Analog-to-digital conversion device for sensor data in an aircraft tank

Abstract

One aspect of the invention relates to a device (20) for converting analog data from a sensor (C1,…,C3) to digital. The device (20) is intended to be connected to said sensor (C1,…,C3) located in a vehicle fluid tank (10). The device comprises: a connection module (21) to a single communication bus (40) adapted to transmit a measurement signal from the device (20) to remote measurement electronics (30) via an electrical harness passing through a wall of the tank (10); a parasitic power supply module (22) generated from the signal carried by the communication bus (40); and an acquisition and conversion module (23) configured to: acquire the analog data from the sensor (C1,…,C3), convert the acquired analog data into digital data, and transmit it via the communication bus (40) in the measurement signal. Figure to be published with the abbreviation: Figure 2

Description

Title of the invention: Analog-to-digital conversion device for sensor data in an aircraft tank. TECHNICAL FIELD OF THE INVENTION

[0001] The technical field of the invention is that of aeronautics.

[0002] The present invention relates to an analog-to-digital conversion device for sensor data in a fluid tank of a vehicle and in particular, without limitation, for fuel gauging data in an aircraft tank. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] Monitoring the fuel content in an aircraft's tank is of great importance during flight. It is therefore necessary to be able to track the quantity and density of the fuel in the tank in real time during flight with a high degree of accuracy.

[0004] For this purpose, it is known to install suitable sensors, such as gauges, densimeters and / or thermometers, in fuel tanks. Such sensors are connected to measuring electronics, located outside the tank, via a harness extending through a wall of the tank.

[0005] However, such a fuel tank constitutes a particularly difficult environment, forming in particular an explosive atmosphere due to fuel vapors, which leads to significant constraints in the choice of the type of sensors as well as their functionalities and their control.

[0006] In particular, the electronic components used must not, on the one hand, heat up or generate hot spots, especially above 200°C, and, on the other hand, store energy, especially that could generate a spark of more than 200 pj.

[0007] Usually, these sensors are of the analog and passive type, excited at low powers, so as not to risk having a component that could overheat or, in case of fault, generate a spark.

[0008] However, they require the use of a harness very well protected by highly sophisticated shielding and a complex routing to avoid measuring capacitances that could interfere with the main data acquisition. This has historically been the Achilles' heel of this type of gauging. It also requires a fairly large number of wires with point-to-point excitation of the sensors, as well as a common shielded link for measurement from the computer.

[0009] Furthermore, it is desirable to limit the measurement uncertainty of the sensors related to manufacturing variations and thus improve the reliability of the measurement. Indeed, the Manufacturing tolerances of the sensors mean that fuel volume and density measurements may exhibit dispersion from one sensor to another.

[0010] However, such improvements are made complex by the purely analog nature of the sensors.

[0011] It is also important not to significantly increase the mass of the aircraft by such improvements, nor to implement changes requiring substantial modifications to the tank, which would prove very costly.

[0012] Digital gauging has the advantage of directly conditioning the sensor values ​​in situ, which makes it possible to eliminate parasitic capacitances or other disturbances to obtain increased accuracy.

[0013] In an optical embodiment of digital gauging, a point-to-point link from each sensor to the computer is required. The fiber optic harness is fragile, expensive, and difficult to repair. The cost of the optical components makes it a system unsuitable for all projects.

[0014] In another embodiment of digital gauging in which the transmission is electrical, the harness is a daisy chain with a 2- or 4-wire data bus that allows the collection of digitized values, as well as 2 wires for power supply. Therefore, at least 4 wires are required, and a converter adds a limitation to the size of gauges that can be measured.

[0015] There is therefore a need to propose a digital gauging method that does not present the disadvantages of the state of the art. Summary of the invention

[0016] The invention offers a solution to the problems mentioned above, by allowing an inexpensive digital conversion that does not require a specific power supply wire.

[0017] One aspect of the invention relates to a device for converting analog data from a sensor to digital, the device being intended to be placed in a vehicle fluid reservoir and to be connected to a sensor located in the vehicle fluid reservoir, the device comprising: • a connection module to a single communication bus, the communication bus being adapted to transmit a measurement signal from the device to remote measurement electronics via an electrical harness passing through a wall of the tank, • a power supply module, the power supplied being parasitic power generated from the signal carried by the communication bus, • an acquisition and conversion module powered by the power supply module and configured to: • acquire the analog data from the sensor and • convert the acquired analog data into digital data and transmit it via the communication bus in the measurement signal.

[0018] Thanks to the invention, power supply wires are not necessary, because the device is powered by a parasitic power supply created from the signal carried by the communication bus.

[0019] Furthermore, the device is configured to connect to an existing sensor in a tank, and replacing the sensor does not require replacing the conversion device and conversely, replacing the conversion device does not require replacing the sensor.

[0020] By transforming the analog measurement into a digital measurement in the aircraft tank, the invention improves the reliability of transmission to the remote measurement electronics.

[0021] In addition to the characteristics just mentioned in the preceding paragraph, the device according to one aspect of the invention may have one or more complementary characteristics from among the following, considered individually or according to all technically possible combinations.

[0022] In one embodiment, the connection module is adapted to implement the “OneWire” protocol, the communication bus being of the “OneWire” type, the connection module being further adapted to convert a signal carrying the digital data from the acquisition and conversion module into the measurement signal according to the “OneWire” protocol to be transmitted via the communication bus when the communication bus is connected to the connection module.

[0023] In one embodiment, the measurement signal has a high level at 15 Volts.

[0024] In one embodiment, the power supply module includes at least one diode and a capacitor.

[0025] In one embodiment, the acquisition and conversion module is a microcontroller.

[0026] In one embodiment, the sensor is a capacitive sensor and the acquisition and conversion module is a capacitance-to-digital converter.

[0027] In one embodiment, the sensor is a densimeter and / or a thermometer.

[0028] Another aspect of the invention relates to an assembly comprising a reservoir and a remote measurement electronics including at least: • A sensor located in the tank, • a device according to the invention connected to the sensor, • an electrical harness, extending between the device and the remote measuring electronics, notably through a wall of the tank.

[0029] Another aspect of the invention relates to an aircraft comprising the assembly according to the invention, the tank being a fuel tank.

[0030] The invention and its various applications will be better understood by reading the following description and examining the accompanying figures. BRIEF DESCRIPTION OF THE FIGURES

[0031] The figures are presented for illustrative purposes only and are in no way limiting of the invention. • Figure [1] shows a schematic representation of a system comprising a plurality of devices according to the invention, • Figure [Fig. 2] shows a first schematic representation of a device according to the invention, • Figure 3 shows a schematic representation of a device according to a first embodiment of the invention, • Figure 4 shows a second schematic representation of a device according to a second embodiment of the invention compatible with the first embodiment. • Fig. 5 shows a third schematic representation of a device according to a third embodiment of the invention compatible with the first embodiment. DETAILED DESCRIPTION

[0032] Unless otherwise specified, the same element appearing on different figures has a unique reference.

[0033] Figure 1 shows a schematic representation of a system comprising a plurality of devices according to the invention. The system 1 shown in Figure 1 comprises a reservoir 10, a plurality of sensors C1 to C3, a plurality of devices 20 according to the invention, remote measuring electronics 30 and an electrical harness 40, connecting the remote measuring electronics 30 to each device 20.

[0034] The tank 10 comprises walls defining a substantially closed internal space containing a fuel, in particular in single-phase or two-phase form. The number of phases and the density of the fuel are likely to vary depending on the altitude, temperature and / or the filling level.

[0035] Due to the flammable nature of the fuel and the presence of fuel vapor in the internal space, the internal space constitutes a hazardous environment governed by the standards associated with explosive atmospheres.

[0036] The measuring electronics 30 are described as "remote" because they are not located inside the tank. The remote measuring electronics 30 are positioned outside the tank 10 and away from the fuel. Indeed, the measuring electronics 30 are not designed to operate in an explosive atmosphere, unlike the device 20.

[0037] The invention relates to an analog-to-digital conversion device 20 for measurements captured in a vehicle tank 10. Preferably, the vehicle is an aircraft. Even more preferably, the tank 10 is a fuel tank, for example, a kerosene tank. The measurements are captured by at least one sensor, preferably a plurality of sensors C1 to C3. These sensors are, for example, one or more of the following: • A capacitive sensor Cl for measuring the fuel level in tank 10, • a C2 densimeter allowing measurement of the fuel density in tank 10, • a C3 thermometer allowing the temperature of the fuel in tank 10 to be measured.

[0038] The capacitive sensor Cl is likely to be at least partially disposed in the fuel of the tank 10. The capacitive sensor Cl may comprise a first electrode and a second electrode, respectively cylindrical, concentric, and arranged vertically. In particular, the first electrode may constitute an external electrode and the second electrode may constitute an internal electrode. The first and second electrodes define an annular space between them in which the fuel rises during refueling and falls during consumption. The fuel level in the annular space thus modifies the capacitance value of the sensor Cl. In particular, the capacitance of the sensor Cl varies linearly with the fuel level in the internal space.

[0039] In particular, an electrical signal sent by the remote measuring electronics 30 to the sensor Cl via the electrical harness 40 makes it possible to determine a capacitance value of the sensor Cl for a given fuel level. Such a capacitance value can then be used by the remote measuring electronics 30 to determine the fuel level and the quantity of fuel in the tank 10.

[0040] According to another embodiment, the sensor is a densimeter C2, advantageously arranged fully immersed in the fuel and suitable for measuring a density of the fuel in the tank 10.

[0041] According to another embodiment, the sensor is a thermometer C3, advantageously arranged fully immersed in the fuel and suitable for measuring a temperature of the fuel in the tank 10.

[0042] Finally, according to a preferred embodiment, the reservoir 10 comprises at least two sensors from among the sensors Cl to C3, preferably all three sensors Cl to C3.

[0043] The sensors provide, at their terminals, i.e., at their electrodes, an analog measurement of a physical quantity. The device 20 according to the invention is adapted to connect to the terminals of a sensor, preferably reversibly, i.e., with a removable connection means. For example, as shown in [Fig. 4], the device 20 comprises two connection means, 25a and 25b respectively, each connection means being adapted to connect to one of the two electrodes of the sensor. The removable connection means 25a and 25b are, for example, as shown in [Fig. 4], screws.

[0044] The removable connection means are connected to a housing 27 comprising on-board analog / digital conversion and communication electronics via linking means 26a and 26b, for example sheathed electrical cables.

[0045] In the embodiment of [Fig. 4], the housing 27 includes a connector 28. The connector 28 allows the harness 40, and therefore the remote measurement electronics 30, to be connected to the housing 27 and thus to the analog-to-digital conversion and communication electronics that the housing 27 incorporates. Such a connector 28 makes it easier to maintain or replace the device 20. This advantage is further enhanced in combination with the screws 25a and 25b, which allow the device 20 to be removably attached to the sensor whose measurement it converts to digital.

[0046] In the embodiment of [Fig.5], the housing 27 does not include a connector 28. The harness 40 formed by two cables is then directly connected to the on-board electronics by the housing 27.

[0047] The housing 27 of the device 20 is shown in more detail in [Fig.2], which shows a schematic representation of the device 20 connected to a sensor C. The sensor C is preferably one of the sensors Cl to C3.

[0048] The device 20 includes a connection module 21, a parasitic power supply module 22 and an acquisition and conversion module 23. These three modules 21 to 23 are electronic modules.

[0049] The connection module 21 is configured to send and receive data between the device 20 and the remote measuring electronics 30, via a communication bus. For this purpose, the connection module 21 is configured to receive the two cables 401 and 402 of the harness 40, forming a communication bus between the device 20 and the remote measuring electronics 30. The communication bus is adapted to carry a signal, preferably a measurement signal from the device 20 to the remote measuring electronics 30. In a preferred embodiment, the harness 40 is of the "OneWire" type, i.e., the communication bus it forms follows the "OneWire" protocol.In this embodiment, the connection module 21 is therefore adapted to implement the "OneWire" protocol, i.e. to transform the data to be transmitted from the device 20 to the remote measurement electronics 30 via the communication bus. formed by the harness 40, in data according to the "OneWire" protocol. Such an embodiment is shown in [Fig. 3]. In the embodiment of [Fig. 3], the connection module 21 includes a OneWire communication module 211. The communication module 211 transforms the digital measurement signal from the acquisition and conversion module 23 into a OneWire digital measurement signal, and is, for example, a Maxim Integrated® DS28E18 communication bridge. In such a case, a protection diode 212 is present.

[0050] The power supply module 22 is adapted to provide power to the device 20, and in particular to provide power to the acquisition and conversion module 23. A particular feature of the invention is that the power supplied is a parasitic power supply generated from the signal carried by the communication bus. In the embodiment of [Fig. 3], the parasitic power supply module 22 is, for example, connected to the first cable 401 of the harness 40 forming the communication bus. The parasitic power supply module of [Fig. 3] then comprises a diode 221 and a capacitor 222 connected to ground. This arrangement makes it possible to return to the acquisition and conversion module 23 a portion of the communication bus voltage. Preferably, the communication bus follows an adaptation of the "OneWire" protocol.Indeed, the "OneWire" protocol is defined as having a high voltage of 5 volts, and the preferred adapted "OneWire" protocol of the present invention has its high voltage increased to 15 volts. With a capacitor 222 having a capacitance of 170 nF, this allows for more energy storage than with the standard 5-volt "OneWire" protocol. However, this stored energy must then be transmitted to the acquisition and conversion module 23, which most often operates at 5 volts. This is why the embodiment of [Fig. 3] includes an intermediate module 24. The intermediate module 24 includes a sub-module 243 for converting the 15-volt voltage to a 5-volt voltage.

[0051] The acquisition and conversion module 23 is powered by the power supply module 22. The acquisition and conversion module 23 is configured to: • acquire analog data from sensor C and • convert the acquired analog data into digital data and transmit it via the communication bus in the measurement signal.

[0052] For this purpose, the acquisition and conversion module 23 consists of a sub-module 231 connected to the two electrodes of the sensor C via connecting means 26a and 26b. The sub-module 231 is, for example, a "CDC," short for "Capacitance-to-Digital-Converter," that is, an electronic module dedicated to capacitance-to-digital conversion, for example, an AS8579 capacitive sensor from ams-OSRAM®. Alternatively, the sub-module 231 is a microcontroller, specifically programmed to perform the capacitance-to-digital conversion, or any other data. analog to digital. Alternatively, submodule 231 is any type of electronic module that enables the acquisition and conversion of analog data to digital from an existing analog sensor.

[0053] When the submodule 231 is a CDC, as shown in [Fig.3], the CDC 231 is powered via a vdd port, is connected to a clock 242 via a clk port, and includes an output port for spi digital data, in SPI format.

[0054] The data thus acquired is converted into digital format by module 23, and transmitted on the “OneWire” communication bus after being transformed into OneWire format by connection module 21. When module 23 is implemented by a microcontroller, the controller can provide, as output, digital data directly in OneWire format, module 23 thus also forming the connection module 21.

Claims

Demands

1. Device (20) for digitally converting analog data from a sensor (Cl,...,C3), the device (20) being intended to be placed in a vehicle fluid tank (10) and to be connected to said sensor (Cl,...,C3) located in the vehicle fluid tank (10), the device (20) comprising: - a connection module (21) to a single communication bus (40), the communication bus (40) being adapted to transmit a measurement signal from the device (20) to remote measurement electronics (30) via an electrical harness passing through a wall of the tank (10), - a power supply module (22), the power supply being a parasitic power supply generated from the signal carried by the communication bus (40), - an acquisition and conversion module (23) powered by the power supply module (22) and configured to: - acquire the analog data from the sensor (Cl,...,C3),C3) and - convert the acquired analog data into digital data and transmit it via the communication bus (40) in the measurement signal.

2. Device (20) according to claim 1 wherein the connection module (21) is adapted to implement the “OneWire” protocol, the communication bus (40) being of the “OneWire” type, the connection module (21) further being adapted to convert a signal carrying the digital data from the acquisition and conversion module (23) into the measurement signal according to the “OneWire” protocol to be transmitted via the communication bus (40) when the communication bus (40) is connected to the connection module (21).

3. Device (20) according to claim 2 in which the measurement signal has a high level at 15 Volts.

4. Device (20) according to any one of the preceding claims wherein the power supply module (22) comprises at least one diode and one capacitor.

5. Device (20) according to any one of the preceding claims wherein the acquisition and conversion module (23) is a microcontroller.

6. Device (20) according to any one of the preceding claims wherein the sensor (Cl,...,C3) is a capacitive sensor and the acquisition and conversion module (23) is a capacitive-to-digital converter.

7. Device according to any one of claims 1 to 5 wherein the sensor (Cl,...,C3) is a densimeter and / or a thermometer.

8. Assembly comprising a tank (10) and remote measuring electronics (30), the assembly comprising at least: - a sensor (C1,...,C3) located in the tank (10), - a device (20) according to any one of the preceding claims connected to the sensor (C1,...,C3), - an electrical harness (40), extending between the device (20) and the remote measuring electronics (30), in particular through a wall of the tank (10).

9. Aircraft comprising the assembly according to claim 8, the tank (10) being a fuel tank.

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