Device for analog-to-digital conversion of sensor data in an aircraft tank

Abstract

One aspect of the invention relates to a device (20) for digital conversion of analog data from a sensor (C1,…,C3), the device (20) being intended to be connected to said sensor (C1,…,C3) located in a vehicle fluid tank (10), comprising: 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) by an electrical harness passing through a wall of the tank (10), a parasitic power supply module (22) generated from the signal transported by the communication bus (40), an acquisition and conversion module (23) configured to: acquire the analog data from the sensor (C1,…,C3) and 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 abstract: Figure 2

Description

Title of the invention: Device for analog-digital conversion of 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 a device for analog-to-digital conversion of sensor data in a fluid tank of a vehicle and in particular, without limitation, of fuel gauge data in an aircraft tank. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] Control of fuel contained in a tank of an aircraft is of great importance during a flight. It is therefore necessary to be able to monitor a measurement of a quantity and density of the fuel in the tank in real time during the 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 the 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 the 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, in particular above 200°C, and, on the other hand, store energy, in particular likely to 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 which could heat up or, in the event of a fault, generate a spark.

[0008] However, they require the use of a harness that is very well protected by shielding with very precise construction and a complex route to avoid measuring capacitances interfering with the main acquisition. This is historically 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 connection for measurement from the computer.

[0009] In addition, it is desirable to limit the measurement uncertainty of the sensors linked to manufacturing variations and thus improve the reliability of the measurement. Indeed, the Sensor manufacturing tolerances mean that fuel volume and density measurements may vary from sensor to sensor.

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

[0011] It is further 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 stray capacitances or other disturbances to obtain increased precision.

[0013] In an optical embodiment of digital gauging, a point-to-point connection from each sensor to the computer is necessary. The fiber optic harness is fragile, expensive, and difficult to repair. The cost of the optical components makes it a system that is not suitable for all projects.

[0014] In another embodiment of digital gauging in which the transmission is electrical, the harness is in a "daisy chain" with a data bus on 2 or 4 wires which allows the collection of digitized values ​​as well as 2 wires for the power supply. It is therefore necessary to have at least 4 wires, and a converter adds a limitation in the size of gauges for the measurement.

[0015] There is therefore a need to propose a digital gauging system which does not have the drawbacks of the state of the art. Summary of the invention

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

[0017] One aspect of the invention relates to a device for digitally converting analog data from a sensor, 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 module for connection 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 a parasitic power supply generated from the signal transported 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 transported by the communication bus.

[0019] In addition, 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 digital measurement in the aircraft tank, the invention improves the reliability of transmission to the remote measurement electronics.

[0021] In addition to the characteristics which have just been mentioned in the preceding paragraph, the device according to one aspect of the invention may have one or more complementary characteristics 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 coming 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 comprises 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 measuring electronics comprising 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, in particular 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 upon reading the following description and examining the accompanying figures. BRIEF DESCRIPTION OF THE FIGURES

[0031] The figures are presented for information purposes only and in no way limit the invention. • [Fig.l] shows a schematic representation of a system comprising a plurality of devices according to the invention, • [Fig.2] shows a first schematic representation of a device according to the invention, • [Fig.3] shows a schematic representation of a device according to a first embodiment of the invention, • [Fig.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 in different figures has a single reference.

[0033] [Fig.l] shows a schematic representation of a system comprising a plurality of devices according to the invention. The system 1 shown in [Fig.l] comprises a tank 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 may vary depending on the altitude, the temperature and / or the filling rate.

[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 standards associated with explosive atmospheres.

[0036] The measuring electronics 30 are said to be “remote” because they are not present inside the tank. The remote measuring electronics 30 are arranged outside the tank 10 and away from the fuel. Indeed, the measuring electronics 30 are not suitable for operating in an explosive atmosphere, unlike the device 20.

[0037] The invention relates to a device 20 for analog / digital conversion of measurements captured in a vehicle tank 10. Preferably, the vehicle is an aircraft. Preferably again, the tank 10 is a fuel tank, for example kerosene. 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 sensors among: • A capacitive sensor Cl for measuring the fuel level in the tank 10, • a C2 densimeter for measuring the fuel density in tank 10, • a C3 thermometer for measuring the temperature of the fuel in tank 10.

[0038] The capacitive sensor C1 is capable of being at least partially arranged in the fuel of the tank 10. The capacitive sensor C1 may comprise a first electrode and a second electrode, respectively cylindrical, concentric, arranged vertically. In particular, the first electrode may constitute an external electrode and the second electrode may constitute an internal electrode. The first electrode and the second electrode define between them an annular space in which the fuel rises during filling and descends during consumption. The fuel level in the annular space thus modifies the capacitance value of the sensor C1. The capacitance of the sensor C1 varies in particular 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 C1 via the electrical harness 40 makes it possible to determine a capacitance value of the sensor C1 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 C2 densimeter, advantageously arranged entirely immersed in the fuel and capable of measuring a density of the fuel in the tank 10.

[0041] According to another embodiment, the sensor is a C3 thermometer, advantageously arranged entirely immersed in the fuel and capable of 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 among the sensors C1 to C3, preferably the three sensors C1 to C3.

[0043] The sensors provide, at their terminals, that is to say 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 connection means 26a and 26b, for example sheathed electrical cables.

[0045] In the embodiment of [Fig.4], the housing 27 comprises a connector 28. The connector 28 makes it possible to connect the harness 40 and therefore the remote measurement electronics 30 to the housing 27 and therefore to the analog / digital conversion and communication electronics that the housing 27 incorporates. Such a connector 28 makes it possible in particular to facilitate maintenance or standard exchange of the device 20. This advantage is further improved in combination with the screws 25a and 25b, which allow removable attachment of the device 20 to the sensor whose measurement it converts into digital.

[0046] In the embodiment of [Fig.5], the box 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 box 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 C1 to C3.

[0048] The device 20 comprises 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 measurement electronics 30, via a communication bus. For this, 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 measurement electronics 30. The communication bus is adapted to transport a signal, preferably a measurement signal coming from the device 20 and destined for the remote measurement electronics 30. In a preferred embodiment, the harness 40 is of the “OneWire” type, that is to say that the communication bus that it forms follows the “OneWire” protocol.In this embodiment, the connection module 21 is therefore adapted to implement the “OneWire” protocol, that is to say to transform the data to be transmitted, from the device 20 to the remote measuring electronics 30 via the communication bus. formed by the harness 40, into data according to the “OneWire” protocol. Such an embodiment is shown in [Fig.3]. In the embodiment of [Fig.3], the connection module 21 comprises a OneWire communication module 211. The communication module 211 makes it possible to transform the digital measurement signal coming from the acquisition and conversion module 23 into a OneWire digital measurement signal, and is for example a DS28E18 communication bridge from Maxim Integrated®. In such a case, a protection diode 212 is present.

[0050] The power supply module 22 is adapted to provide a power supply to the device 20, and in particular to provide a power supply to the acquisition and conversion module 23. A particular feature of the invention is that the power supply provided is a parasitic power supply generated from the signal transported 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 assembly makes it possible to restore part of the voltage of the communication bus to the acquisition and conversion module 23. Preferably, the communication bus follows an adaptation of the “OneWire” protocol.Indeed, the “OneWire” protocol is defined as comprising a high value at 5 Volts, and the preferred adapted “OneWire” protocol of the present invention has its high value increased to 15 Volts. With a capacitor 222 having a capacitance of 170nF, this allows for more energy to be stored than with the standard “OneWire” protocol at 5 Volts. But 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] comprises an intermediate module 24. The intermediate module 24 comprises 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, the acquisition and conversion module 23 is formed 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”, from the English “Capacitance-to-Digital-Converter”, that is to say an electronic module dedicated to the capacitance to digital conversion, for example an AS8579 capacitive sensor from ams-OSRAM®. Alternatively, the sub-module 231 is a microcontroller, specifically programmed to carry out the capacitive to digital conversion, or any other data analog to digital. Alternatively, submodule 231 is any type of electronic module that allows the acquisition and conversion of analog data to digital from an existing analog sensor.

[0053] When the sub-module 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 the digital data spi, in SPI format.

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

Claims

Claims

1. Device (20) for digital conversion of 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) by an electrical harness passing through a wall of the tank (10), - a power supply module (22), the power supply provided being a parasitic power supply generated from the signal transported 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) 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 according to which the connection module (21) is adapted to implement the “OneWire” protocol, the communication bus (40) being of the “OneWire” type, the connection module (21) being further adapted to convert a signal carrying the digital data coming 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 one of the preceding claims in which the power supply module (22) comprises at least one diode and one capacitor.

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

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

7. Device according to 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 (Cl,...,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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