Sensor for an aircraft tank

Abstract

The invention relates to a sensor (24) for measuring at least one of the amount and / or density of fuel (18) in an aircraft fuel tank (10), comprising:-at least one probe (26) configured to measure at least one of the amount and / or density of fuel, intended to be arranged within an interior space (16) of the fuel tank (10); a memory (38) arranged within the interior space (16) and configured to store at least some values of a calibration parameter of the probe (26); and-a single communication bus intended to connect the probe (26) and the memory (38) to the remote measurement electronics (20) by means of a wire harness (22) passing through the wall (14) of the tank (10).

Description

Technical Field

[0001] The present invention relates to a sensor installed in an aircraft fuel tank, in particular a sensor for measuring at least the amount of fuel in the aircraft fuel tank, as well as an assembly including the sensor and a related control method. Background Art

[0002] Monitoring the fuel in an aircraft's fuel tanks during flight is extremely important. Therefore, it is necessary to be able to monitor the fuel quantity and density in the tanks in real time during flight with high accuracy.

[0003] For this purpose, it is known to install suitable sensors in the fuel tank, such as level gauges, density gauges and temperature gauges. These sensors are connected to measuring electronics located outside the tank via wiring harnesses passing through the tank wall.

[0004] However, such fuel tanks constitute a particularly harsh environment, as fuel vapors form an explosive atmosphere, which imposes significant restrictions on the choice of sensor type and its functionality and management.

[0005] In particular, the electronic components used must not overheat or generate hot spots, in particular above 200°C, and must not store energy, in particular energy that could generate sparks exceeding 200 μJ.

[0006] Typically, these sensors are analog and passive, excited at low power levels to avoid the risk of sparking if the component overheats or fails.

[0007] Nevertheless, it is desirable to limit the sensor measurement uncertainty associated with manufacturing variations, thereby improving measurement reliability. In practice, tolerances in sensor manufacturing mean that fuel volume and density measurements can vary from sensor to sensor.

[0008] However, the purely analog nature of the sensor complicates such improvements.

[0009] It was also important not to significantly increase aircraft weight through such modifications, nor to implement changes that would require major modifications to fuel tanks and wiring harnesses, which would prove very expensive.

[0010] Finally, the sensors must be as simple as possible in design to maximize their reliability, especially given the difficulty in accessing them when replacing them inside the tank. Summary of the Invention

[0011] The present invention is therefore directed to improving the accuracy of the measurement of the amount and / or density of fuel present in an aircraft tank without requiring major reconfiguration of the wiring harness or the tank.

[0012] To this end, the present invention relates to a sensor for measuring at least one of the quantity and / or density of fuel in an aircraft tank, comprising:

[0013] - at least one probe configured to measure at least one of the quantity and / or density of the fuel, intended to be arranged in the interior space of the tank;

[0014] a memory, in particular an electrically erasable programmable read-only memory, arranged in the interior of the tank and configured to store at least some values ​​of the calibration parameters of the probe; and

[0015] A single communication bus, in particular composed of at least two conductors, is intended to connect the probe and the memory to the remote measurement electronics by means of a wiring harness passing through the wall of the tank.

[0016] Such a sensor allows access to specific calibration data of the measuring probe by the measuring electronics, in particular remotely, which improves measurement accuracy and reliability without requiring modifications to the tank and wiring harness.

[0017] In particular, the communication bus is of a type known as "One-Wire".

[0018] Therefore, according to the invention, it is proposed to add a memory to a purely analog probe, the memory being configured to store at least the values ​​of the calibration parameters of the probe, these values ​​being accessible via the same conductors used by the probe, the probe not having such a memory.

[0019] The probe may be a level gauge, in particular a capacitance measuring level gauge, comprising two electrodes connected respectively to a low impedance conductor and a high impedance conductor of a communication bus, the communication bus being protected by a shielding layer.

[0020] Furthermore, the memory is connected, for example, between a high-impedance conductor and a shield of the communication bus.

[0021] Such a feature allows for simple and reliable measurement of the amount and / or density of fuel in a tank in a purely analog manner and without involving significant current or heat.

[0022] Such features also allow for higher accuracy than known prior art sensors.

[0023] The sensor may include at least one diode connected in parallel with the memory and / or at least one resistor connected in series with the memory.

[0024] Such a feature provides effective protection for the memory and sensors against overvoltage.

[0025] The memory may be mounted on a printed circuit board placed in a housing located within the interior space of the tank, in particular on the probe.

[0026] More specifically, the housing can contain a resin in which the printed circuit board and memory are embedded. Such a feature isolates the electrical components from the fuel in the tank.

[0027] The memory may be an electrically erasable programmable read-only memory. Such a feature allows data to be stored in a component requiring very little power and reducing any risk from heating.

[0028] The value of the calibration parameter may include two capacitance values ​​of the probe measured at two different fill percentages of the tank.

[0029] Furthermore, depending on the linearity of the sensor, more than two calibration parameters may be stored.

[0030] Such a feature allows the measurement results to be corrected by linear interpolation or by piecewise nonlinear response curves to correct for variations due to probe manufacturing tolerances.

[0031] Alternatively, the probe may be a densitometer consisting of two windings forming a transformer connected to an excitation circuit.

[0032] When the probe is a densitometer, the values ​​of the calibration parameters of the probe may include mechanical correction parameters related to its manufacture. Such a feature allows the density measurement to be compensated by eliminating variations related to manufacture.

[0033] Thus, according to the present invention, the probe is capable of measuring the fuel height and / or density of fuel passing through it or in which it is partially or completely immersed.

[0034] The sensor may also include a measuring probe, in particular a passive one, capable of measuring any other physical property of the fuel, such as temperature, dielectric constant, etc.

[0035] More specifically, the sensor may also include a temperature measuring probe, in particular a digital temperature measuring probe, more particularly integrated into a memory and accessible via the communication bus. Such a feature allows taking into account measurement variations due to the fuel temperature.

[0036] In particular, the communication bus may be of a two-wire type comprising two conductors and their insulation, such as a coaxial cable, a twisted pair, or the like.

[0037] The invention also relates to an assembly comprising a fuel tank and a measuring system, the measuring system comprising at least:

[0038] - a sensor as described above,

[0039] - control electronics, and

[0040] - A wiring harness, extending between the sensors and the control electronics, in particular through the wall of the fuel tank.

[0041] The invention also relates to a method for measuring at least one of the quantity and / or density of fuel in a tank, using a sensor as described above and measurement electronics connected to the sensor.

[0042] The measurement methods shall include at least:

[0043] - an acquisition step during which at least one value of a calibration parameter of the probe is acquired;

[0044] - a storing step during which the values ​​of the calibration parameters are stored in a memory;

[0045] a reading step during which the value of the calibration parameter is read from the memory by the measuring electronics each time the measuring electronics is started; and

[0046] An acquisition step for acquiring a measurement of the amount and / or density of the fuel, during which the measurement electronics acquires a measurement of the amount and / or density of the fuel by using the probe with the aid of the values ​​of the calibration parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The invention will be better understood and other features and advantages will become further apparent on reading the following detailed description, which includes examples given by way of non-limiting examples with reference to the accompanying drawings, which serve to complete the understanding of the invention and the description of its embodiments and, where appropriate, contribute to its definition, in which:

[0048] [ Figure 1 ] Figure 1 is a schematic diagram of an assembly comprising a fuel tank and a measuring system comprising a sensor according to the invention, and

[0049] [ Figure 2 ] Figure 2 yes Figure 1 Schematic diagram of the sensor. DETAILED DESCRIPTION

[0050] Figure 1 Schematically shown is a fuel tank 10, in particular for an aircraft, and a measuring system 12 capable of determining the amount and / or density of fuel 18 present in the tank 10. Advantageously, the measuring system 12 is particularly configured to measure the amount and / or density of the fuel 18 present in the tank 10.

[0051] The measurement system 12 may also be configured to measure the temperature of the fuel 18 present in the tank 10 .

[0052] The fuel tank 10 includes walls 14 defining a substantially enclosed interior space 16 containing fuel 18 , particularly in single-phase or two-phase form.

[0053] The number of phases and density of the fuel 18 may vary depending on altitude, temperature, and / or fill percentage.

[0054] Due to the flammable nature of the fuel 18 and the presence of fuel vapors in the interior space 16 , the interior space 16 constitutes a hazardous environment governed by standards relating to explosive atmospheres.

[0055] The measuring system 12 comprises measuring electronics 20, a wiring harness 22 and at least one sensor 24, which is arranged in the interior 16 of the tank 10. In particular, the sensor 24 can be at least partially immersed in the fuel 18.

[0056] The measuring electronics 20 comprises, for example, at least one processor and at least one memory, not shown in the figure. The measuring electronics 20 is, for example, integrated into an onboard computer and can be connected to other avionics equipment.

[0057] The measuring electronics 20 are arranged outside the tank 10 and away from the fuel 18. In practice, the measuring electronics 20 are not suitable for operation in explosive atmospheres.

[0058] The wiring harness 22 is an assembly comprising one or more electrical cables grouped in a protective sheath. The wiring harness 22 extends from the measurement electronics 20 through the wall 14 of the tank 10 to the sensor 24 to allow connection of electrical signals between the sensor 24 and the measurement electronics 20.

[0059] The wiring harness 22 may be quite long, for example between 10 and 50 meters.

[0060] The sensor 24 includes at least one probe 26 , which is arranged in the interior 16 of the fuel tank 10 .

[0061] According to one embodiment, the probe 26 is of the capacitance measuring type and is arranged in the interior space 16 of the tank 10 .

[0062] According to another embodiment, the probe 26 is of the transformer turns ratio measurement type and is arranged in the interior space 16 of the tank 10 .

[0063] Figure 2 yes Figure 1 Schematic diagram of sensor 24.

[0064] More specifically, according to Figure 2 In one embodiment shown in FIG. 1 , the probe 26 is a level gauge or a density gauge for measuring the density of the fuel in the fuel tank 10 .

[0065] Such a probe 26 may be arranged at least partially within the fuel 18. The probe 26 may include a first electrode 28 and a second electrode 30, each cylindrical, coaxial and vertically arranged, in particular in the case of a capacitance level gauge. Figure 2 In the example shown, the first electrode 28 may constitute the outer electrode 28 , and the second electrode 30 may constitute the inner electrode 30 .

[0066] The first electrode 28 and the second electrode 30 define an annular space 32 therebetween, which rises when filled and falls when consumed by the fuel 18. Thus, the level of the fuel 18 in the annular space 32 changes the capacitance value of the probe 26.

[0067] The capacitance of the probe 26 varies in particular linearly with the fill level of the fuel 18 in the interior space 32 .

[0068] In particular, the electrical signal sent by the measurement electronics 20 to the probe 26 allows the capacitance value of the probe 26 to be determined for a given fuel level. Such capacitance value can then be used by the measurement electronics 20 to determine the level of fuel 18 in the tank 10 and the amount of fuel 18.

[0069] According to another embodiment, the probe 26 is a densitometer, advantageously arranged so that it is completely immersed in the fuel 18 and is able to measure the density of the fuel 18 in the tank 10 .

[0070] According to another embodiment, the sensor 24 includes a probe 26 capable of determining the level of the fuel 18 in the tank 10 and a densitometer capable of measuring the density of the fuel 18 in the tank 10 .

[0071] Optionally, the sensor 24 may also include a temperature probe.

[0072] The sensor 24 further includes a printed circuit board 34, which may be disposed within the interior space 16 of the fuel tank 10. For example, the printed circuit board 34 is housed within a protective housing 36.

[0073] The printed circuit board 34 includes various electronic components used for the measurements taken by the sensor 26 , depending on the type of measurement.

[0074] Advantageously, the housing 36 is filled with a resin in which the printed circuit board 34 is embedded, so as to prevent any contact between the printed circuit board 34 and the fuel 18 .

[0075] The printed circuit board 34 comprises in particular a memory 38, more particularly an electrically erasable programmable read-only memory (EEPROM).

[0076] For example, the memory 38 has a storage capacity of 1024 bits.

[0077] This type of memory 38 is a component that is able to passively store data without the need for power, so the stored information is not lost when power is no longer supplied.

[0078] Furthermore, such a memory 38 requires very little current and low voltage to access the stored data.

[0079] Finally, such a memory 38 generates only a small amount of heat, which can be considered negligible.

[0080] According to an example embodiment, memory 38 is self-powered between ground line 40 and data line 42, in a so-called "parasitic power supply" arrangement.

[0081] The memory 38 is configured to store at least some values ​​of calibration parameters of the probe 26 , in particular values ​​of at least two calibration parameters of the probe 26 .

[0082] These values ​​are specific to the probe 26 and enable manufacturing tolerances to be taken into account.

[0083] The values ​​of the calibration parameters may include, for example, a capacitance value of the probe 26 measured when the fuel tank 10 is empty and a capacitance value of the probe 26 measured when the fuel tank 10 is filled with fuel 18 .

[0084] More generally, the value of the calibration parameter may include capacitance values ​​measured at different levels of the fuel 18 in the tank 10 , in particular two levels of the fuel 18 in the tank 10 corresponding to different known fill percentages of the tank 10 .

[0085] Alternatively, the values ​​of the calibration parameters may include, for example, an offset value of the probe 26 and a gain value of the probe 26, i.e., respective values ​​of the intercept and slope of an affine function between the measured capacitance of the probe 26 and the level of the fuel 18 in the tank 10 or the fill percentage of the tank 10 and / or the density of the fuel 18.

[0086] Furthermore, in the case where the probe 26 is a densitometer, the calibration parameter may be a voltage ratio corresponding to a density value, temperature compensation, or others.

[0087] Optionally, further parameters may be stored in the memory 38 to be read by the measurement electronics 20 .

[0088] For example, memory 38 may store a coefficient of variation of the relationship between the capacitance of probe 26 and the level of fuel 18 in tank 10 or the percentage of fill of tank 10 as a function of temperature, or any other relevant data, in order to adjust the accuracy of the measurements made by sensor 24 .

[0089] Alternatively, where the sensor 24 includes multiple probes 26 , such as a level meter and a density meter, the memory 38 may include values ​​for calibration parameters for each probe 26 .

[0090] The measuring electronics 20 are configured to calculate a measurement of the amount and / or density of the fuel 18 in the tank 10 based on the measured capacitance of the probe 26 and the value of the calibration parameter. The calculation is performed, for example, by linear interpolation.

[0091] The probe 26 is connected to the measurement electronics 20 via a communication bus that provides a connection of only two wires, a data line and a ground line. Such a communication bus is of the "single-wire" type, also known as the "Dallas bus". Such a communication bus allows a two-wire electrical connection.

[0092] According to the example presented, the two-wire electrical connection is coaxial, comprising a high impedance central core 42 and a shield radially surrounding the central core and a low impedance wire 47. Such a connection is Figure 2 This is schematically represented by a ground line 40 and a data line 42 connected to the inner electrode 30 of the sensor 24 .

[0093] Such a "single-wire" communication bus allows digital communication to occur by multiplexing on the same conductors used to transmit analog signals related to the measurements of the probe 26 without degrading these signals.

[0094] A terminal block 44 is disposed downstream of the wiring harness 22 , on the circuit board 34 , to allow connection of the probe 26 .

[0095] Thus, due to the multiplexing implemented in the measurement electronics 20 , the data stored in the memory 38 can be read by digital communication on the data line 42 .

[0096] Advantageously, the circuit board 34 may further comprise at least one resistor 45, which is connected in series to the input terminal of the memory 38. Thus, the resistor 45 provides a sufficient input resistance, for example of the order of 6 kilo-ohms.

[0097] The circuit board 34 may also include at least one diode 46 connected in parallel with the memory 38. This protects the memory 38 from potential overvoltages and improves the system's resistance to lightning strikes.

[0098] During operation, the measurement system 12 constitutes a data acquisition system in which the measurement electronics 20 are configured to:

[0099] - reading the data stored in the memory 38 at each start-up;

[0100] - detecting any changes in sensor 24; and / or

[0101] - If necessary, updating the values ​​of the calibration parameters stored in the memory 38 .

[0102] The memory 38 is read digitally, for example, over the data line 42, using a "single wire" communication protocol.

[0103] Once the reading of the data stored in the memory 38 has been completed, the memory 38 is isolated at the measuring electronics 20 .

[0104] The measuring electronics 20 then implements monitoring of the level or percentage or amount and / or density of the fuel 18 in the tank 10 via the probe 26. The capacitance value of the probe 26 thus measured is therefore established based on the values ​​of the calibration parameters previously retrieved, in order to accurately and reliably infer the amount and / or density of the fuel 18 present in the tank 10.

Claims

1. A sensor (24) for measuring at least one of the amount and / or density of fuel (18) in an aircraft tank (10), comprising: - at least one probe (26) configured to measure at least one of the quantity and / or density of the fuel, intended to be arranged in the interior space (16) of the tank (10); a memory (38), in particular an electrically erasable programmable read-only memory, arranged in the interior space (16) and configured to store at least some values ​​of calibration parameters of the probe (26); as well as A single communication bus, in particular composed of at least two conductors, is intended to connect the probe (26) and the memory (38) to the remote measurement electronics (20) via a wiring harness (22) passing through the wall (14) of the tank (10).

2. The sensor (24) according to claim 1, characterized in that The probe (26) is a level gauge, in particular a capacitance measuring level gauge, comprising two electrodes respectively connected to a low impedance conductor (47) and a high impedance conductor (42) of a communication bus protected by a shielding layer (40).

3. The sensor (24) according to claim 2, characterized in that The memory (38) is connected between the high impedance conductor (42) and the shield (40) of the communication bus.

4. The sensor (24) according to any of the preceding claims, comprising at least one diode (46) connected in parallel with the memory (38) and / or at least one resistor (45) connected in series with the memory (38).

5. The sensor (24) according to any one of the preceding claims, characterized in that The memory (38) is mounted on a printed circuit board (34) placed in a housing (36) located within the interior space (16) of the fuel tank (10).

6. The sensor (24) according to any one of the preceding claims, characterized in that The values ​​of the calibration parameters include two capacitance values ​​of the probe (26) measured at two different fill percentages of the tank (10).

7. The sensor (24) according to any one of the preceding claims, characterized in that The probe (26) is a densitometer consisting of two windings forming a transformer connected to an excitation circuit.

8. The sensor (24) according to any one of the preceding claims, characterized in that The sensor (24) also includes a temperature measuring probe.

9. An assembly comprising a fuel tank (10) and a measuring system (12), said measuring system comprising at least: - A sensor (24) according to any one of the preceding claims, - control electronics (20), and A wiring harness (22) extending between the sensor (24) and the control electronics (20), in particular through the wall (14) of the tank (10).

10. Method for measuring at least one of the amount and / or density of fuel (18) in a tank (10), using a sensor (24) according to any one of claims 1 to 8, and measuring electronics (20) connected to the sensor (24), the measuring method comprising at least: - an acquisition step during which at least one value of a calibration parameter of the probe (26) is acquired; - a storage step during which the values ​​of the calibration parameters are stored in a memory (38); a reading step during which the value of the calibration parameter is read from the memory (38) by the measuring electronics (20) each time the measuring electronics (20) is started; and - an acquisition step for acquiring a measurement of the amount and / or density of the fuel (18), during which the measurement electronics (20) acquires a measurement of the amount and / or density of the fuel (18) by using the probe (26) with the aid of the values ​​of the calibration parameters.

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