FR3138519A1 - SYSTEM AND METHOD FOR POSITIONING A MEASURING PROBE IN AN AIR CONDUIT - Google Patents

Abstract

SYSTEM AND METHOD FOR POSITIONING A MEASURING PROBE IN AN AIR CONDUIT The invention mainly relates to a reproducible positioning system (1) of a measuring probe (2) in an aeraulic conduit (3), which probe (2 ) comprises a longitudinal body (4) and a measuring head (5), which reproducible positioning system (1) comprises: • means for inserting and holding (6) the probe (2) comprising a fixing plate (7) intended to be secured to a wall of the pipe (3) and in which is provided a through orifice for receiving the probe body (4), and blocking means (8) of the probe body (2) according to an angle determined relative to the main plane of the plate (7), • means for determining without contact the depth of insertion (9, 10) of the measuring head (5) of the probe (2) in the pipe aeraulic (3), and • means for determining the angular position (9, 11) of the measuring head (5) of the probe (2) in the pipe (3). Figure to be published with the abstract: Figure 1

Description

SYSTEM AND METHOD FOR POSITIONING A MEASURING PROBE IN AN AIR CONDUIT

The invention relates to the field of metrology, and more particularly to a system for reproducible positioning of a measuring probe in an aeraulic type pipe.

The efficiency of a heating or air conditioning system is directly dependent on the flow rate and temperature of the air circulating in the air ducts. Also, hot wire or Pitot type measuring probes are used to measure these parameters of the air circulating in an air duct.

In known manner, the probes are inserted manually into through orifices made in the wall of the sheath, an orifice which can be reversibly blocked. The operator then takes measurements at different depths in the pipe using graduated marks on the body of the probe.

However, this solution is user dependent, so that the depth and angle of insertion of the probe into the aeraulic pipe cannot be determined in an optimal and reproducible manner.

To overcome the various drawbacks mentioned above, the subject of the invention is a system for reproducible positioning of a measuring probe in an aeraulic type pipe.

• Des moyens d’insertion et de maintien de la sonde comportant une platine de fixation prévue pour être solidarisée à une paroi de la conduite et dans laquelle est ménagé un orifice traversant de réception du corps de sonde, et des moyens de blocage du corps de sonde selon un angle déterminé par rapport sur le plan principal de la platine,
• Des moyens de détermination sans contact de la profondeur d’insertion de la tête de mesure de la sonde dans la conduite aéraulique, et
• Des moyens de détermination de la position angulaire de la tête de mesure de la sonde dans la conduite.

To this end, the invention aims at a system for reproducible positioning of a measuring probe in an air duct, which probe comprises a longitudinal body and a measuring head, which reproducible positioning system comprises:

• Means for inserting and holding the probe comprising a fixing plate designed to be secured to a wall of the pipe and in which a through hole is provided for receiving the probe body, and means for blocking the probe body at an angle determined in relation to the main plane of the plate,
• Means for non-contact determination of the depth of insertion of the measuring head of the probe into the air duct, and
• Means for determining the angular position of the measuring head of the probe in the pipe.

• Les moyens de blocage sont reliés de manière amovible à la platine.
• Le système comprend un dispositif de mesure prévu pour être solidarisé au corps de sonde, lequel dispositif de mesure comporte un télémètre laser formant les moyens de détermination sans contact de la profondeur d’insertion de la tête de mesure et une centrale inertielle formant les moyens de détermination de la position angulaire de ladite tête de mesure.
• Le dispositif de mesure comprend un repère de positionnement prévu pour coopérer avec un repère de placement ménagé sur le corps de sonde de mesure.
• Les moyens de blocage sont formés d’un dispositif de blocage du corps de sonde comportant une pièce de maintien dans laquelle est ménagée une encoche en V, un coulisseau apte à coulisser en translation dans l’encoche en V entre une position de libération du corps de sonde et une position de blocage et de maintien du corps de sonde dans l’encoche en V, et des moyens de serrage du corps de sonde entre le fond de l’encoche et le coulisseau.
• Les moyens d’insertion et de maintien comprennent des moyens de liaison du dispositif de blocage à la platine, lesquels moyens de liaison comprennent des encoches ménagées dans la platine de fixation et des pattes solidaires du dispositif de blocage aptes à coopérer avec lesdites encoches.
• Le dispositif de blocage comprend une surface réfléchissante en vis-à-vis du dispositif de mesure lorsque le corps de sonde est bloqué et maintenu dans ledit dispositif de blocage.
• La platine de fixation comprend une face concave prévue pour être solidarisée à la conduite aéraulique et une face opposée plane.
• La platine de fixation comprend un clapet mobile entre une position d’ouverture de l’orifice traversant et une position de fermeture dudit orifice, lequel clapet comprend des moyens de rappel vers sa position de fermeture.
• Le clapet comprend un matériau étanche ménagé sur au moins une partie d’une face dudit clapet en vis-à-vis de la face plane de la platine de fixation lorsque le clapet et en position de fermeture de l’orifice traversant.

The system may also include the following optional features considered separately or in any possible technical combination:

• The locking means are removably connected to the plate.
• The system comprises a measuring device designed to be secured to the probe body, which measuring device comprises a laser range finder forming the means for determining without contact the depth of insertion of the measuring head and an inertial unit forming the means for determination of the angular position of said measuring head.
• The measuring device comprises a positioning mark designed to cooperate with a placement mark provided on the measuring probe body.
• The blocking means are formed of a device for blocking the probe body comprising a holding part in which a V-shaped notch is provided, a slide capable of sliding in translation in the V-shaped notch between a release position of the body probe and a position for blocking and holding the probe body in the V-shaped notch, and means for clamping the probe body between the bottom of the notch and the slide.
• The insertion and holding means comprise means for connecting the blocking device to the plate, which connection means comprise notches provided in the fixing plate and tabs secured to the blocking device capable of cooperating with said notches.
• The blocking device comprises a reflective surface facing the measuring device when the probe body is blocked and held in said blocking device.
• The fixing plate comprises a concave face designed to be secured to the air duct and a flat opposite face.
• The fixing plate comprises a movable valve between an opening position of the through orifice and a closing position of said orifice, which valve comprises return means towards its closed position.
• The valve comprises a waterproof material provided on at least part of one face of said valve facing the flat face of the fixing plate when the valve is in the closed position of the through orifice.

• Déplacement du clapet vers sa position d’ouverture de l’orifice traversant et solidarisation du dispositif de blocage à la platine de fixation ;
• Insertion de la tête de mesure dans la conduite aéraulique au travers de l’encoche en V du dispositif de blocage, de l’orifice traversant de la platine de fixation et du perçage de la conduite ;
• Fixation du dispositif de mesure sur le corps de la sonde de mesure ;
• Mise en appui de contact de la tête de mesure de la sonde contre la paroi de la conduite et calibrage du dispositif de mesure ;
• Réglage de la profondeur d’insertion et de la position angulaire de la tête de mesure selon des paramètres déterminés, et
• Blocage de la sonde via les moyens de serrage.

The invention also relates to a method for reproducible positioning of a measuring probe through a through hole made in a wall of an air duct with a reproducible positioning system as described previously, the fixing plate of said system being secured to the pipe and its through orifice being opposite the bore passing through the wall of said pipe, which probe comprises a longitudinal body and a measuring head, which method comprises the steps of:

• Movement of the valve towards its opening position of the through hole and securing of the blocking device to the fixing plate;
• Insertion of the measuring head into the aeraulic pipe through the V-shaped notch of the blocking device, the through hole of the fixing plate and the bore of the pipe;
• Fixing the measuring device on the body of the measuring probe;
• Contact support of the measuring head of the probe against the wall of the pipe and calibration of the measuring device;
• Adjustment of the insertion depth and the angular position of the measuring head according to determined parameters, and
• Blocking of the probe via the clamping means.

• L’étape de fixation du dispositif de mesure est réalisée en faisant coïncider le repère de positionnement dudit dispositif de mesure et le repère de placement de la sonde.

The process may also include the following optional characteristics considered in isolation or in all possible technical combinations:

• The step of fixing the measuring device is carried out by making the positioning mark of said measuring device and the placement mark of the probe coincide.

Other characteristics and advantages of the invention will emerge clearly from the description given below, for information only and in no way limiting, with reference to the appended figures:

There represents a perspective view of the positioning system in use in an aeraulic pipe;

There shows a perspective view of the measuring device installed on the body of the measuring probe;

There represents part of the means for fixing the measuring device to the probe body;

There represents a perspective view of the means of insertion and maintenance;

There represents a front view of the fixing plate installed on the pipe, the valve being in the closed position;

There represents a front view of the plate of the , the valve being in its open position;

There represents a view of the blocking device installed on the fixing plate of Figures 5 and 6;

There represents a side view of the valve according to an alternative embodiment pivotally mounted on the plate of the insertion and holding means;

There represents a perspective view of part of the blocking device of the .

It is firstly specified that in the figures, the same references designate the same elements whatever the figure in which they appear and whatever the form of representation of these elements. Likewise, if elements are not specifically referenced in one of the figures, their references can easily be found by referring to another figure.

It is also specified that the figures essentially represent an embodiment of the object of the invention but that there may be other embodiments which meet the definition of the invention.

The invention finds its application in the field of metrology, and in particular in measuring the flow rates and temperature of the air circulating in air ducts, for example forming part of air heating and/or air conditioning systems. .

These aeraulic pipes 3 – which we will simply call pipes 3 in the remainder of the description – generally have a circular or parallelepiped shape in cross section. The air flow which flows inside these pipes 3 is laminar, that is to say that the air flows almost in a straight line in the pipe 3. In addition, the greater the flow The air is further from the wall of pipe 3, the greater its speed, whereas the speed of the air flow is almost zero in contact with the wall of pipe 3.

In other words, the speed of the air flow flowing in pipe 3 is not uniform at every point of the pipe, but has a parabolic profile. In addition, the flow flows along the longitudinal axis of pipe 3.

Thus, to obtain a reproducible measurement of the flow speed at any point in pipe 3, it is necessary to position a measuring probe 2 of the Pitot probe or hot wire probe type at a depth that can be determined in a reproducible manner in pipe 3. .

In reference to the , these measuring probes 2 comprise a probe body 4 and a measuring head 5 provided at the free end of the probe 2. The Pitot probe is bent at 90° while the hot wire probe (not shown) is rectilinear and its measuring head includes a window for measuring air flow.

The particularity of these measuring heads 5, both for the Pitot probe and the hot wire probe, is that the air flow measurement depends on the angular position of the measuring head 5 relative to the direction of the flow: the The most reliable measurement is obtained when the measuring head is oriented in the direction of flow. In other words, the window of the hot wire probe must extend perpendicular to the air flow while the measuring portion 25 of the Pitot probe extending between the measuring head 5 and the elbow must extend parallel to the longitudinal axis of the pipe 3.

• Déterminer de manière reproductible la profondeur d’enfoncement de la tête de mesure 5 dans la conduite 3 ;
• Déterminer de manière reproductible la position angulaire de la tête de mesure 5 vis-à-vis du sens du flux d’air (c’est-à-dire vis-à-vis de l’axe longitudinal de la conduite 3), et
• Assurer une position de maintien et de blocage reproductible de la sonde 2 durant la mesure, et en particulier un positionnement angulaire reproductible entre l’axe longitudinal de la conduite 3 et l’axe longitudinal du corps de sonde 4.

A reproducible measurement of the air flow in pipe 3 therefore depends on the ability to position the probe 2 in a reproducible manner in the pipe, that is to say:

• Determine in a reproducible manner the depth of insertion of the measuring head 5 into pipe 3;
• Reproducibly determine the angular position of the measuring head 5 with respect to the direction of the air flow (i.e. with respect to the longitudinal axis of the pipe 3), and
• Ensure a reproducible holding and blocking position of the probe 2 during the measurement, and in particular a reproducible angular positioning between the longitudinal axis of the pipe 3 and the longitudinal axis of the probe body 4.

In reference to the , the invention proposes a reproducible positioning system 1 of the measuring probe 2 which comprises means for inserting and maintaining the probe 6 in the pipe 3, means for determining without contact the depth of insertion of the measuring head 10 and means for determining the angular position of the measuring head 11 in the pipe 3 – in particular the angle formed between the longitudinal axis of the pipe 3 and the axis of the measuring portion of the probe 2 if it is a Pitot probe.

According to the invention, the means for determining without contact the insertion depth of the measuring head 10 and the means for determining the angular position of said measuring head 11 are brought together within the same device called a measuring device. measure 9 in the rest of the description.

This device 9 includes a box and a man-machine interface to allow the user to use the device 9, and in particular to determine the desired measurement parameters.

With reference to Figures 2 and 3, the measuring device 9 comprises fixing means 26 to the probe body 4, which fixing means 26 advantageously comprise two parts 27 pivotally connected by a hinge 30, each of the parts comprising a groove 28 to allow the housing of the probe body 4. The fixing means 26 also comprise a cylindrical sleeve 50 made of a deformable material, for example rubber, which is intended to be installed in the grooves 28 and around the probe 2 This sleeve 50 ensures the compatibility of the fixing means 26 with different diameters of probe bodies 4. Finally, the fixing means 26 comprise a tightening means 29 making it possible to bring the two grooved parts 27 together or, on the contrary, to move them apart, this tightening means 29 being for example a captive screw equipped with a handle button. In addition, the sleeve 50 prevents any rotational sliding between the probe body and the parts 27 of the fixing means 26.

In addition, the fixing means 26 comprise a positioning mark which is intended to coincide with a positioning mark provided on the probe body 4. In other words and following the installation of the measuring device 9 on the body probe 4, the coincidence between the two marks allows the operator to ensure that the measuring device 9 is always placed in the same place on the probe body 4. Alternatively, the probe body 5 comprises a single indicator of the orientation of the measuring head 5 in pipe 3. This is for example a rod secured to the probe body 4 and oriented parallel to the measuring portion 25 of the Pitot probe or even a key indicating the orientation of the measuring head 5 of the hot wire probe.

Advantageously, the measuring device 9 comprises a laser rangefinder 10 forming the means for determining without contact the insertion depth of the measuring head 5, and an inertial unit 11 forming the means for determining the angular position of the measuring head. measurement 5 of probe 2.

The means for inserting and maintaining the probe in line 6 will now be described with reference to Figures 4 to 9.

The insertion and holding means 6 comprise a fixing plate 7 to the pipe 3. In a non-limiting manner, this plate 7 is of rectangular shape and comprises two opposite longitudinal edges 31 and two opposite transverse edges 32. Furthermore, the fixing plate 7 comprises an external flat face and an internal opposite face intended to be arranged in contact support against the wall of the pipe 3. Advantageously, this internal face is flat if the pipe 3 has a quadrilateral shape in cross section, and this internal face is curved if the pipe 3 has a circular shape in cross section. In this way, the internal face of the plate 7 matches the shape of the pipe 3 and the entire internal face comes to rest against the wall of the pipe 3.

In a particularly advantageous manner, the plate 7 comprises two plates in contact support: a flat external plate comprising the external face and an internal plate comprising the internal face which matches the shape of the pipe 3. The internal plate, for example made of plastic, can therefore be changed depending on the shape of the pipe 3, while the external plate is identical for all types of pipes. The two external and internal plates are secured together, for example using screws.

The fixing plate 7, which for example is screwed into the wall of the pipe 3, comprises a through orifice 13 which is opposite a drilling 12 made in the wall of the pipe 3. Furthermore, the plate 7 comprises a valve 22 pivotally mounted on a hinge 33 between a closing position of the through orifice 13 and an opening position of said orifice 13.

According to a first alternative shown in Figures 4 to 7, the valve 22 comprises return means 23 towards its closed position, for example a torsion spring.

According to a second alternative represented in , the valve 22a does not include return means, but means 51 for maintaining the valve in its closed position. These holding means 51 are for example a permanent magnet (as shown in ), in which case the plate 7 or at least its external plate is made of a magnetic metal such as galvanized steel, or else a captive screw intended to cooperate with a threaded orifice made in the plate 7. In addition, the valve 22a comprises a handle 52, which if necessary is integral with the head of the captive screw when the latter forms the holding means 51. This handle 52 can also be present on the valve 22 shown in Figures 4 to 7.

Furthermore, at least part of the internal face of the valve 22, that is to say the face of the valve facing the external face of the fixing plate 7 when said valve 22 is in its closed position , is covered with a waterproof material 24. For example, the material is an annular seal 24 made of rubber or EPDM foam (for “ethylene-propylene-diene monomer”) which makes it possible to make the hole 12 in the pipe 3 waterproof when the valve 22 is in its closed position.

Finally, the plate 7 comprises two notches 19 provided in the vicinity of the two opposite transverse edges 32 of said plate 7, at the level of its external flat face.

The means for inserting and holding the probe 6 further comprise means 8 for blocking the probe body 4 at an angle determined relative to the main plane of the fixing plate 7.

The blocking means are formed of a blocking device 8 comprising a holding part 14 in which a V-shaped notch 15 is provided, a slide 16 capable of sliding in translation in the V-shaped notch 15 between a release position of the probe body 4 and a position for blocking and holding the probe body 4 in the V-shaped notch 15, and means for clamping the probe body 17 between the slide 16 and the bottom of the notch 18.

The holding part 14 has the general shape of a straight rectangular block, the dimensions of which are slightly smaller than that of the fixing plate 7, which holding part 14 comprises two opposite faces, respectively internal and external 34, two transverse lateral faces opposite 35 and two opposite longitudinal side faces 36.

The V-shaped notch 15 is formed in the wall of the holding part 14 from one of the longitudinal side faces 36. More precisely, this notch 15 comprises a first rectilinear part which extends from the longitudinal side face considered 36 and a second trapezoid-shaped part which narrows towards the bottom of the notch 18. Furthermore, the bottom of the notch 18 has a curvature equal to the curvature of the probe body 4.

The slide 16 of the blocking device 8 is also in the shape of a trapezoid, complementary to the shape of the second part of the V-shaped notch 15 of the holding part 14. The slide 16 comprises an upper face 37, a lower face 38 intended to be opposite the bottom of the notch 18 of the holding piece 14, and two side faces 39 extending in two intersecting planes. Furthermore, the slide 16 comprises a threaded through hole 40 formed in the wall from its upper face 37. Finally, to allow the correct positioning of the slide 16 in the notch 15, said slide 16 comprises two grooves 41 provided at the level of two opposite edges of the slide 16, each edge making the junction between the upper face 37 and the side face considered 39 of the slide 16. These grooves 41 cooperate with two tenons 42 provided on the two side faces facing the rectilinear portion of the V-shaped notch 15 of the holding part 14.

Furthermore, the blocking device 8 comprises a bracket 43 secured to the holding part 14, a main leg 44 of which bears against the internal face 34 or the external face of the holding part 14 and a secondary leg 45 of which comes resting against the upper side face of said holding piece 14.

The main leg 44 comprises a bore 46 which faces the notch 15 of the holding part 14, the through hole 13 of the fixing plate 7 and the bore of the pipe 12, while the secondary leg 45 comprises a through orifice 47 which faces the threaded orifice 40 of the slide 16.

The clamping means 17 comprise a screw 48 passing through the tapped orifice 40 and the orifice 47 of the aforementioned secondary leg, which screw comprises a handle 49 provided at its free end. Thus, the actuation of the screw 48 in one direction or the other will cause the slide 16 to move closer or further away from the bottom of the notch 18 of the holding part 14.

The bracket 43 further comprises two tabs 20 provided on two opposite transverse side edges of the main leg 44 and are designed to cooperate with the notches 19 provided in the fixing plate 7. Thus, the blocking device 8 is connected so removable to the fixing plate 7. Furthermore, once fixed to the plate 7 and when the valve 22 is in the open position, the drilling 12 of the pipe 3, the through hole 13 of the plate 7, the The notch 15 of the holding part 14 and the drilling of the bracket 46 are opposite each other to allow the insertion of the probe body 4 into the drilling 12 of the pipe 3. In addition, once installed against the plate 7, the internal face 34 of the holding part 14 is opposite the external face of the plate 7.

Finally, the holding part 14 comprises, at its external face opposite the internal face 34, a reflective surface 21 which improves the reflection of the measuring ray coming from the telemeter 10. Thus, the contactless measurement of distance via this telemeter laser 10 is optimized.

A method for reproducibly positioning a measuring probe 2 using the reproducible positioning system 1 of the invention will now be described.

During the first step, the operator wishing to carry out measurements of flow rate and, where applicable, temperature of the air circulating in line 3 moves the valve 22 of the fixing plate 7 towards its open position, then inserts the tabs 20 of the blocking device 8 in the notches 19 made in the fixing plate 7.

During the second step, the operator inserts the measuring head 5 into the pipe 3 through the V-shaped notch 15 of the blocking device 5, the through hole 13 of the plate 7 and the bore 12 of said conduct 3.

During the third step, the operator fixes the measuring device 9 on the probe body 4, making the positioning mark of said device 9 coincide with the placement mark on the probe body 4.

Advantageously, the fixing of the measuring device 9 can be carried out before the insertion of the measuring head 5 into the pipe 3, or even before the fixing of the blocking device 8 to the plate 7.

Alternatively during the third step, when the measuring device does not have a positioning mark, then the operator orients the measuring head 5 in the direction of the air flow using the rod or the key made on the probe body 4. Furthermore, the operator can refine the positioning of the measuring head 5 in the direction of the flow by following the air flow measurement in real time: the air flow being constant, the higher the value of the flow measurement is higher, the more the measuring head 5 is oriented parallel to the direction of the air flow. Once the optimal measurement has been obtained, the operator blocks the position of the probe 2 via the blocking means 6 then installs the measuring device 9 on the probe body 4

During the fourth step, the operator turns on the measuring device 9 and moves the measuring probe 2 to a stop depth, that is to say the head of the probe 5 comes into contact support against the wall of the pipe 3. The operator then calibrates the measuring device 9 by carrying out a tare via the control means of the measuring device 9, so that the distance measurement returns the value 0 when the measuring head 5 of probe 2 is in the stop position.

During the fifth step, the operator moves the measuring probe 2 to the desired depth: the measuring device 9 returns the distance measurement separating the telemeter 10 from the reflective surface 21 secured to the holding piece 14, adjusted by the previously determined tare.

During this same step, the operator defines the orientation of the probe 2 around the longitudinal axis of the probe body 4 in the pipe 3 using the inertial unit 11. Advantageously, the inertial unit 11 indicates an angle d zero inclination when the measuring portion 25 of the probe 2 is oriented in the direction of the air flow, for optimal measurement of the flow rate.

During the sixth and final step, the operator activates the clamping means 17 to block the probe 2 in the blocking device 8. Advantageously, the longitudinal axis of the probe body 4 is always oriented at the same angle relative to to the plane of plate 7, typically 90°.

The means for inserting and holding 6 of the probe 2, the means for determining without contact the insertion depth 9, 10 of the measuring head 5 of the probe 2 and the means for determining the angular position 9, 11 of the measuring head 5 in the pipe 3 therefore interact synergistically, the insertion and holding means 6 making it possible to block the probe 2 in the pipe at a determined reproducible angle between the longitudinal axis of the probe body and the plane of the plate, while the means for determining without contact the insertion depth 9, 10 and the means for determining the angular position 9, 11 respectively make it possible to measure precisely and reproducibly the depth of insertion into the pipe 3 of the measuring head 5 and the orientation of the latter relative to the direction of flow of the air flow in the pipe 3.

The system of the invention 1 allows the carrying out of precise measurements of the air flow rate at different points of the pipe 3 is therefore facilitated, which allows an operator to obtain a precise representation of the air flow in pipe 3, and to identify, for example, defects which would tend to make the flow turbulent at certain points in the internal space of pipe 3. In particular, the reproducibility of the placement of the probe is based on measurements of angular and distance orientation, which makes it possible to overcome the variability inherent to the operator.

Claims (10)

Reproducible positioning system (1) of a measuring probe (2) in an air duct (3), which probe (2) comprises a longitudinal body (4) and a measuring head (5), which reproducible positioning system (1) includes:

• Means for inserting and holding (6) the probe (2) comprising a fixing plate (7) designed to be secured to a wall of the pipe (3) and in which a through orifice (13) of receiving the probe body (4), and the blocking means (8) of the probe body (2) at a determined angle relative to the main plane of the plate (7),
• Means for determining without contact the depth of insertion (9, 10) of the measuring head (5) of the probe (2) in the aeraulic conduit (3), and
• Means for determining the angular position (9, 11) of the measuring head (5) of the probe (2) in the pipe (3).

System (1) according to the preceding claim, characterized in that the locking means (8) are removably connected to the plate (7). System (1) according to claim 1 or 2, characterized in that it comprises a measuring device (9) designed to be secured to the probe body (4), which measuring device (9) comprises a laser rangefinder forming the means for determining without contact the insertion depth (10) of the measuring head (5) and an inertial unit forming the means for determining the angular position (11) of said measuring head (5). System according to any one of the preceding claims, characterized in that the blocking means (8) are formed of a device for blocking the probe body (4) comprising a holding part (14) in which a notch is formed in V (15), a slide (16) capable of sliding in translation in the V-shaped notch (15) between a position for releasing the probe body (4) and a position for blocking and holding the probe body ( 4) in the V-shaped notch (15), and clamping means (17) of the probe body (4) between the bottom of the notch (18) and the slide (16). System according to any one of the preceding claims, characterized in that the insertion and holding means (6) comprise means for connecting the blocking device (8) to the plate (7), which connection means comprise notches (19) made in the fixing plate (7) and tabs (20) secured to the blocking device (8) capable of cooperating with said notches (19). System according to claim 4 or 5, characterized in that the blocking device (8) comprises a reflecting surface (21) facing the measuring device (9) when the probe body (5) is blocked and held in said blocking device (8). System according to any one of the preceding claims, characterized in that the fixing plate (7) comprises a concave face intended to be secured to the aeraulic pipe (3) and a flat opposite face. System according to any one of the preceding claims, characterized in that the fixing plate (7) comprises a movable valve (22) between an opening position of the through orifice (13) and a closing position of said orifice ( 13). System according to the preceding claim, characterized in that the valve (22) comprises a waterproof material (24) provided on at least part of one face of said valve (22) facing the flat face of the plate fixing (7) when the valve (22) is in the closed position of the through hole (13). Method for reproducibly positioning a measuring probe (2) through a through bore (12) made in a wall of an air duct (3) with a reproducible positioning system (1) according to claim 9 or 10 , the fixing plate of said system (1) being secured to the pipe (3) and its through orifice (13) being opposite the bore (12) passing through the wall of said pipe (3), which probe ( 2) comprises a longitudinal body (4) and a measuring head (5), which method comprises the steps of:

• Movement of the valve (22) towards its opening position of the through hole (13) and securing of the blocking device (8) to the fixing plate (7);
• Insertion of the measuring head (5) into the aeraulic pipe (3) through the V-shaped notch (15) of the blocking device (8), the through hole (13) of the fixing plate (7 ) and the drilling (12) of the pipe (3);
• Fixing the measuring device (9) to the body of the measuring probe (4);
• Contact support of the measuring head (5) of the probe against the wall of the pipe (3) and calibration of the measuring device (9);
• Adjustment of the insertion depth and the angular position of the measuring head (5) according to determined parameters, and
• Blocking the probe (2) via the clamping means (17).