement principle by reflectometry. The principle of detection of the air-liquid interface in the tank is based on the propagation of electrical signals in cables or inhomogeneous media. Part of the AC cable is not immersed in the LI liquid, it is the length sections L1 and L3. Part of the cable may be immersed in the liquid depending on whether the reservoir is filled or not, this is the length section L2. The signal injected into the cable is a signal usually used in time domain reflectometry, for example a narrow pulse whose temporal width is small compared to the duration of propagation of a signal between the two ends D, T of the cable. The principle of reflectometry allows to observe all the impedance discontinuities in an inhomogeneous electrical cable. The inhomogeneity is provided by the presence of liquid around the cable. The transition between the emergent part of the cable and the immersed part can be detected via this principle. It will now be recalled, for the sake of understanding the invention, a certain number of preliminary notions concerning the transmission lines 30 and the known principle of time domain reflectometry.

A cable is a transmission line composed of two conductors separated by a dielectric (insulator). An important parameter is then defined in the transmission lines which is the characteristic impedance Zc. This characteristic impedance depends on the geometry of the cable and the properties of the dielectric. For homogeneous transmission lines, this characteristic impedance is constant over the entire length of the line. This characteristic impedance is normalized according to the field of application, for example in the field of video applications, the characteristic impedance usually has a value equal to Zc = 75 ohms, in the field of microwave applications its value is taken equal to Zc = 50 ohms while in the field of communication networks, its value is taken equal to Zc = 120 ohms. FIG. 2a shows a transmission line of length L, impedance Zc = 50 ohms, excited at one end by an internal impedance time domain reflectometry system Zg and whose other end is connected to a load. at the end of the line of impedance ZL. The speed of propagation of a wave in the transmission line is noted Vg. If an incident signal is applied in the form of a voltage pulse at one end of the line, it will propagate in the transmission line at a speed V g and reflect itself, in the form of a reflected signal, at the other end of the line to retro-propagate at the same speed to the injection plane. We will then observe at the injection plane, a pulse at t = 0 and another pulse of the same sign at 25 t = -2L, with -zL = A propagation time in the transmission line Vg Vg of length L The amplitude and polarity of the reflected pulse depend on the ZL charge at the end of the line. The reflection coefficient associated with the load ZL is equal to the ratio of the voltage reflected on the incident voltage and is expressed as follows: Z - Z F = L C ZL + Z Si ZL> Zc. then 0 <I "1 If ZL <Zc, then -1 r <o 5 If ZL = Zc, then r = o If the ZL load at the end of the line is an open circuit, we observe a SRI return pulse of identical sign If the load ZL at the end of the line is a short-circuit, then there is observed a return pulse SR2 of opposite sign to the injected pulse SI If the load ZL at the end of the line is value equal to the characteristic impedance of the line Zc, then no pulse will be reflected, in this case it is said that the line is adapted This principle is illustrated in Figure 2b Characteristic impedance and propagation velocity can to express itself according to the primary parameters of a transmission line, namely the RLCG parameters, and the dielectric properties of its insulator R: Linear resistance [Ohm / m] 20 L: Linear inductance [H / m] C: Linear capacitance [F / m] G: Linear capacitance [S / m] In the case of non or very low lines losses the characteristic impedance Zc and the propagation velocity Vg are expressed as follows: Lcg, ILcVer = Zc 1 cv = = 30c is the speed of light (-300000 km / s) Sr is the permittivity relative dielectric of the insulating material of the cable. The invention is based on the propagation of the pulses in an inhomogeneous line, that is to say in a transmission line whose characteristic impedance is not constant. The diagram of Figure 1 can be modeled according to a line model with several sections of different characteristic impedances. This transmission line is composed of three sections, as shown in Figure 3a. 113 A first section T1 of the AC cable has a length L1 of characteristic impedance Zc1. This first section corresponds to the first part of the emergent cable CA. A second section T2 corresponding to the portion of the AC cable immersed in the liquid LI, has a length L2 and a characteristic impedance Zc2. A third section T3 of the AC cable has a length L3 of characteristic impedance Zc3 = Zc1 and corresponds to the second emergent portion of the AC cable. The second section T2 has a characteristic impedance different from the other two sections T1, T3. Indeed, the characteristic impedance depends on the dielectric constant of the cable insulation. The dielectric properties of the cable insulation are modified when it is in contact with another material, in this case a liquid. For example, for a twisted pair, the characteristic impedance is expressed as follows: 2 = 76 log (DI L cr) D: Distance between the two conductors r: Conductor radius 30 When the dielectric permittivity increases, then the characteristic impedance decreases and vice versa. It is this principle that is highlighted by the invention. The cable sections T1 and T3 have the same dielectric constant er, corresponding to a contact of the cable insulation with the air, while the section T2 according to whether it is immersed or not sees its dielectric constant e. 2 modified by the contact between the insulation of the AC cable and the liquid. This implies a variation of its characteristic impedance. In this example, the dielectric permittivity of the immersed section is greater than the dielectric permittivity of the non-immersed sections, er2> erl. The zone immersed in the liquid LI forms two interfaces (an input interface and an output interface) on which we we can define two reflection coefficients, namely: Zc2 - Z ZZ c2 = F2 = I Zc.2 ClZ Zci Zc2 If Zc1> Zc2 then I; <O while F2> 0 If Zcl <Zc2 then F1> 0 while r2 G 0 Figure 3b shows the reflectogram obtained for the scenario in Figure 1. If an ID pulse is injected into the input of the AC cable, then then observe two pulses 1 and 12 of opposite signs whose time difference A depends on the liquid level LI in the reservoir RE. The IF pulse represents the end of the cable. FIG. 3c represents, in schematic form, the shape of the reflectograms obtained in the case of a reservoir of the type of FIG. 1 in three different configurations of the volume of the liquid in the reservoir.

The first reflectogram 301 corresponds to the case of a reservoir full of liquid, the second reflectogram 302 corresponds to the case of a reservoir filled with liquid at a medium level and the third reflectogram 303 corresponds to the case of an empty reservoir.

Let HL be the height of the liquid in the tank. When the liquid level is low or in the absence of liquid, HL = 0, the cable section T2 of length L2 is not immersed in the liquid, its dielectric constant er is equal to that of the two other sections T1 T3. There is no impedance discontinuity on the cable length L 10 (L1 + L2-FL3). On the corresponding reflectogram 303, no reflected pulse is observed except that of the end of the IF cable. When the height HL of the liquid in the tank increases, the length L2 of the section T2 immersed in the liquid increases. The dielectric permittivity of the section T2 passes from one value er to another value 2 following the type of liquid. The corresponding reflectogram 303 then comprises two impedance discontinuities which result in two pulses 11, 12 of opposite signs whose time difference depends on the height HL. When the height of the liquid HL in the reservoir is maximum, then the difference between the two pulses 11, 12 is maximum, as shown in the schematic reflectogram 301. In all cases, the time difference between the two echoes 11,12 gives an image of the level of liquid in the tank and thus indirectly its volume. Specifically, the length L2 of the immersed cable section is equal to L2 = (t12-tm) * V9 where tri, t12 are the temporal abscissae of the two echoes on the reflectogram and Vg is the speed of propagation of the signal in the submerged cable in LI liquid. Similarly, the lengths L1 and L3 can be determined from the knowledge of the speed of propagation of the signal in the cable located in the air. The presence of the first echo indicates the presence of a liquid in the reservoir. This echo is always automatically followed by a second echo 12 of opposite sign. With the aid of a conventional signal processing algorithm, these two pulses and their time difference are detected, then the length of the section T2 of the cable is deduced and finally the level of the liquid and its volume knowing the dimensions of the tank. By this method, it is then possible to continuously measure the level of a liquid in the reservoir described in FIG. 1. FIG. 4 illustrates the problem of measuring the volume of the liquid when the container RE is inclined. Three tank tilt positions are shown in FIG. 4, a first zero tilt position 401, a second tilt position 402 of the vessel to the right and a third tilt position 403 of the vessel to the left. On the bottom of Figure 4 are also shown the schematic diagram 501,502,503 respectively associated with the tilt positions 401,402,403 of the tank. When the tank is not inclined (position 401), there is L1 = L3 and the level and volume information of the liquid is obtained by measuring the length L2 of the immersed section T2 or the measurement of the length L1 or L3 of one of the sections T1, T2 emerged. When the tank is inclined to the right (position 402), the inclination can be detected by comparing the lengths L1 and L3 obtained by the reflectometry process. If L1 is greater than L3, this means that the tank is inclined on the side of the section T3. The liquid level and liquid volume information can always be obtained by measuring the length L2 of the section T2 and the dimensions of the tank. The same principle applies for the case of inclination 403. In the three scenarios illustrated in FIG. 4, the volume of the liquid can for example be obtained using the following relation: Vol = ((L2-D ) / 2) * A, with D the length of the cable section at the bottom of the tank and the area of the tank base. The examples described in FIGS. 1 to 4 relate to the case of a liquid having a zero inclination or limited to an axis. However, in a scenario closer to a real application, the inclination of the liquid can be done along two axes. To be able to measure the volume of the liquid in such a case, it is necessary to cleverly choose the positioning of the AC cable on the inner wall of the tank. FIG. 5a shows a first variant of a first embodiment of the invention applied to a tank of parallelepiped shape. The system 501 includes the tank RE and a cable 511 disposed along certain edges of the tank as shown in Figure 5a. The schematic reflectogram 502 illustrated is obtained by a measurement of time domain reflectometry on the cable 511 in the filling configuration of the reservoir RE by a liquid Li as indicated in FIG. 5a. The reflectogram 502 comprises a first echo 11 of opposite sign to the injected signal pulse and corresponding to a first air-> liquid transition. It then comprises a second echo 12 with the same sign as the injected pulse and corresponding to a first liquid-to-air transition. The reflectogram 502 then comprises two further echoes 13, 14 corresponding to two other respective transitions of the air to the liquid and the liquid to the air according to the path followed by the cable 511 in the reservoir. The configuration of the cable 511 on the edges of the tank, in particular on the edges of two adjacent faces of the tank, makes it possible to measure the volume of the liquid when that is inclined with a non-zero angle of inclination along two axes.

Figure 5b shows a variant of the first embodiment of the invention. The illustrated system 510 comprises two cables 521, 522 arranged along the edges of two opposite faces of the tank. For the sake of simplicity, the processing electronics connected to one end of the cable or cables is not shown in FIGS. 5a and 5b nor in the figures which follow. It should be clear, however, that a reflectometry sensor is composed of a cable, disposed on the inner wall of the tank, and a processing electronics which will be described later. In the variant shown in FIG. 5b, two different reflectograms are measured by two sensors associated with the two cables 521, 522. In the tilt configuration of the liquid shown in FIG. 5b, the two reflectograms are identical, however, when the tank tilts, one of the sensors measures a greater height of liquid than the other, which implies an imbalance. between the measurement of the first and second sensors. This imbalance is reflected in a more or less significant difference in the area immersed in the two reflectograms. We now describe a second embodiment of the invention applied to a tank of parallelepiped shape and comprising four sensors by reflectometry. This second embodiment is described in FIGS. 6a to 10b for various scenarios for filling the reservoir with a liquid and for different cases of inclination of the liquid in the reservoir. An advantage provided by this second embodiment is that it makes it possible to measure the volume of the liquid contained in the reservoir whatever the level of filling and inclination of the liquid. FIGS. 6a, 7a, 8a, 9a and 10a describe a tank 520 in the form of a block in which four cables C1, C2, C3, C4 are arranged. Each cable is positioned on the inner wall of the tank along three edges of a same face as shown in the figures. To allow a measurement of the volume of the liquid in the reservoir whatever the angle of inclination of the liquid, it is necessary that each edge is covered by a section of a cable. Without departing from the scope of the invention, other arrangements of the four cables are possible provided that the following constraints are respected: all the edges of the tank must be covered by a section and only one of a cable, the cables being disjointed between they, in other words, one edge can not be covered by two sections of two separate cables. One end of each cable is accessible from outside the tank to be connected to an electronic reflectometry device (not shown). The four ends of the four cables can be dissociated to be connected independently to the reflectometry device but they can also be brought together at the same point of entry to be simultaneously connected to the same reflectometry device. In the latter case, the reflectometry measurements are performed simultaneously on the four cables.

FIG. 6a shows a particular case of filling the tank with a certain quantity of liquid LI, the liquid having a non-zero degree of inclination. FIG. 6b shows four schematic reflectograms 601, 602, 603, 604 respectively resulting from reflectometry measurements made on the four cables C1, C2, C3, C4. The arrows shown on the cables C1, C2, C3, C4 in FIG. 6a indicate the direction of propagation of the signal injected into each cable. The reflectogram 601, associated with the cable C1, comprises a pulse 611 of opposite sign to the pulse injected into the cable, which signals the air-to-liquid transition encountered by the cable C1 at the edge HG of the tank. This pulse 611 defines on the cable C1 a first section C1,1 of the cable located in the air and a second section C1,2 of the cable located in the liquid. The temporal reflectogram 601 makes it possible to deduce the lengths of the two sections C1,1 and C1,2 of the cable and then the height Hgh of the liquid on the edge HG of the tank from the knowledge of the dimensions of the tank. Precisely, the following relations can be established from the reflectogram 601: Li + AH + HG-ling = Vair * T (Ci, i) / 2 Hhg + BG = Vliquide * T (C1,2) / 2 l is the length of the cable C1 between the point of injection of the reflectometry signal and the point A, T (C11) and T (C12) are the respective durations associated with the two sections of the cable and measured on the reflectogram 601, Vair is the speed of the wave propagating in the emerged cable and Vliquide is the speed of the wave propagating in the submerged cable.

From one or the other of these two equations, it is possible to deduce the value of Hhg. The reflectograms 602, 603, 604 make it possible, in the same way, to observe a first emergent section and a second submerged section. 15 for each cable and to deduce the heights Hfe, Hcd and Hba of the liquid on the edges EF, DC and AB of the tank. Then, the volume of the liquid in the reservoir can be calculated using the following relation: Volume (LI) = BG * BC * (max (Hhg, Hfe, Hcd, Hba) + min (Hhg, Hfa, H, d, Hba)) / Max () denotes the maximum value among the four heights, Min () denotes the minimum value among the four heights. Other geometric relationships can be used to calculate the volume of the liquid, in particular, it is possible to measure the heights of each emerged edge instead of the immersed heights. FIGS. 7a and 7b illustrate a case of application of the invention for which the reservoir is almost full of liquid, only the two upper corners A and H being emerged. FIG. 7b schematizes the reflectograms 701, 702, 703, 704 obtained respectively for the cables C1, C2, C3, C4. These reflectograms make it possible to deduce that the cable C1 has a single transition from air to liquid just like the cable C2. Cable C3 is completely submerged except for the outside of the tank. The cable C4 has a first submerged section C4,1, then a second section C4,2 emerged and a third section C4,3 immersed.

The reflectograms 701, 702, 703, 704 make it possible to deduce the Heh, Hda, Hgh, Hah heights immersed from the edges EH, DA, GH and AB. The volume of the liquid can then be calculated from these heights and the dimensions of the tank using geometric calculations.

Figures 8a and 8b illustrate a case of application of the invention for which the reservoir is almost full of liquid, only the upper corner H being emerged. FIG. 8b schematizes the reflectograms 801, 802, 803, 804 obtained respectively for the cables C1, C2, C3, C4.

In the same way, the reflectograms make it possible to determine the heights Hhe, Hah and Hgh immersed of each edge HE, AH and GH then to deduce by geometrical calculation the volume of the liquid. Figures 9a and 9b illustrate yet another application of the invention for which only the bottom corners C and F of the tank are immersed. FIG. 9b schematizes the associated reflectograms 901, 902, 903, 904 obtained respectively for the cables C1, C2, C3, C4. Finally, FIGS. 10a and 10b illustrate the case where only the bottom corner C of the tank is immersed and the associated reflectograms 1001, 1002, 1003, 1004 respectively obtained for the cables C1, C2, C3, C4. The various examples given in FIGS. 6a to 10b show that it is possible to measure the volume of the liquid irrespective of the filling and inclining configuration of the reservoir.

FIG. 11 schematizes a third embodiment of the invention 1100 which is a variant of the second embodiment comprising two cables Ci, C2 instead of four. The two cables are arranged on the inner wall of the tank so as to cover each half of the edges of the tank. The reflectometry system SR for injecting the test signal into the cables and the acquisition of the reflected signals is also shown. In the example of FIG. 11, the first cable C1 is disposed along the internal edges of the reservoir along the following path ABCFGBHG and the second cable C2 is disposed along the internal edges of the reservoir along the path AHEFDACDE. The analysis of the two reflectograms obtained from reflectometry measurements made on the two cables makes it possible, as for the second embodiment, to determine the heights immersed or emerged on each edge of the tank and then to calculate the volume of the liquid whatever its inclination. Other arrangements are possible for the arrangement of the two cables as each edge is covered by a section of one of the two cables. FIG. 12 schematizes a fourth embodiment of the invention 1200 which is yet another variant of the second embodiment but this time comprising a single cable C1 placed along all the edges of the tank. The cable C1 is disposed along the inner edges of the tank along the following path ABCADCFDEFGHEGBHA. Other arrangements are possible for the cable C1 insofar as all the edges of the tank are covered. A single reflectogram is measured in the case of the system of FIG. 12 and its analysis makes it possible to determine the same measurements as for a system comprising two or four cables. Without departing from the scope of the invention, it is possible to imagine other variants of the invention using any number of cables as long as all the edges of the tank are covered by a section of a cable. An advantage to the use of several cables, especially four, is that in this case the cables used are shorter, which limits the phenomenon of attenuation of the signal which is all the more present that the cable used is long.

In all the embodiments of the invention described above applied to a parallelepipedal reservoir, it is possible to facilitate the reflectometry measurements, in particular the conversion of the temporal reflectance measurement into distance, by adding fixing rings to each right angle to keep the reflectometry cable as close as possible to the edge of the tank. Now, with the aid of FIGS. 13, 14 and 15, other variants of the invention are now described, applied this time to a cylindrical reservoir. FIG. 13 schematizes a system 1300 according to the invention comprising a tank RE of cylindrical shape in which four cables C1, C2, C3, C4 are arranged in the manner indicated in FIG. 13. Each cable is placed on the inner wall of the tank and comprises a first outer section of the tank for connection to the reflectometry system (not shown), a second section disposed along a quarter of the perimeter of the first base of the cylinder, a third section disposed along the inner side wall. of the cylinder and a fourth section disposed along a quarter of the perimeter of the second base of the cylinder. The analysis of the four reflectograms makes it possible to measure the heights of a liquid contained in the reservoir along different axes and makes it possible, by a geometrical calculation, to deduce therefrom the volume of the liquid whatever its inclination is. in the tank knowing the dimensions of the tank. Without departing from the scope of the invention, a number N, other than four, of cables can be used in the same configuration, the second and fourth sections of each cable being then placed on 1 / Nth of the circumference of the two bases of the cable. cylinder. An advantage to using a larger number of cables is a better consideration of all the configurations of inclination and filling level of the liquid in the tank. An advantage to the use of a reduced number of cables is a simplification of algorithmic processing due to the reduced number of reflectograms to be analyzed. FIG. 14 schematizes another embodiment 1400 of the invention applied to a cylindrical reservoir RE but containing a single cable C1 disposed along the perimeter of each base of the cylinder and wound in a spiral along the inner side wall of the cylinder. . The examples of Figures 13 and 14 have the disadvantage of not comprehensively taking into account all the inclination and filling level configurations of the liquid in the tank. Indeed, depending on the spacing between two cables or two sections of the same cable, some scenarios in which the reservoir comprises a low level of liquid, may not be detected correctly. To further improve the accuracy of the calculation of the volume of the liquid contained in the reservoir whatever its level, a seventh embodiment 1500 is described in FIG. 15 in which the reservoir is of cylindrical shape and comprises four cables Ci, C2, C3, C4. The first cable C1 comprises a first outer section to the tank for connection to the reflectometry system (not shown), a second section disposed on the circumference of the first base of the cylinder and a third section disposed on the inner side wall of the cylinder, along a generator and extending to the second base of the cylinder. The second cable C2 comprises a first outer section to the tank to be connected to the reflectometry system (not shown), a second section disposed on the inner side wall of the cylinder, along a generator and extending from the first base to the to the second base of the cylinder and a third section disposed on the circumference of the second base of the cylinder.

The third cable C3 comprises a first section outside the tank to be connected to the reflectometry system, a second section disposed on the inner side wall of the cylinder, along a generator and extending from the first base to the second base of the cylinder and a third section disposed on the circumference of a section of the cylinder located at a predetermined distance from the second base of the cylinder. The fourth cable C4 includes a first outer section of the tank for connection to the reflectometry system, a second section disposed circumferentially of a section of the cylinder located at a predetermined distance from the first base of the cylinder and a third section disposed on the internal side wall of the cylinder, along a generatrix and extending from the first base to the second base of the cylinder. The four cables are arranged on the inner wall of the tank. The path of the signal injected into each cable is identified in Figure 15 by arrows. Each cable is arranged to follow this path. The use of the third and fourth cables C3, C4 makes it possible to measure the volume of the liquid contained in the reservoir even when the inclination of the liquid is different from 00 or 90 ° and the level of the liquid is low. The distance D1 between the second and the third cable and the distance D2 between the first and the fourth cable can be adjusted according to the minimum volume of liquid that it is desired to be able to measure in the tank.

From the various examples described in Figures 5 to 15, the skilled person is able to generalize the application of the invention to any type of tanks of any geometric shapes. The criterion to be fulfilled for the positioning of the OTDR cable (s) is that, in all liquid filling and inclination configurations referred to, the interface plane between the liquid and the air must have at least three points. intersection with the cable or cables disposed on the inner wall of the tank. Figure 16 schematically depicts an alternative embodiment of the invention which relates to the arrangement of the cable or cables in the tank.

According to this variant, the location accuracy of the air / liquid interfaces can be improved by artificially increasing the length of the cable C by forming it into a spiral or a zigzag shape as illustrated in FIG. 16. In this way, the localization, on a As measured reflectogram, amplitude peaks associated with air-liquid interfaces may be more accurate. Figures 17a and 17b illustrate the application of the invention to the measurement of the volume of several immiscible liquids located in the tank. Each liquid has its own relative dielectric permittivity E. For example, the permittivity of water is sr = 80 while that of benzene is equal to Er = 3.1. FIG. 17a shows a reservoir RE comprising two liquids LI1, L12. For the sake of simplicity, the reservoir RE is shown with a single cable C arranged along its inner wall, but all the embodiments with one or more cables described previously can replace the system of FIG. 17a. The dielectric permittivity of the section 302 8 3 1 1 27 of non-immersed cable is denoted by En, that of the section of cable immersed in the liquid LI1 is noted er2 and that of the cable section immersed in the liquid LI2 is denoted E3. In FIG. 17b is shown schematically the reflectogram 1700 measured on the cable C in the presence of two liquids LI1, L12. This reflectogram comprises: a first pulse 11, of opposite sign to the pulse injected into the cable, which corresponds to the first transition between the air A and the first liquid LI1, A second pulse 12, of sign identical to the pulse injected into the cable, which corresponds to the first transition between the first liquid L11 and the second liquid LI2, A third pulse 13, of opposite sign to the pulse injected into the cable, which corresponds to the second transition between the second 15 liquid L12 and the first liquid LI1, a fourth pulse 14, sign identical to the pulse injected into the cable, which corresponds to the second transition between the first liquid LI1 and the air, the gap between the first and second pulse or between the third and the fourth pulse makes it possible to determine the height of the first liquid LI1. The difference between the second pulse and the third pulse makes it possible to determine the height of the second liquid LI2. Figure 18 depicts a block diagram of an exemplary reflectometry system according to the invention. A cable 104 has, at any distance 105 from any end 106 of the cable, an impedance discontinuity due to a change of medium in which the cable is disposed. Reflectometry system 101 comprises an integrated circuit type electronic component 111, such as a programmable logic circuit, for example of FPGA type, or microcontroller, adapted to perform two functions. On the one hand, the component 111 makes it possible to generate a reflectometry signal s (t) to be injected in the cable 104 under test. This digitally generated signal is then converted via a digital-to-analog converter 112 and then injected at one end 106 of the cable. The signal s (t) propagates in the cable and is reflected on the singularity generated by the discontinuity 105. The reflected signal is backpropagated to the injection point 106 and captured 103, digitally converted via an analog-to-digital converter 113, and transmitted to the component 111. The electronic component 111 is further adapted to produce, from the signal s (t) received, a time reflectogram that can be transmitted to a processing unit 114, such as computer, personal digital assistant or other to display measurement results on a human-machine interface. The processing unit 114 is configured to analyze the time reflectogram and calculate the volume of the liquid (s) contained in the reservoir. Alternatively, the processing unit 114 can be contained directly in the system 101. In FIG. 1, only one cable has been shown, but several cables can be connected to the same reflectometry system 101 or to several different systems. If several different systems are used, they are connected to each other and to the processing unit 114 to exchange the reflectograms measured on each cable. The system 101 described in FIG. 1 is a non-limiting exemplary embodiment. In particular, the two functions performed by the component 111 can be separated in two separate components or devices, for example a first device for generating and injecting the reflectometry signal into the cable 104 and a second device for acquiring and processing the reflected signal. The processing unit 114 is configured to execute, from one or more measured reflectograms, the method for determining the volume of a liquid, the steps of which are detailed in FIG. 19.

The method according to the invention comprises the following steps. According to a first step 1901, a time domain reflectometry signal is injected at an injection point, for example an end, of a cable of the system placed on the inner wall of the reservoir containing the liquid whose volume is to be measured. This step is repeated for each cable or the same signal can be injected simultaneously in all cables. In a second step 1902, the signal injected then reflected on the impedance discontinuities of the cable is backpropagated to a measurement point, which may be confused with the injection point or not. A time reflectogram is generated from the measurement of the reflected signal. Step 1902 results in the production of as many temporal reflectograms as cables contained in the reservoir. According to a third step 1903, on each produced reflectogram, the pulses associated with impedance discontinuities caused by a change of medium in which the cable insulation is located are located so as to locate at least three discontinuities corresponding to the air-liquid interface. The analysis of the reflectogram can in particular be carried out by identifying the lengths of the sections of the cable or cables which are immersed in the liquid or which are in the opposite direction emerged. The length of each cable is known precisely. According to a fourth step 1904, from the previous analysis and the dimensions of the reservoir, the volume of the liquid is calculated using a geometric calculation.

If several immiscible liquids are contained in the reservoir, the third step 1903 is also reproduced to locate the discontinuities corresponding to the interface between two liquids and the fourth step 1904 is applied to calculate the volume of each liquid. 30

Claims (9)

REVENDICATIONS1. Reservoir device (1300, 1400, 1500) for measuring the volume of at least one first liquid comprising a reservoir (RE) intended to contain said at least one first liquid (LI), said reservoir device comprising at least one cable (C11C2) , C3, C4) disposed on the inner wall of the tank (RE) and having at least one end (D) accessible outside the tank, said at least one cable being adapted to receive an electric signal injected at said end, said signal undergoing reflection at the interface point between said first liquid and air, said at least one cable being arranged so that, in at least one configuration of inclination of the liquid in the reservoir, the plane formed by the interface between said first liquid and the air in the reservoir has at least three points of intersection with said at least one cable, locating reflections of said signal in said at least one cable at said points of interest ction for determining a measurement of the volume of said first liquid in the reservoir, said reservoir device being characterized in that it is of substantially cylindrical shape and said at least one cable is disposed on the inner wall of the reservoir along all the edges of the tank and on at least a portion of the inner side wall of the tank. 2. reservoir device (1500) according to claim 1 comprising four cables, each of said cables comprising a first and a second sections disposed along a generatrix reservoir, a first cable further comprising a third section, positioned between the first and the second section, and disposed along the perimeter of a first base of the reservoir, a second cable further comprising a third section, positioned between the first and second sections, and disposed along the perimeter of a second base of the reservoir a third cable further comprising a third section, positioned between the first and second sections, and disposed along the circumference of a section of the reservoir by a plane perpendicular to its axis and located at a predetermined distance from a first base of the reservoir, a fourth cable further comprising a third section, positioned between the first and the second section, and disposed along the circumference of a section of the reservoir by a plane perpendicular to its axis and located at a predetermined distance from a second base of the reservoir. A reservoir device (1400) according to claim 1 comprising a single cable comprising a first section disposed along the perimeter of a first base of the reservoir, a second section disposed along the inner side wall of the reservoir in a spiral arrangement. and a third section disposed along the perimeter of a second base of the reservoir. The reservoir device (1300) of claim 1 comprising a plurality of cables, each of said cables including a first section disposed along a portion of the perimeter of a first base of the reservoir, a second section disposed along the wall internal side of the reservoir and a third section disposed along a portion of the perimeter of a second base of the reservoir. 5. Tank device according to one of the preceding claims wherein said at least one cable is spirally shaped so as to artificially increase its length. 6. Tank device according to one of the preceding claims wherein said at least one cable is an insulated and homogeneous electrical cable. 7. reservoir device according to claim 6 wherein said insulated and homogeneous electrical cable is formed by two parallel conductors or twisted surrounded by an insulator or a single conductor disposed along a ground plane. 8. A system for measuring the volume of at least a first liquid comprising a reservoir device (501,510,520,1100,1200,1300,1400,1500) according to one of the preceding claims wherein said at least a first liquid, a injection means (111) of at least one electrical signal at at least one end of at least one cable (104) of said reservoir device, means for measuring (111) at least one signal reflected in said at least one a cable, means for analyzing (114) said at least one signal reflected to identify at least one reflection of the signal at at least one point (105) of said at least one cable corresponding to an interface between said first liquid and the air so as to locate at least three points of intersection between said at least one cable and the plane formed by the interface between said first liquid and the air in the reservoir and calculating means (114) for determining a volume measurement said first liquid in the tank from at least three points of intersection and dimensions of the reservoir. The system for measuring the volume of at least one first liquid according to claim 8 wherein said electrical signal is a time pulse.