Digital measuring system for a test bench

Abstract

The present document relates to a digital measuring system (2) for an aircraft engine test bench, the digital measuring system (2) being configured to measure a physical parameter and comprising: at least one digital probe (6) comprising a printed circuit board (8) that comprises: a substrate comprising a base (8a) and a top (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 top (8b) of the printed circuit board (8); and a first electrical signal transformer (6c) arranged on the base (8a) and electrically connected to the 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) that comprises: a second electrical signal transformer (4b) electrically connected to the first electrical signal transformer (6c) by a second communication bus (10-2).

Description

Description Title: 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 prior art to use 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 the variation of a material's electrical resistance, 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 PT100 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, with the information then being sent as an analog signal.

[0008] In order to condition the analog signal, several electronic components are connected to the PT100 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 thermocouples or PT100 probes are connected for conditioning are a major additional source of temperature uncertainty. Indeed, the information transmission chain adds further uncertainty to the measured temperature, in addition to the inherent uncertainty of the thermocouple or PT100 probe.

[0010] Another problem related to connectivity was also observed. Although thermocouples or PT100 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 when several measurement points are required.

[0011] This is especially true in the case of temperature measurements carried out by several thermocouples or PT100 probes simultaneously, the number of devices increasing tenfold the volume of the necessary connections (dimensions of the wiring, cable routing, 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] Therefore, there is a need to miniaturize and reduce the intrusive aspect of measurement devices. Summary

[0014] To this end, this 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: - at least one digital probe capable of being at least partially disposed in the fluid channel, said at least one digital probe comprising: - a printed circuit board, which printed circuit board comprises: — a substrate comprising a base and a head extending from said base; — at least one digital sensor for measuring the physical parameter, preferably of the microelectromechanical system (MEMS) type, said at least one digital sensor being arranged on the printed circuit board head; and — a first electrical signal transformer arranged on the base and electrically connected to said at least one digital sensor via a first communication bus; and - an acquisition unit, which includes: - a second electrical signal transformer electrically connected to the 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 - an acquisition device electrically connected to said second electrical signal transformer by a third communication bus.

[0015] Digital sensors of the microelectromechanical system (MEMS) type reduce intrusiveness, making them particularly suitable for the environment of an engine test bench.

[0016] 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.

[0017] The electrical signal then follows this path: it travels through the first communication bus, the first electrical signal transformer, the second communication bus, the second electrical signal transformer, third communication bus and arrives at the acquisition device.

[0018] 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 space required for the connectors.

[0019] 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 multiplexing of electrical signals from digital probes through the second electrical signal transformer onto a single communication bus, the third communication bus.

[0020] 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.

[0021] In other words, the printed circuit board allows for the integration of a large number of components with a significantly limited number of cables.

[0022] This results, in addition to the limited size, in easier assembly.

[0023] Furthermore, the volume occupied by the connectors remains virtually constant regardless of the number of digital sensors or probes used. This allows for measurement redundancy or the multiplication of measurement points without having to worry about the resulting bulk.

[0024] 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.

[0025] 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.

[0026] The second communication bus can also supply power to at least one instrumentation comb.

[0027] The printed circuit board substrate can have a thickness between 0.12mm and 1.6mm, or between 0.2mm and 0.8mm, preferably equal to 0.8mm.

[0028] The printed circuit board of said at least one digital probe may be coated with a tropicalization varnish. This protects the printed circuit board from humidity, dust, chemical contaminants, and temperature variations.

[0029] The physical parameter can be any one or a combination of the following parameters: pressure, temperature, humidity, fluid acceleration, vibration, or gas composition.

[0030] The first communication bus enables the transmission of information between said at least one digital sensor and the first electrical signal transformer.

[0031] The second communication bus allows the transmission of information between the first electrical signal transformer and the second electrical signal transformer.

[0032] The third communication bus enables the transmission of information between the second electrical signal transformer and the acquisition device.

[0033] According to a particular embodiment, the physical parameter can be temperature.

[0034] In other words, at least one digital sensor can be a 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.

[0035] The first electrical signal transformer may be capable of converting an electrical signal using an I2C (Inter-Integrated Circuit) communication protocol and circulating in the first communication bus into an electrical signal using a CANI2C layer and circulating in the second communication bus.

[0036] 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.

[0037] 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.

[0038] In this particular configuration, the electrical signal emitted by at least one digital sensor and carried 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 being performed.

[0039] For example, it allows, through the sending of said frames, the emission of an average value, a setting of the confidence interval, a setting of the sampling frequency, an average of the acquired data, etc.

[0040] The I2C communication protocol includes an SCA signal (“Serial Clock”) and an SDL signal (“Serial Data Line”).

[0041] This I2C communication protocol is particularly suited to a printed circuit board (simplicity of wiring, space saving, ease of integration...).

[0042] 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.

[0043] The CAN (Controller Area Network) protocol is a serial communication protocol: bits are sent one after another over a single communication link, unlike parallel communication, for example, where bits are sent simultaneously over multiple wires. In other words, the CAN serial communication protocol uses a single pair of wires to send data bits sequentially.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] More specifically, the CANI2C layer refers to a dual CAN communication bus, in the form of a twisted pair. In other words, it consists of a first CAN communication bus carrying the SDA signal, and a second CAN communication bus carrying the SCL signal.

[0048] In other words, by CANI2C layer, we mean a CANI2C physical layer.

[0049] The first electrical signal transformer allows the I2C communication bus of 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.

[0050] 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.

[0051] The CAN physical layer allows the electrical signal to be carried 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.

[0052] In this particular configuration, the electrical signal carried in the third communication bus (from the second electrical signal transformer to the acquisition device) uses an I2C communication protocol.

[0053] The second electrical signal transformer performs the inverse operation of the first: the electrical signal returns to its initial state as emitted by at least one digital sensor. In this way, it can be used by the acquisition device. Thus, the CAN layer becomes transparent, as the digital frame from the sensor is converted back to I2C.

[0054] In one respect, the digital probe can consist of a single digital sensor. This overcomes the limitations imposed on electronic components that allow for multiple digital sensors (for example, limitations on operating temperature).

[0055] Said at least one digital sensor may comprise a plurality of digital sensors, said printed circuit board comprising a switching device arranged on the basis of the printed circuit board, 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.

[0056] The switching device can be arranged on the printed circuit board in closer proximity to the plurality of digital sensors than the first electrical signal transformer.

[0057] 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 paths.

[0058] The switching device may include a plurality of address translators, each address translator being electrically connected to a respective digital sensor.

[0059] 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.

[0060] In other words, the address translator can be arranged between the plurality of digital sensors and the first electrical signal transformer.

[0061] In this particular configuration, each address translator is arranged on its respective first communication bus. In other words, each address translator splits its respective first communication bus into a primary communication bus connecting the address translator and the digital sensor, and a secondary communication bus connecting the address translator and the first electrical signal transformer.

[0062] 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.

[0063] The address translator is an integrated circuit whose role is to assign a different address to each digital sensor. This allows the same sensor to be integrated multiple times within the probe or on the same network without being limited by address conflicts.

[0064] In other words, the plurality of address translators allows each digital sensor to have its own unique address.

[0065] The switching device may include a multiplexer, the multiplexer being electrically connected to the plurality of digital sensors by the first communication bus.

[0066] In the case of multiple digital sensors, the multiplexer allows communication with several devices (the digital sensors) via a single bus (the first communication bus) even if the devices have identical addresses.

[0067] 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.

[0068] 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.

[0069] Additionally, the multiplexer ensures measurement reliability at any operating temperature specific to the environmental conditions of an engine test bench (including above 85°C).

[0070] Said at least one digital sensor may comprise a plurality of digital sensors and the printed circuit board head may have a length, the plurality of digital sensors being distributed over the length of the head.

[0071] In this way, measurements of the physical parameter along the printed circuit board head can be taken, for example, to establish a gradient, or to have an average over the length of the printed circuit board head.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] In this way, the response time is improved (i.e., reduced), since the protective housing no longer constitutes a physical barrier between the fluid and the at least one digital sensor. For example, in the case of a digital temperature sensor, the response time is decreased by improving the heat propagation time.

[0078] In this case, we obtain response times of approximately 0.12 seconds.

[0079] 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.

[0080] In other words, the second thickness can be less than the first thickness.

[0081] For example, the second thickness can be at least 8 times less than the first thickness.

[0082] The second thickness can be between 0.12 and 1.6 mm, or between 0.2 mm and 0.8 mm.

[0083] By making the printed circuit board head more flexible, we can reduce its thickness (the second layer), which simplifies assembly. Furthermore, this reduced thickness limits thermal inertia and improves response time.

[0084] 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 is at least partially disposed said at least one digital probe.

[0085] 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

[0086] Other features, details, and advantages will become apparent upon reading the detailed description below and analyzing the attached drawings, on which:

[0087] [Fig. 1] schematically illustrates the architecture of a digital measurement system comprising a single digital probe, according to a first embodiment of this document,

[0088] [Fig. 2] is a schematic view of a digital probe according to the embodiment of Figure 1,

[0089] [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,

[0090] [Fig. 4] is a schematic view of a digital probe according to the second embodiment of Figure 3,

[0091] [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,

[0092] [Fig. 6] is a schematic view of a digital probe according to the third embodiment of Figure 5,

[0093] [Fig. 7] schematically illustrates a digital probe according to a fourth embodiment of this document,

[0094] [Fig. 8] schematically illustrates a digital probe according to a fifth embodiment of this document,

[0095] [Fig. 9] schematically illustrates a digital probe according to a sixth embodiment of this document, and

[0096] [Fig. 10] is a diagram of the temperature error as a function of the temperature measured by the digital measurement system, taken from a technical documentation of a Texas Instruments® brand digital temperature sensor, reference TMP117. Description of the implementation methods

[0097] Figure 1 represents a digital measurement system 2 according to a first embodiment of this document in which the digital measurement system 2 comprises a single digital probe 6, and Figure 2 represents in detail said digital probe 6.

[0098] 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.

[0099] The base 8a includes a length L1 less than a length L2 of the head 8b, and a thickness e1, called the first thickness, greater than a thickness e2 of the head 8b, called the second thickness.

[0100] A single digital sensor 6a-1 is arranged on a longitudinal end 8c of the head 8b.

[0101] 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 TMP1 17.

[0102] 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.

[0103] 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.

[0104] For example, the first 6c electrical signal transformer may be from the brand ANALOG DEVICES® and reference LT3960.

[0105] The digital sensor 6a-1 is connected to the first electrical signal transformer 6c by a first communication bus 10-1.

[0106] An acquisition unit 4 comprises an acquisition device 4a and a second electrical signal transformer 4b.

[0107] For example, the second electrical signal transformer 4b may be from the brand ANALOG DEVICES® and reference LT3960.

[0108] The first electrical signal transformer 6c is connected to the second electrical signal transformer 4b by a second communication bus 10-2.

[0109] In operation, the digital sensor 6a-1 measures the temperature of a fluid with which the digital probe 6 is in contact.

[0110] The digital data relating to the measured temperature are encapsulated in frames which are transported by an initial electrical signal emitted using an I2C communication protocol.

[0111] 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.

[0112] 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).

[0113] 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.

[0114] 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) of the first electrical signal transformer 6c.

[0115] 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.

[0116] The first 10-1 communication bus and the third 10-3 communication bus use an I2C communication protocol, and the second communication bus, arranged between the first and third 10-1, 10-3 communication buses, uses the CANI2C layer.

[0117] Reference is now made to figures 3 and 4 which represent the digital measurement system according to a second embodiment of this document.

[0118] 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.

[0119] In addition, each digital probe 6-1, 6-N includes four digital sensors 6a-1, 6a-2, 6a-3, 6a-4. Figure 4 shows in detail the digital probe 6-1 (identical to the other digital probes).

[0120] Each digital probe 6-1, 6-N includes a switching device 5 arranged on the base 8a.

[0121] 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.

[0122] 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.

[0123] The four address translators 6b-1, 6b-2, 6b-3, 6b-4 are arranged on the first communication bus 10-1.

[0124] 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.

[0125] 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.

[0126] 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.

[0127] The initial electrical signals from each digital sensor 6a-1, 6a-2, 6a-3, 6a-4 circulate 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.

[0128] Address translators 6b-1, 6b-2, 6b-3, 6b-4 associate each digital sensor 6a-1, 6a-2, 6a-3, 6a-4 with its own unique address.

[0129] Address translators 6b-1, 6b-2, 6b-3, 6b-4 prevent address conflicts 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 acquisition unit 4 level.

[0130] The first electrical signal transformer 6c then converts the initial electrical signals into an intermediate electrical signal, the latter using the CANI2C layer.

[0131] The routing of the intermediate electrical signal to the acquisition unit 4 is then similar to that described in Figure 1.

[0132] The second embodiment has the advantage of performing: - a multiplexing of the initial electrical signals from the four digital sensors 6a-1, 6a-2, 6a-3, 6a-4 onto a single communication bus, the second communication bus 10-2, and - 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.

[0133] Figures 4 and 5 represent a third embodiment which is a variant of the second embodiment.

[0134] According to this third embodiment, the switching device 5 of each digital probe 6-1, 6-N includes a multiplexer 6b'.

[0135] 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.

[0136] For example, the 6b' multiplexer may be from the Texas Instruments® brand and reference TCA9548APWR.

[0137] 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.

[0138] We observe that the use of a 6-bit multiplexer reduces 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 consider the whole system),

[0139] Reference is now made to Figure 7, which schematically illustrates a digital probe according to a fourth embodiment of this document.

[0140] 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).

[0141] A 6a-1 digital sensor is arranged at the end 8c of the head 8b.

[0142] The response time is proportional to the thickness of the printed circuit board through which the electrical signal travels (i.e., the head 8b and the base 8a). In operation, the reduced thickness of the head 8b therefore allows for a better response time.

[0143] 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.

[0144] Connector 7 provides power to the printed circuit board 8 and transmits the electrical signal.

[0145] Reference is now made to Figure 8, which schematically illustrates a digital probe according to a fifth embodiment of this document.

[0146] 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.

[0147] The 6a-5 digital sensor is arranged at the 8c end of the 8b head.

[0148] In operation, the five digital sensors 6a-1, 6a-2, 6a-3, 6a-4, 6a-5 allow temperature measurements along the head 8b, and establish, for example, an average over the length of the head 8b or a temperature gradient.

[0149] Reference is now made to Figure 9, which schematically illustrates a digital probe according to a sixth embodiment of this document.

[0150] 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 one longitudinal end.

[0151] The printed circuit board head 8b extends longitudinally through the opening 9 and opens onto the outside of the protective housing 6e.

[0152] 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.

[0153] 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.

[0154] Reference is now made to Figure 10, which is a diagram of the temperature error (i.e., the uncertainty) as a function of the temperature measured by the digital measurement system.

[0155] The diagram is taken from a technical document for a Texas Instruments® brand digital temperature sensor, reference TMP1 17.

[0156] The positive temperature error is represented by curve C1 and the negative temperature error is represented by curve C2.

[0157] We observe that the maximum error over the measured temperature range between -20°C and 50°C is ± 0.1 °C.

[0158] The maximum error over the measured temperature range between -40°C and 70°C is ± 0.15 °C.

[0159] The maximum error over the measured temperature range between -40°C and 100°C is ± 0.2 °C.

[0160] The maximum error over the measured temperature range between -55°C and 125°C (up to 150°C) is ± 0.25°C.

[0161] These errors (or uncertainties) are satisfactory for temperature measurements in a test environment such as an aircraft engine test bench that typically operates within the temperature ranges represented.

[0162] It is important to understand 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.

[0163] Taking this consideration into account, we observe that uncertainties are reduced compared to conventional solutions of the prior art.

[0164] 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).

[0165] Digital signals do not suffer from degradation over time or through the different stages of transmission.

[0166] 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.

[0167] 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 the components and the acquisition system. Therefore, the transmitted information remains accurate and faithful to the original value measured by the digital sensor (a sequence of 0s and 1s).

[0168] The digital nature of the digital sensor (particularly in the case of MEMS sensors) therefore allows for more precise and reliable data transmission right 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), which printed circuit board (8) comprises: — 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 with 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. 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 CANI2C layer 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. Digital measuring system (2) according to the preceding claim, wherein the head (8b) extends projecting through the end opening (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) projecting outside the protective housing (6e).

10. Digital measuring system (2) according to any one of the preceding claims, wherein the base (8a) has a first thickness (e1) and the head (8b) has a second thickness (e2) reduced in relation to the first thickness, the head (8b) being flexible.