Digital measurement system for test bench

Abstract

This document relates to a digital measurement system (2) for an aircraft engine test bench, said digital measurement system (2) being configured to measure a physical parameter and comprising: at least one digital probe (6) having a printed circuit board (8) which includes: a substrate comprising a base (8a) and a head (8b), at least one digital sensor (6a-1, 6a-2, 6a-3, 6a-4) for measuring the physical parameter of the engine bench arranged on the head (8b) of the printed circuit board (8); and a first electrical signal transformer (6c) arranged on the base (8a) and electrically connected to said at least one digital sensor (6a-1, 6a-2, 6a-3, 6a-4) by a first communication bus (10-1); and an acquisition unit (4), which includes: a second electrical signal transformer (4b) electrically connected to the first electrical signal transformer (6c) by a second communication bus (10-2). Figure from the summary: Figure 1.

Description

Title of the invention: Digital measurement system for test bench. Technical field

[0001] This document relates to a digital measurement system, for example of temperature, usable with a test bench for turbofans or propulsion system modules, the test bench comprising a channel for a fluid and the digital measurement system comprising at least one digital probe disposed at least partially in said channel. Previous technique

[0002] It is known from the prior art the use of devices for measuring the temperature of a fluid in a test environment of an engine or module (partial tests, for example of a compressor) for aircraft, the devices being able to include sensors for measuring a physical parameter.

[0003] For example, in the case of temperature sensors, the fluid whose temperature is to be measured can be, for example: air, oil, kerosene.

[0004] The temperature sensors generally used are thermocouple probes or PT100 resistance probes.

[0005] Thermocouple probes have low measurement accuracy.

[0006] PT100 probes are based on the principle of resistance variation The electrical resistance of a material, in this case platinum, as a function of temperature. In operation, the resistance of platinum increases linearly with increasing temperature.

[0007] By measuring the electrical resistance of the PT 100 probe, the temperature to which it is exposed can be determined. This measurement can be performed using a suitable measuring circuit that converts the resistance into a temperature value, the information then being sent in the form of an analog signal.

[0008] In order to condition the analog signal, several electronic components are connected to the PT 100 probes (in particular to compensate for the variation in resistance of the wires which can also vary depending on the temperature).

[0009] It has been observed that the electronic components to which the thermocouples or PT100 probes for conditioning are connected are a major additional source of temperature uncertainty. Indeed, the information transmission chain adds further uncertainty to the measured temperature, in addition to the uncertainty inherent in the thermocouple or PT100 probe.

[0010] Another problem related to the connection was also observed. Although thermocouples or PT 100 probes have small dimensions (on the order of a few millimeters or even several tens of millimeters), their integration with electronic components implies a large volume of connecting cables, particularly in the case where several measurement points are required.

[0011] This is all the more true in the case of temperature measurements carried out by several thermocouples or PT 100 probes simultaneously, the number of peripherals increasing tenfold the volume of the necessary connectors (dimensions of the wiring, cable passage, etc.).

[0012] The test environment in which these measurements are deployed imposes significant distances (on the order of several tens of meters) between the temperature probes performing the measurements and an acquisition unit to which the data relating to the measurements must be routed, even though the location of the measurement is reduced.

[0013] There is therefore a need to miniaturize and reduce the intrusive aspect of measuring devices. Summary

[0014] To this end, the present document proposes a digital measurement system for an aircraft engine test bench comprising a channel for a fluid, said digital measurement system being capable of measuring a physical parameter of the fluid in the channel and comprising:

[0015] - at least one digital probe capable of being at least partially disposed in the fluid channel, said at least one digital probe comprising:

[0016] — a printed circuit board, which printed circuit board comprises:

[0017] — a substrate comprising a base and a head extending from said base;

[0018] — at least one digital sensor for measuring the physical parameter, preferably of the microelectromechanical system (MEMS) type, said system having at least one digital sensor arranged on the printed circuit board head; and

[0019] — a first electrical signal transformer arranged on the base and connected electrically audit at least one digital sensor via a first communication bus; and

[0020] - an acquisition unit, which comprises:

[0021] — a second electrical signal transformer electrically connected to first electrical signal transformer by a second communication bus, the second communication bus enabling the transmission of information between the first electrical signal transformer and the second electrical signal transformer; and

[0022] — an acquisition device electrically connected with said second electrical signal transformer via a third communication bus.

[0023] Digital sensors of the microelectromechanical system type, MEMS, make it possible to reduce the intrusive nature, which is particularly suitable for the environment of an engine test bench.

[0024] During operation, measurement data for the physical parameter of the test bench are acquired and then digitized by said at least one digital sensor. This digital data is then encapsulated in a frame, and an electrical signal carrying this frame is emitted by said at least one digital sensor.

[0025] The electrical signal then follows the following path: it travels through the first communication bus, the first electrical signal transformer, the second communication bus, the second electrical signal transformer, the third communication bus and arrives at the acquisition device.

[0026] When considering the transmission chain as a whole (from said at least one digital sensor to the acquisition device), the printed circuit board makes it possible to reduce the size related to the connectors.

[0027] Furthermore, the digital communication protocol of the digital measurement system allows: - multiplexing of electrical signals from digital sensors through the first electrical signal transformer and onto a single communication bus, the second communication bus, and - a multiplexing of the electrical signals from the digital probes through the second electrical signal transformer onto a single communication bus, the third communication bus.

[0028] In other words, the first electrical signal transformer is shared with the corresponding digital sensors, and the second electrical signal transformer is shared with the digital probes.

[0029] In other words, the printed circuit board allows the integration of a large number of components for a greatly limited number of cables.

[0030] This results, in addition to the limited size, in easier assembly.

[0031] Furthermore, the volume occupied by the connectors remains essentially constant regardless of the number of digital sensors or probes used. Measurement redundancy can therefore be achieved, or the number of measurement points can be multiplied without having to worry about the resulting bulk.

[0032] The arrangement of the elements of said at least one printed circuit board on the base or the head of the substrate (surface mount) allows positioning with a tolerance of ±0.025 mm: the use of a printed circuit board therefore also offers precise positioning of a digital sensor.

[0033] Furthermore, no additional uncertainty is added to the measurement of the physical parameter by the transmission chain, the data being digitized by said at least one digital sensor.

[0034] The second communication bus can also supply power to said at least one instrumentation comb.

[0035] The printed circuit board substrate may have a thickness between 0.12mm and 1.6mm, or between 0.2mm and 0.8mm, preferably equal to 0.8mm.

[0036] The printed circuit board of said at least one digital probe may be coated with a tropicalizing varnish. This protects the printed circuit board from humidity, dust, chemical contaminants, and temperature variations.

[0037] The physical parameter may be any one or a combination of the following parameters: pressure, temperature, humidity, fluid acceleration, vibration or gas composition.

[0038] The first communication bus allows the transmission of information between said at least one digital sensor and the first electrical signal transformer.

[0039] The second communication bus allows the transmission of information between the first electrical signal transformer and the second electrical signal transformer.

[0040] The third communication bus allows the transmission of information between the second electrical signal transformer and the acquisition device.

[0041] According to a particular embodiment, the physical parameter can be the temperature.

[0042] In other words, said at least one digital sensor may be at least one digital temperature sensor. In this case, it is capable of providing digital temperature measurement data, which meets a current need for aircraft engine test benches.

[0043] The first electrical signal transformer may be able to convert an electrical signal using an I2C (“Inter-Integrated Circuit” in English) communication protocol and circulating in the first communication bus into an electrical signal using a CANI2C layer and circulating in the second communication bus.

[0044] The second electrical signal transformer may be capable of converting an electrical signal using a CANI2C layer and circulating in the second communication bus into an electrical signal using an I2C communication protocol and circulating in the third communication bus.

[0045] In other words, the first communication bus and the third communication bus can use an I2C communication protocol, and the second communication bus can use a CANI2C layer.

[0046] According to this particular configuration, the electrical signal emitted by said at least one digital sensor and routed in the first communication bus uses an I2C communication protocol. This I2C communication protocol allows the sending of frames specific to the needs of the temperature measurement performed.

[0047] For example, it allows, through the sending of said frames, the transmission of an average value, a setting of the confidence interval, a setting of the sampling frequency, an average of the acquired data, etc.

[0048] The I2C communication protocol includes an SCA signal (“Serial Clock”) and an SDL signal (“Serial Data Line”).

[0049] This I2C communication protocol is particularly suited to a printed circuit board (simplicity of wiring, space saving, ease of integration ...).

[0050] However, the physical layer of this I2C protocol is not suitable for distances between devices on the order of several meters or tens of meters, unlike a physical layer of the CAN protocol.

[0051] The CAN (Controller Area Network) protocol is a serial communication protocol: bits are sent one after the other over a single communication link, unlike parallel communication, for example, where bits are sent simultaneously over several wires. In other words, the CAN serial communication protocol uses a single pair of wires to send data bits successively.

[0052] Still in this particular configuration, the first electrical signal transformer receives the SDA and SCL signals routed by the first communication bus using the I2C communication protocol.

[0053] Then, to carry each of the SDA and SCL signals over significant distances (on the order of several meters, to several tens of meters), the first electrical signal transformer can convert (transform) said signals into signals using a CANI2C layer.

[0054] By CANI2C layer, we mean a layer comprising a physical layer of the CAN protocol as well as a link layer and higher layers of the I2C protocol.

[0055] More specifically, the CANI2C layer refers to a dual CAN communication bus in the form of a twisted pair. In other words, it refers to a first CAN communication bus carrying the SDA signal, and a second CAN communication bus carrying the SCL signal.

[0056] In other words, by CANI2C layer, we mean a CANI2C physical layer.

[0057] The first electrical signal transformer allows the I2C communication bus of the received SDA and SCL signals to be extended into a first and second CAN communication bus, each CAN communication bus being associated with a signal.

[0058] The electrical signal carried in the second communication bus (from the first electrical signal transformer to the second electrical signal transformer) therefore uses this CANI2C layer.

[0059] The CAN physical layer allows the electrical signal to be routed over long distances (several tens of meters) from the first electrical signal transformer to the second electrical signal transformer, and also offers the advantage of being robust and able to operate in temperature and vibration conditions specific to a test environment, such as an aircraft engine test bench.

[0060] In this particular configuration, the electrical signal routed in the third communication bus (from the second electrical signal transformer to the acquisition device) uses an I2C communication protocol.

[0061] The second electrical signal transformer performs the inverse operation of the first electrical signal transformer: the electrical signal returns to its initial state emitted by said at least one digital sensor. In this way, it can be used by the acquisition device. Thus, the CAN layer becomes transparent, because the digital frame from the sensor is restored in I2C.

[0062] In one aspect, the digital probe may comprise a single digital sensor. In this way, one overcomes the limitations imposed on electronic components allowing for a plurality of digital sensors (for example, limitations on operating temperature).

[0063] Said at least one digital sensor may comprise a plurality of digital sensors, said printed circuit comprising a switching device arranged on the base of the printed circuit, the switching device being electrically connected to the first electrical signal transformer on the one hand, and to the plurality of digital sensors on the other hand.

[0064] The switching device can be arranged on the printed circuit board basis in closer proximity to the plurality of digital sensors than the first electrical signal transformer.

[0065] In this way, the electronic components (the digital sensors, the switching device and the first electrical signal transformer) are arranged in an optimized manner for signal pathing.

[0066] The switching device may include a plurality of address translators, each address translator being electrically connected to a respective digital sensor.

[0067] In the case of a switching device comprising a plurality of address translators, each address translator can be electrically connected to said first electrical signal transformer, on the one hand, and to a respective digital sensor, on the other hand.

[0068] In other words, the address translator can be arranged between the plurality of digital sensors and the first electrical signal transformer.

[0069] In this particular configuration, each address translator is arranged on a respective first communication bus. In other words, each address translator splits the respective first communication bus into a primary first communication bus linking the address translator and the digital sensor, and a secondary first communication bus linking the address translator and the first electrical signal transformer.

[0070] Thus, the electrical signal coming out of the plurality of digital address translator sensors first passes through the plurality of address translators before arriving at the first electrical signal transformer.

[0071] The address translator is an integrated circuit whose role is to make each digital sensor appear under a different address. Thus, it is possible to integrate the same sensor multiple times in the probe or on the same network without being limited by address conflicts.

[0072] In other words, the plurality of address translators allows each digital sensor to have its own unique address.

[0073] The switching device may include a multiplexer, the multiplexer being electrically connected to the plurality of digital sensors by the first communication bus.

[0074] In the case of a plurality of digital sensors, the multiplexer allows communication with several peripherals (the digital sensors) via a single bus (the first communication bus) even if the peripherals have identical addresses.

[0075] In addition, the multiplexer makes it possible to reduce the number of components mounted on the printed circuit board: a single component (the multiplexer) is common to all of the plurality of digital sensors.

[0076] In other words, the multiplexer is shared by the plurality of digital sensors arranged on the plurality of pins of the printed circuit board and in the plurality of nozzles of the comb.

[0077] Additionally, the multiplexer ensures measurement reliability at any operating temperature specific to the environmental conditions of an engine test bench (including above 85°C).

[0078] Said at least one digital sensor may comprise a plurality of digital sensors and the printed circuit head may have a length, the plurality of digital sensors being distributed over the length of the head.

[0079] In this way, measurements of the physical parameter along the printed circuit board head can be carried out, for example, to establish a gradient, or to have an average over the length of the printed circuit board head.

[0080] Alternatively, the plurality of digital sensors can be distributed uniformly along the length of the head. In other words, the longitudinal spacing between each digital sensor can be identical.

[0081] Said at least one digital probe may include a protective housing in which the printed circuit board is housed, the protective housing having an end opening.

[0082] In this way, the printed circuit board (and more specifically the electronic components mounted on it) is protected by the protective housing. Furthermore, the end opening ensures that the digital sensors remain in contact with the fluid being measured.

[0083] The head can extend outward through the end opening of the housing so as to present at least one of the digital sensors protruding outside the housing.

[0084] In this configuration, said at least one digital sensor, at the level of an end portion of the printed circuit board head of said at least one digital probe, is outside the housing.

[0085] In this way, the response time is improved (i.e., reduced), since the protective housing no longer constitutes a physical obstacle between the fluid and said at least one digital sensor. For example, in the case of a digital temperature sensor, the response time is reduced by improving the heat propagation time.

[0086] In this case, we obtain response times of approximately 0.12 seconds.

[0087] The base may have a first thickness and the head may have a second thickness reduced compared to the first thickness, the head being flexible.

[0088] In other words, the second thickness can be less than the first thickness.

[0089] For example, the second thickness can be at least 8 times smaller than the first thickness.

[0090] The second thickness can be between 0.12 and 1.6 mm, or between 0.2 mm and 0.8 mm.

[0091] By making the printed circuit board head more flexible, the thickness of the printed circuit board head (second layer) can be reduced, which facilitates assembly. Furthermore, the reduced thickness limits thermal inertia and results in improved response time.

[0092] This document may relate to an aircraft engine test bench comprising the aforementioned digital measurement system, said test bench comprising the channel for a fluid in which said at least one digital probe is at least partially disposed.

[0093] This document may also relate to a method for measuring a physical parameter of a fluid in a channel of a test bench of the type described above, the method comprising the steps of: a. acquire digital data of the measured physical parameter using digital sensors; b. transmit to the first electrical signal transformer an initial electrical signal carrying said digital data via the first communication bus; c. convert said initial electrical signal into an intermediate electrical signal by means of the first electrical signal transformer so that the intermediate electrical signal is suitable for transmission from the first electrical signal transformer to the second electrical signal transformer; d. transmit said intermediate electrical signal from the first electrical signal transformer to the second electrical signal transformer via the second communication bus; e. convert said intermediate electrical signal into a final electrical signal by means of the second electrical signal transformer so that the final electrical signal is suitable for use by the acquisition device; f. transmit said final electrical signal from the second electrical signal transformer to the acquisition device via the third communication bus; and g. acquire a frame carried by the final electrical signal by means of the acquisition device. Brief description of the drawings

[0094] Other features, details and advantages will become apparent upon reading the detailed description below, and upon analysis of the accompanying drawings, on which:

[0095] [Fig-1] schematically illustrates the architecture of a digital measurement system comprising a single digital probe, according to a first embodiment of this document,

[0096] [Fig.2] is a schematic view of a digital probe according to the embodiment of [Fig.1],

[0097] [Fig.3] schematically illustrates the architecture of a digital measurement system comprising a plurality of digital probes, according to a second embodiment of this document,

[0098] [Fig.4] is a schematic view of a digital probe according to the second embodiment of [Fig.3],

[0099] [Fig.5] schematically illustrates the architecture of a digital measurement system comprising a plurality of digital probes, according to a third embodiment of this document,

[0100] [Fig.6] is a schematic view of a digital probe according to the third embodiment of [Fig.5],

[0101] [Fig.7] schematically illustrates a digital probe according to a fourth embodiment of this document,

[0102] [Fig.8] schematically illustrates a digital probe according to a fifth embodiment of this document,

[0103] [Fig.9] schematically illustrates a digital probe according to a sixth embodiment of this document, and

[0104] [Fig. 10] is a diagram of the temperature error as a function of the temperature measured by the digital measuring system, extracted from a technical documentation of a Texas Instruments® brand digital temperature sensor and reference TMP117. Description of the implementation methods

[0105] [Fig.1] represents a digital measuring system 2 according to a first embodiment of this document in which the digital measuring system 2 comprises a single digital probe 6, and [Fig.2] represents in detail said digital probe 6.

[0106] The digital probe 6 includes a protective housing 6e in which is housed a printed circuit 8 which includes a substrate, said substrate having a base 8a and a head 8b.

[0107] The base 8a comprises a length L1 less than a length L2 of the head 8b, and a thickness el, called the first thickness, greater than a thickness e2 of the head 8b, called the second thickness.

[0108] A single digital sensor 6a-l is arranged on a longitudinal end 8c of the head 8b.

[0109] For example, in the case of digital temperature sensors, the 6a-1 digital sensor and the digital sensors described later in this section may be of the Texas Instruments® brand and reference TMP117.

[0110] The embodiments described in the remainder of this section relate to temperature measurement. However, it should be understood that other physical parameters distinct from temperature can be measured.

[0111] A first electrical signal transformer 6c is arranged on a first end 8d of the base 8a opposite the longitudinal end 8c of the head 8b.

[0112] For example, the first electrical signal transformer 6c may be of the brand ANALOG DEVICES® and of reference LT3960.

[0113] The digital sensor 6a-1 is connected to the first electrical signal transformer 6c by a first communication bus 10-1.

[0114] An acquisition unit 4 comprises an acquisition device 4a and a second electrical signal transformer 4b.

[0115] For example, the second electrical signal transformer 4b may be of the brand ANALOG DEVICES® and of reference LT3960.

[0116] The first electrical signal transformer 6c is connected to the second electrical signal transformer 4b by a second communication bus 10-2.

[0117] In operation, the digital sensor 6a-l measures the temperature of a fluid with which the digital probe 6 is in contact.

[0118] The digital data relating to the measured temperature are encapsulated in frames which are transported by an initial electrical signal emitted which uses an I2C communication protocol.

[0119] The initial electrical signal from the digital sensor 6a-1 travels in the first communication bus 10-1 and arrives at the first electrical signal transformer 6c.

[0120] The first electrical signal transformer 6c then converts the initial electrical signal into an intermediate electrical signal, the latter being able to circulate in a layer called the CANI2C layer (physical layer according to the CAN protocol and link layer and upper layers defined by the I2C communication protocol).

[0121] In this way, the intermediate electrical signal is able to be routed over the distance separating the first electrical signal transformer 6c from the second electrical signal transformer 4b through a second communication bus 10-2. In other words, the intermediate electrical signal is able to flow from the digital probe 6 to the acquisition unit 4.

[0122] The second electrical signal transformer 4b then converts the intermediate electrical signal into a final electrical signal using an I2C communication protocol. In other words, the second electrical signal transformer 4b performs the reverse conversion (the inverse operation) to the first electrical signal transformer 6c.

[0123] In this way, the final electrical signal can be used by the acquisition device 4a, which is in the same acquisition unit 4 as the second electrical signal transformer 4b (and therefore adjacent to it). The final electrical signal travels in the third communication bus 10-3 from the second electrical signal transformer 4b to the acquisition device 4a.

[0124] The first communication bus 10-1 and the third communication bus 10-3 use an I2C communication protocol, and the second communication bus, arranged between the first and third communication buses 10-1, 10-3, uses the CANI2C layer.

[0125] Reference is now made to figures 3 and 4 which represent the digital measurement system according to a second embodiment of this document.

[0126] In this second embodiment, the digital measurement system 2 comprises N digital probes 6-1, 6-N all connected to the acquisition unit 4 by the second communication bus 10-2.

[0127] In addition, each digital probe 6-1, 6-N comprises four digital sensors 6a-1, 6a-2, 6a-3, 6a-4. [Fig.4] shows in detail the digital probe 6-1 (identical to the other digital probes).

[0128] Each digital probe 6-1, 6-N includes a switching device 5 arranged on the base 8a.

[0129] In this second embodiment, for each digital probe 6-1, 6-N, the switching device 5 comprises four address translators 6b-1, 6b-2, 6b-3, 6b-4.

[0130] The four digital sensors 6a-1, 6a-2, 6a-3, 6a-4 are arranged on the longitudinal end 8c of the head 8b and the four address translators 6b-1, 6b-2, 6b-3, 6b-4 are arranged on the base 8a, at a second proximal end 8e of the head 8b and opposite to the first end 8d.

[0131] The four address translators 6b-1, 6b-2, 6b-3, 6b-4 are arranged on the first communication bus 10-1.

[0132] In other words, the four address translators 6b-1, 6b-2, 6b-3, 6b-4 are arranged between the digital sensors 6a-1, 6a-2, 6a-3, 6a-4 and the first electrical signal transformer 6c so that each address translator 6b-1, 6b-2, 6b-3, 6b-4 is connected to a respective digital sensor 6a-1, 6a-2, 6a-3, 6a-4, on the one hand, and to the first electrical signal transformer 6c, on the other hand.

[0133] In operation, the four digital sensors 6a-1, 6a-2, 6a-3, 6a-4 of each digital probe measure the temperature of a fluid with which the digital probes 6-1, 6N are in contact.

[0134] For each digital sensor 6a-1, 6a-2, 6a-3, 6a-4, the digital data relating to the measured temperature are encapsulated in frames which are transported by an initial electrical signal emitted which uses an I2C communication protocol.

[0135] The initial electrical signals from each digital sensor 6a-1, 6a-2, 6a-3, 6a-4 travel in the first respective communication bus 10-1: they first pass through the respective address translator 6b-1, 6b-2, 6b-3, 6b-4 and then converge towards the first electrical signal transformer 6c.

[0136] The address translators 6b-1, 6b-2, 6b-3, 6b-4 associate with each digital sensor 6a-1, 6a-2, 6a-3, 6a-4 an address which is specific to them.

[0137] The address translators 6b-1, 6b-2, 6b-3, 6b-4 prevent an address conflict between the different digital sensors 6a-1, 6a-2, 6a-3, 6a-4. In this way, it is possible to distinguish the digital sensors from each other, particularly at the level of the acquisition unit 4.

[0138] The first electrical signal transformer 6c then converts the initial electrical signals into an intermediate electrical signal, the latter using the CANI2C layer.

[0139] The routing of the intermediate electrical signal to the acquisition unit 4 is then similar to that described in [Fig.1].

[0140] The second embodiment has the advantage of performing:

[0141] - a multiplexing of the initial electrical signals from the four digital sensors 6a-1, 6a-2, 6a-3, 6a-4 on a single communication bus, the second communication bus 10-2, and

[0142] - a multiplexing of the intermediate electrical signals of the N digital probes 6-1, 6-N on a single communication bus, the third communication bus 10-3.

[0143] Figures 4 and 5 represent a third embodiment which is a variant of the second embodiment.

[0144] According to this third embodiment, the switching device 5 of each digital probe 6-1, 6-N includes a multiplexer 6b'.

[0145] For a probe, the multiplexer 6b' is arranged between the digital sensors 6a-1, 6a-2, 6a-3, 6a-4 and the first electrical signal transformer 6c so as to be electrically connected to the digital sensors 6a-1, 6a-2, 6a-3, 6a-4, on the one hand, and to the first electrical signal transformer 6c, on the other hand.

[0146] For example, the 6b' multiplexer may be of the Texas Instruments® brand and reference TCA9548APWR.

[0147] In operation, the acquisition unit 4 commands the multiplexer 6b' to activate only one input (only one of the digital sensors 39 among the plurality) in order to avoid an address conflict.

[0148] It can be seen that the use of a 6b' multiplexer makes it possible to reduce the number of components and associated connectors required for the operation of the digital probe (and therefore for the operation of the digital measurement system 2 if we look at the whole),

[0149] Reference is now made to [Fig.7] which schematically illustrates a probe digital according to a fourth embodiment of this document.

[0150] In this particular configuration, the head 8b of the printed circuit board 8 is flexible, which allows it to have a reduced thickness e3 (in particular less than e2).

[0151] A digital sensor 6a-1 is arranged at the end 8c of the head 8b.

[0152] The response time is proportional to the thickness of the printed circuit board in which the An electrical signal flows (i.e., the head 8b and the base 8a). In operation, the reduced thickness of the head 8b then allows for a better response time.

[0153] Furthermore, the digital probe 6 includes a connector 7 attached to the protective housing 6e and arranged against the first end 8d of the base 8a of the printed circuit board 8. The connector 7 is connected to the printed circuit board, on the one hand, and to connecting wires 18 (equivalent to the second communication bus 10-2), on the other hand.

[0154] Connector 7 provides power to the printed circuit board 8 and transmits the electrical signal.

[0155] Reference is now made to [Fig.8] which schematically illustrates a digital probe according to a fifth embodiment of this document.

[0156] In this particular configuration, five digital sensors 6a-1, 6a-2, 6a-3, 6a-4, 6a-5 are distributed along the length of the head 8b of the printed circuit board and are connected to five address translators 6b-1, 6b-2, 6b-3, 6b-4, 6b-5 arranged on the second end 8e of the base 8a.

[0157] The digital sensor 6a-5 is arranged at the end 8c of the head 8b.

[0158] In operation, the five digital sensors 6a-1, 6a-2, 6a-3, 6a-4, 6a-5 allow temperature measurements along head 8b, and to establish, for example, an average over the length of head 8b or a temperature gradient.

[0159] Reference is now made to [Fig.9] which schematically illustrates a probe digital according to a sixth embodiment of this document.

[0160] In this particular configuration, the protection housing 6e of the digital probe includes a head 6e-1 surrounding the head 8b of the printed circuit 8, said head 6e-1 having an opening 9 at a longitudinal end.

[0161] The printed circuit board head 8b extends longitudinally through the opening 9 and opens onto the outside of the protective housing 6e.

[0162] A digital sensor 6a-1 is arranged on the end 8c of the head 8b of the printed circuit board 8 and is also arranged outside the protective housing 6e.

[0163] In operation, the fluid, whose temperature is measured, is in direct contact with said digital sensor 6a-1, which allows a better heat propagation time (i.e. a reduced propagation time), and therefore a better response time.

[0164] Reference is now made to [Fig. 10], which is a diagram of the temperature error (i.e. uncertainty) as a function of the temperature measured by the digital measuring system.

[0165] The diagram is taken from technical documentation for a Texas Instruments® brand digital temperature sensor, reference TMP117.

[0166] The positive temperature error is represented by the curve Cl and the negative temperature error is represented by the curve C2.

[0167] It is observed that the maximum error over the temperature range measured between -20°C and 50°C is ±0.1 °C.

[0168] The maximum error over the measured temperature range between -40°C and 70°C is ± 0.15 °C.

[0169] The maximum error over the measured temperature range between -40°C and 100°C is ± 0.2 °C.

[0170] The maximum error over the temperature range measured between -55°C and 125°C (up to 150°C) is ± 0.25°C.

[0171] These errors (or uncertainties) are satisfactory for temperature measurements in a test environment such as an aircraft engine test bench which typically operates within the temperature ranges represented.

[0172] It is to be understood that the errors illustrated take into account the entire transmission chain of the digital system for measuring the temperature of the fluid in the channel, that is to say the transmission chain from the digital sensor to the acquisition unit.

[0173] Taking this consideration into account, it is observed that the uncertainties are reduced compared to conventional solutions of the prior art.

[0174] In operation, the digital sensor communicates the value of the measured physical parameter directly in digital format, which offers greater reliability compared to analog signals, which can be subject to interference, particularly in bench systems or in environments with hybrid machines (motors).

[0175] With degradation over time or through the different stages of transmission, digital signals do not suffer from these problems.

[0176] A digital signal is transmitted in the form of bits; it is either completely transmitted or not transmitted, which eliminates uncertainties related to fluctuations, distortions, etc. of the signal, which are frequent with analog transmissions.

[0177] On the other hand, digital signals are not affected by drift, which is an undesirable variation of the analog signal due to factors such as temperature or wear of components and the acquisition system. Therefore, the transmitted information remains precise and faithful to the original value measured by the digital sensor (sequence of 0s and 1s).

[0178] The digital nature of the digital sensor (particularly in the case of MEMS sensors) therefore allows for more precise and reliable data transmission from the sensor output.

Claims

Demands

1. A digital measurement system (2) for an aircraft engine test bench comprising a channel for a fluid, said digital measurement system (2) being capable of measuring a physical parameter of the fluid in the channel and comprising: - at least one digital probe (6) capable of being at least partially disposed in the fluid channel, said at least one digital probe (6) comprising: — a printed circuit board (8), said printed circuit board (8) comprising: — a substrate comprising a base (8a) and a head (8b) extending from said base (8a); — at least one digital sensor (6a-1, 6a-2, 6a-3, 6a-4) for measuring the physical parameter, preferably of the microelectromechanical system, MEMS type, said at least one digital sensor (6a-1, 6a-2, 6a-3, 6a-4) being arranged on the head (8b) of the printed circuit board (8);and — a first electrical signal transformer (6c) arranged on the base (8a) and electrically connected to said at least one digital sensor (6a-1, 6a-2, 6a-3, 6a-4) by a first communication bus (10-1); and — an acquisition unit (4), which comprises: — a second electrical signal transformer (4b) electrically connected to the first electrical signal transformer (6c) by a second communication bus (10-2), the second communication bus (10-2) enabling the transmission of information between the first electrical signal transformer (6c) and the second electrical signal transformer (4b); and — an acquisition device (4a) electrically connected to said second electrical signal transformer (4b) by a third communication bus (10-3).

2. Digital measuring system (2) according to claim 1, wherein the physical parameter is temperature.

3. A digital measurement system (2) according to any one of the preceding claims, wherein the first electrical signal transformer (6c) is capable of converting an electrical signal using an I2C communication protocol and circulating in the first communication bus (10-1) into an electrical signal using a layer CANI2C and circulating in the second communication bus (10-2), and the second electrical signal transformer (4b) is capable of converting an electrical signal using a CANI2C layer and circulating in the second communication bus (10-2) into an electrical signal using an I2C communication protocol and circulating in the third communication bus (10-3).

4. Digital measuring system (2) according to any one of the preceding claims, wherein said at least one digital sensor (6a-1) comprises a plurality of digital sensors (6a-1, 6a-2, 6a-3, 6a-4), said printed circuit board (8) comprising a switching device (5) arranged on the base (8a) of the printed circuit board (8), the switching device (5) being electrically connected to the first electrical signal transformer (6c) on the one hand, and to the plurality of digital sensors (6a-1, 6a-2, 6a-3, 6a-4) on the other hand.

5. Digital measuring system (2) according to claim 4, wherein the switching device (5) comprises a plurality of address translators (6b-1, 6b-2, 6b-3, 6b-4), each address translator (6b-1, 6b-2, 6b-3, 6b-4) being electrically connected to a respective digital sensor (6a-1, 6a-2, 6a-3, 6a-4).

6. Digital measurement system (2) according to claim 4, wherein the switching device (5) comprises a multiplexer (6b'), the multiplexer (6b') being electrically connected to the plurality of digital sensors (6a-1, 6a-2, 6a-3, 6a-4) by the first communication bus (10-1).

7. Digital measuring system (2) according to any one of the preceding claims, wherein said at least one digital sensor (6a-1) comprises a plurality of digital sensors (6a-1, 6a-2, 6a-3, 6a-4, 6a-5) and the head (8b) of the printed circuit board (8) has a length (L2), the plurality of digital sensors (6a-1, 6a-2, 6a-3, 6a-4, 6a-5) being distributed over the length (L2) of the head (8b).

8. Digital measuring system (2) according to any one of the preceding claims, wherein said at least one digital probe (6) comprises a protective housing (6e) in which the printed circuit board (8) is housed, the protective housing (6e) comprising an end opening (9).

9. A digital measuring system (2) according to the preceding claim, wherein the head (8b) extends projecting through the opening

10. end (9) of the protective housing (6e) so as to present at least one of the digital sensors (6a-1, 6a-2, 6a-3, 6a-4) protruding outside the protective housing (6e). Digital measuring system (2) according to any one of the preceding claims, wherein the base (8a) has a first thickness (el) and the head (8b) has a second thickness (e2) reduced in relation to the first thickness, the head (8b) being flexible.

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