ITMI20121890A1 - MEASUREMENT DEVICE FOR PARAMETERS, SUCH AS HUMIDITY OR DENSITY, OF A POWDER OR GRANULAR MATERIAL - Google Patents

Description

DESCRIPTION

â € œ DEVICE FOR MEASURING PARAMETERS, SUCH AS HUMIDITY OR DENSITY, OF A POWDER OR GRANULES MATERIALâ €

The present invention relates to a device for measuring parameters, such as humidity, of a powdered or granular material.

In particular, the device in accordance with the invention is capable of taking samples of powdered material from a continuous flow of the same to detect its moisture content.

The device can be used to analyze products in powder or granules, for example of a food, pharmaceutical or other nature, by means of non-continuous measurements of the parameter of interest (i.e. measurements carried out at different times on samples of material taken and then returned to the flow main material).

Furthermore, the same can be advantageously used in drying, granulation, agglomeration, instantization, coating, stratification or spheronization plants, particularly of the fluidized bed type, or more.

There are known and currently marketed devices for measuring the humidity of powdered materials that exploit the use of microwave sensors to detect the chemical-physical properties of interest by operating directly on the material that moves in a continuous flow in the processing phases of the latter; such devices allow, for example, the collection of a sample of the material directly from the flow and an analysis of the same,

Among the known devices, the patent WO 2010/125454 describes a system capable of withdrawing a predetermined quantity of the same from a continuous flow of powdered material, conveying it into a cylindrical-shaped measuring chamber outside of which it is positioned the microwave sensor. Once the measurement has been carried out, an appropriate discharge channel allows the outflow of the collected material with movement, through a suitable auger, of the analyzed material which is re-introduced into the main flow. In an alternative embodiment described in the same document, the material to be sampled is taken by means of a to and fro movable actuator (for example a piston) sliding inside a measuring cavity equipped with an access / exit for the coincident material .

In particular, a piston equipped with a scraper head moves inside the aforementioned measuring cavity to allow the material to enter and to detect its properties, as well as causing it to come out once the measurement is finished.

From the structural point of view, the measurement chamber is delimited by internal cylindrical walls and the microwave sensor is positioned externally to an intermediate zone of the chamber itself.

In detail, an internal surface of the sensor cooperates with the cylindrical walls of the chamber to define the measurement volume and is in direct contact with the material to be measured.

The type of measurement devices, briefly mentioned above, while providing humidity measurements with good approximation, nevertheless appear to be improved from the point of view of construction simplicity (first type of measurement device) and from the point of view of accuracy and repeatability of the measurement ( second form made va).

It is also known from the American document US 2010/0288040 a sampling device configured to take a predetermined quantity of powder material from a continuous flow of the same to bring it, by means of a translation of a slide, inside a measuring device .

The aforementioned patent only illustrates the mechanical movement structure of the slide, without providing any details of the measurement systems and their operation.

The possibility of using different sensors is mentioned, including load cells, cameras or microwave sensors.

In this situation, a main purpose of the embodiments described below is to improve the devices for measuring the properties of a powdered or granular material.

A further object is to provide a humidity measuring device (which can be used to sample a flowing material on-line) which is endowed with good measuring accuracy and guarantees excellent repeatability of the measures themselves.

An auxiliary objective is also to improve the seal against the ingress of dust and unwanted material inside the measurement area. It is also an auxiliary purpose that of providing a calibration procedure, possibly configurable, which allows a considerable improvement in the performance of the device allowing a measurement accuracy that is difficult to reach without costly design choices.

This and still other objects are substantially achieved by a device for measuring parameters, such as density or humidity, of a powdered or granular material coming from a continuous flow of the material itself, in accordance with one or more of the annexed claims.

In an independent aspect a device for measuring parameters, such as density or humidity, of a powdered material or granules in a continuous flow of said material is provided, the measuring device comprising: a fixed support frame (2) which can be associated with a structure suitable for receiving a flow of powdered or granular material, said fixed frame (2) having a sliding seat (6) having an inlet (7), the sliding seat being delimited by at least one containment structure (8) ; at least one slide (3) movable, relative to the fixed support frame (2), in the sliding seat (6) between a first position at least partially extracted with respect to the frame (2) and with respect to the sliding seat (6) and a position at least partially retracted with respect to the frame (2) towards the inside of the sliding seat (6), said slide (3) comprising at least one collection cavity (4) which, in the first extracted position of the slide (3), is at least partially at the end of the continuous flow to receive material in powder or granules and, in the retracted position of the slide (3), allows the measurement of parameters, and is contained in the sliding seat (6) of the fixed support frame (2); at least one microwave sensor (5) for detecting a signal indicative of a value of said parameters, said sensor (5) being constrained to the fixed frame (2) in correspondence with the containment structure (8), the sensor (5) presenting a substantially flat head (5 a) and the containment structure (8) presenting a base wall (9) equipped with a flat portion (9a) of constant thickness, the flat head (5a) of the microwave sensor (5) being arranged parallel, and in particular in contact, with the flat portion (9a) of the base wall (9) and being placed externally to the sliding seat, in the retracted position of the slide (3) the collection cavity (4) being positioned on the side opposite the head (5a) of the microwave sensor (5) with respect to the base wall (9).

In a further independent aspect, a device for measuring parameters, such as density or humidity, of a powdered material or granules in a continuous flow of said material is provided, the measuring device comprising: a fixed support frame (2) which can be associated to a structure adapted to receive a flow of powdered or granular material, said fixed frame (2) having a sliding seat (6) having an inlet (7), the sliding seat being delimited by at least one containment structure (8 ); at least one slide (3) movable, relative to the fixed support frame (2), in the sliding seat (6) between a first position at least partially extracted with respect to the frame (2) and with respect to the sliding seat (6) and a position at least partially retracted with respect to the frame (2) towards the inside of the sliding seat (6), said slide (3) comprising at least one collection cavity (4) which, in the first extracted position of the slide (3), is at least partially inside the continuous flow to receive material in powder or granules and, in the retracted position of the slide (3), allows the measurement of parameters, and is contained in the sliding seat (6) of the fixed support frame (2) ; at least one microwave sensor (5) for detecting a signal indicative of a value of said parameters, said sensor (5) being constrained to the fixed frame (2) in correspondence with the containment structure (8); and a control unit (22) configured to receive the signal indicative of the value of said parameter and determine a reading of the same parameter, the control unit (22) being programmed to carry out a calibration phase to obtain a measurement accurate, in said calibration phase the control unit (22) being programmed to receive a plurality of parameter value measurements taken, by means of the microwave sensor (5), on different samples of the same powder or granule material of which the real value of the parameter is known, for example by laboratory analysis, the control unit (22) being programmed to carry out the calibration phase by means of a linear combination, suitably weighted, between a multiple linear regression of the values measured values and a Support Vector Regression of the measured values to minimize a difference in the reading of the device compared to the real value of the parameter. Further characteristics and advantages will become clearer from the detailed description of the measuring device, as illustrated in the following figures, provided for illustrative purposes only, and therefore not for limiting purposes, in which:

Figure 1 shows a perspective view of the measuring device coupled to a section of the channel of an apparatus for the continuous processing of powdered material;

Figures 2, 3 and 4 show the measuring device, respectively, in a first and second position for extracting a slide with respect to a fixed frame and in a retracted position of the slide inside the fixed frame;

Figure 5 shows a longitudinal section of the measuring device;

Figure 6 shows a detail of the section of Figure 5;

Figure 7 shows an exploded view of the measurement device of Figure 1;

Figure 8 illustrates the device of Figure 4 with some elements removed in such a way as to highlight its internal structure.

With reference to the aforementioned figures, 1 identifies a device for measuring parameters, in particular density or humidity, of a material in powder or granules.

In particular, the measuring device is designed to take a predetermined number of samples of material to be analyzed from a continuous flow of the material itself crossing a channel or duct to which the measuring device is associated.

Observing in particular figure 1, the measuring device is represented in a situation of coupling to a passage duct 100 (only partially represented), which, in use, is crossed by the material in powder or granules during the phases of processing of the material itself.

In particular, the measuring device is designed to operate inside the passage duct to take a predetermined quantity of material in powder or granules, to transfer it to the interior of a measuring area, where the detection takes place (by means of a microwaves) of the value of the desired parameter and then to bring the collected material back into the main flow and release it.

In particular, the configuration illustrated in Figure 1 refers, as it is better clarified below, to a first position of the measuring device in which a movable slide 3 is at least partially extracted with respect to a fixed frame; in this position the device is at least partially inside the continuous flow of material and is able to take a sample of the same. As can also be seen in Figure 1, the flow of material moves along the axis of the passage duct 100 in the direction indicated by the arrow A.

The measuring device 1 is by way of example coupled to the passage duct 100 by means of an adapter 26 configured to mate, on one side, to the external surface of the passage duct and, on the other, to a fixed frame of support 2 of the sensor device.

Moving on to an examination of the structure of the latter and in particular observing figures 7 and 8, it can be seen that the measuring device is first of all equipped with a fixed support frame 2, which, in use, is rigidly constrained to the duct passage 100 crossed by the flow of powder material (fig. 1).

For example, there may be a mounting flange 27 to the duct itself or another similar fastening system.

The fixed frame 2 is in the form of a tubular duct defining, internally, a sliding seat 6 between an inlet 7 and an outlet 28. In detail, the sliding seat 6 is delimited by a containment structure 8 comprising a base wall 9, two side walls 29 emerging from the base wall 9, which are joined together at the top by means of an upper wall 30.

In the embodiment example, referred to in Figures 7 and 8, the sliding seat has a polygonal section, in particular rectangular, and the internal surfaces of the aforementioned base wall 9, side 29 and upper 30 are flat (however it appears it is relevant that at least the base wall 9 has a flat exposed internal surface as better explained below).

In correspondence with the inlet 7, there is a support portion 11 which emerges from the base wall 9 away from the sliding seat 6. This support portion can be made in one piece to the fixed frame 2 or constrained (directly or indirectly) rigidly to the latter.

The base wall 9 and the support portion 11 define a flat upper surface at the same height and substantially free of discontinuities. As can also be seen from figure 7, the sliding seat 6 has a constant cross section and extends along a main axis M of development of the fixed frame.

Observing in particular the sections of figures 5 and 6, it can be seen that the base wall 9 has a portion 9a of reduced thickness with constant section, in particular arranged near the inlet 7.

Returning to observing figures 7 and 8, it can be seen that the measuring device also comprises a slide 3 which is movable, relative to the fixed support frame 2, inside the sliding seat 6 between a first position at least partially extracted with respect to the frame 2 and with respect to the sliding seat 6 (fig.

2), a second position at least partially extracted with respect to the frame 2 and with respect to the sliding seat 6 (fig. 3) and a position at least partially rearward with respect to the same frame and inside the sliding seat 6 (fig. 4) .

In particular, the three configurations mentioned are clearly visible in figure 2 (first position extracted), figure 3 (second position extracted) and figure 4 (position retracted).

The slide 3 has an elongated conformation and extends along a movement axis B (see Figure 7).

It has at least one collection cavity 4 defined by a through hole which extends between an upper inlet 4a and a lower outlet 4b through the entire thickness of the slide 3.

As an example, the conformation of the collection cavity 4 is truncated cone with the area of the upper inlet 4a smaller than the area of the lower outlet 4b (inverted truncated cone),

Obviously, alternative embodiments of the cavity are equally possible, such as for example straight truncated cone, cylindrical shape or truncated pyramid, possibly also inverted.

Observing in particular figure 2, it can be seen how the first extracted position of the slide 3 with respect to the frame 2 arranges the cavity 4 overlapping the support portion 11, in such a way that the upper surface of the latter closes the ™ lower outlet 4b of the cavity.

In particular, in this configuration (which is also the configuration illustrated in figure 1) the powder material that advances along the movement direction A inside the passage duct 100 is intercepted by the slide 3 and the collection cavity 4 is filled with material.

The latter obviously cannot come out of the lower outlet 4b which is intercepted by the support portion 11.

Once a sufficiently long time has been waited to allow the filling of the cavity 4, the slide 3 is moved towards the inside of the sliding seat 6 in such a way that the cavity 4 (which in the first extracted position was outside the sliding seat 6) is moved inside the seat of the fixed frame, bringing the device into the configuration shown in figures 4 and 5.

The configuration of figure 4 is that in which the value of the parameter of interest is measured (for example the humidity of the sample of collected material).

This condition is illustrated in the sections of figures 5 and 6, where it is noted how the collection cavity is brought in correspondence with the flat portion 9a of the base wall 9.

Again as visible in the aforementioned sections, the measuring device also comprises at least one microwave sensor 5 designed to detect a signal indicative of the value of the parameter of interest, for example proportional to the humidity or density of the material.

The sensor 5 is constrained to the fixed frame 2 in correspondence with the containment structure 8 of the latter and in particular has an upper head 5a with a substantially flat upper surface, which is arranged parallel to, and in particular in contact, with respect to to the flat portion 9a of the base wall 9.

The sensor is placed externally to the sliding seat 6, but is constrained in an engagement seat 10 configured to receive and center the head 5a of the sensor 5.

As can also be seen, the engagement seat 10 is arranged externally to the sliding seat 6 and involves a reduction in thickness, at least localized, of the base wall 9.

In other words, the flat portion 9a of constant thickness of the base wall will generally be counter-shaped to the head 5a of the sensor 5 (for example, it will have a circular shape as in the representation of the accompanying figures).

In this way the lower outlet 4b of the collection cavity 4 is in substantial contact with the base wall precisely in correspondence with the flat portion 9a and therefore there are no interstices between the lower outlet 4b and the base wall 9 (do not deceive the thin distances of figure 6 shown only to highlight and distinguish the various components).

The head 5a of the sensor 5 is also in direct contact with the flat portion 9a, thus avoiding the presence of interstices between these latter elements,

How it is possible to understand, therefore, the sensor is precisely positioned with respect to the collection cavity 4 and spaced from it only by the thickness of the flat portion 9a (constant and of reduced dimensions).

The sensor itself is never moved from its relative position during the various measurements and therefore is always substantially correctly arranged with respect to the sample to be analyzed.

In this way, the measurement accuracy is significantly improved as the relative position between the sensor head and the material is precisely controlled.

As can be seen in figures 5 to 8, the microwave sensor 5 is precisely positioned and constrained with respect to the fixed frame also thanks to the presence of mounting flanges 23 which constrain it immovably and keep it in the correct relative position during all operating phases of the measuring device.

As can also be understood by observing figures 5, 7 and 8, the slide 3 is movable inside the sliding seat 6 with a back and forth motion, that is, it can be moved with respect to the fixed body 2.

For this purpose, provision is made for the adoption of a movement mechanism 12 which allows the movement between the aforementioned first and second extracted positions and the retracted position of the slide and vice versa.

Observing figure 7, it can be seen that the movement mechanism 12 comprises at least one motor 13 active on a pulley or driving wheel 15 to move a suitable belt 14, optionally a toothed belt (not shown), which allows to control optimally the relative positions of the slide 3 with respect to the fixed frame 2.

An appropriate rotation of the motor 13 commands a corresponding movement of the belt 14 which, in turn, integrally drives a locking element 31 rigidly engaged to the slide 3.

In this way the displacements of the slide 3 along its own movement axis B coinciding with the axis of the sliding seat M are controlled. 16 suitably housed inside an engagement seat 17 of the same slide 3.

The vibration generator 16 is active on the slide 3 to generate a vibratory motion on the same, at least in the retracted position of the slide 3, as will be better clarified later on.

It should also be noted that the measuring device is also equipped with suitable systems to avoid the entry of unwanted material, in particular into the sliding seat 6.

In this regard, the slide 3 comprises, in correspondence with its own central area, an external gasket 32 capable of preventing the entry of dust or dirt, in particular through the outlet 28 of the sliding seat 6.

In correspondence with inlet 7, on the other hand, there is a scraper 18 active on slide 3, particularly during the entry phase of the latter inside the sliding seat 6.

The scraper 18 has an active scraper portion 18a active at least on the upper surface and on the lower surface of the slide 3.

As can be seen in figure 7, the scraper surface 18a is also active in correspondence with the lateral surfaces of the slide 3 and actually defines a closed profile substantially counter-shaped to a cross section of the slide, the scraper 18 is held in position by a mounting frame 19 engaged to the fixed frame in correspondence with the aforementioned inlet 7.

In this regard, the mounting frame 19 has a through hole 20 configured to allow the slide 3 to pass through.

The scraper 18 is interposed between the mounting frame 19 and the fixed frame and has a respective through hole centered on the previously described hole, preferably slightly smaller than the size of the through hole 20 of the frame 19.

In this way, during the movement of the slide 3, the external surfaces of the latter come into contact with the scraping surface 18a which prevents unwanted material from entering the sliding seat 6.

To avoid the entry of unwanted material from the outside, there is also an additional external gasket 21 received in a suitable front seat of the mounting frame 19.

The measuring device 1 is controlled by means of a control unit 22, for example a microprocessor control unit (fig. 5), which can be integrated into the measuring device itself or connected via an external connection. .

In other words, the single control unit 22 could possibly also belong to a conventional electronic terminal on whose memory the management software of the measuring device is loaded.

In any case, the control unit 22 is configured to receive the signal indicating the value of the parameter of interest and, through the latter, to determine a reading of the same parameter.

Furthermore, the control unit 22 is active on the movement mechanism 12 to command the movement of the slide between the various operating positions and also to determine the activation of the vibration generator 16.

Given the above, described in structural terms, the measuring device in accordance with the embodiment just described operates as follows.

When it is necessary to measure a parameter of interest, for example the humidity of a powder material that is flowing along the passage duct 100, the slide 3 is positioned with respect to the fixed support frame 2 in so as to be in the first extracted position illustrated in figure 1 and in figure 2.

In this condition the material passing through the duct 100 is intercepted and a predetermined quantity of the same is deposited inside the collection cavity 4 and is held in position thanks to the presence of the support portion 11.

After a sufficient time has elapsed to ensure substantial filling of the measuring cavity 4, the control unit 22 moves the slide 3 through the mechanism 12 retracting it from the sliding seat 6.

In particular, the collection cavity 4 is precisely positioned (in axis) with respect to the head 5a of the microwave sensor 5, as illustrated in Figure 5.

The control unit 22 activates the vibration generator 16 in such a way that the material contained inside the collection cavity 4 is more compacted thanks to the movement bringing the smaller particles downwards.

During the whole phase of vibrating the slide 3, the microwave sensor 5 carries out continuous measurements, ie it carries out a plurality of successive readings of the signal.

The reading of the peak signal, which should correspond to the maximum density of the collected sample, is therefore considered as a reliable reading (except for filtering in the case of inconsistent signals).

Once the parameter value reading operations have been completed, the control unit interrupts the vibration action and moves the movement mechanism 12, so as to bring the slide back to the outside of the seat. sliding 6 towards the second extracted position shown in figure 3.

In this last position the predetermined quantity of material that was inside the collection cavity 4 is free to escape through the lower outlet 4B of the cavity itself, re-entering the main flow of material and it is therefore possible proceed with a new measurement operation.

During all handling phases, the gaskets 21 and 32, as well as the scraping element 18 help to keep the sliding seat 6 clean, avoiding jamming or misalignments of the device.

It should be noted that the microwave sensor 5, and in particular its head portion 5a, are never moved with respect to the fixed frame 2 and how the collection cavity 4 is always precisely positioned in correspondence with the flat portion 9a of the base wall 9 thanks to to the precision of movement guaranteed by the toothed belt 14.

The mechanical measures identified above contribute to considerably improving the accuracy and repeatability of the humidity reading. However, it should be noted that the control unit 22, through the management software, is programmed to carry out a preliminary calibration phase (before carrying out the on-line measurements during the standard working phases of the device), capable of further increasing reading accuracy.

In this regard, during the calibration phase, the control unit 22 is programmed to receive a plurality of measurements of the value of the parameter taken, by means of the microwave sensor 5, on different samples of the same material in powder or granules of which the real value of the parameter itself is known, for example as it has been measured with precise laboratory analyzes. In other words, a precise measurement of the humidity parameter of a material is carried out in the laboratory and then a series of successive measurements are carried out on a flow of the same material, whose humidity is known.

At this point the procedure is repeated in relation to a plurality (at least two) of humidity values (or of the parameter) of the material, always detecting and storing a series of experimental measurements obtained through the sensor 5 and comparing them with a laboratory value.

The control unit 22 is now programmed to process the detected data so as to minimize the error by means of a multiple linear regression of the data (for example, minimizing the error by means of an interpolation to the minimum squares).

Also the control unit 22 is programmed to perform a regression using support vectors (Support Vector Regression) on the same measured data.

The calibration phase therefore provides that the correction of the reading is completed by means of a linear combination, suitably weighted, between the Linear Multiple Regression of the measured values and the Support Vector Regression of the measured values so as to minimize the difference in reading of the device with respect to the value real (laboratory) parameter.

This calibration phase allows to minimize the effects of the variation in the density of the product in line linked to the differences in particle size, material formulation, measurement time, temperature and humidity itself of the various successive samples of the same material which obviously are not constant.

Furthermore, the control unit is programmed in such a way as to be able to determine, even experimentally, the respective weights of the linear combination of the aforementioned regressions in such a way as to be able to optimize the result.

Claims (10)

CLAIMS 1. Device for measuring parameters, such as density or humidity, of a powdered or granular material in a continuous stream of said material, the measuring device comprising: - a fixed support frame (2) which can be associated with a structure suitable for receiving a flow of material in powder or granules, said fixed frame (2) having a sliding seat (6) having an inlet (7), the sliding seat being delimited by at least one containment structure (8); - at least one slide (3) movable, relative to the fixed support frame (2), in the sliding seat (6) between a first position at least partially extracted with respect to the frame (2) and with respect to the sliding seat (6) and a position at least partially retracted with respect to the frame (2) towards the inside of the sliding seat (6), said slide (3) comprising at least one collection cavity (4) which, in the first extracted position of the slide (3), is at least partially inside the continuous flow to receive material in powder or granules and, in the retracted position of the slide (3), allows the measurement of parameters, and is contained in the sliding seat (6) of the fixed support frame ( 2); - at least one microwave sensor (5) for detecting a signal indicative of a value of said parameters, said sensor (5) being constrained to the fixed frame (2) in correspondence with the containment structure (8), the sensor (5 ) presenting a substantially flat head (5a) and the containment structure (8) presenting a base wall (9) equipped with a flat portion (9a) of constant thickness, the flat head (5a) of the microwave sensor (5) being arranged parallel, and in particular in contact, with the flat portion (9a) of the base wall (9) and being placed externally to the sliding seat, in the retracted position of the slide (3) the collection cavity (4) being positioned on the opposite side to the head (5a) of the microwave sensor (5) with respect to the base wall (9). 2. Device according to claim 1, in which the collection cavity (4) has an upper access (4a) and a lower exit (4b) connected to each other, the collection cavity (4) being a through-passage cavity to said slide (3), in particular the upper access (4a) having a smaller area than the lower exit area (4b), for example the collection cavity (4) presenting a cylindrical or truncated shape - conical. 3. Device according to the preceding claim, in which, in the retracted position of the slide (3), the lower outlet (4b) of the collection cavity (4) is in substantial contact with the base wall (9) in correspondence of said flat portion (9a), in particular there being no empty interstices between the lower outlet (4b) and the base wall (4) and / or between the head (5a) of the sensor (5) and the flat portion ( 9a) of the base wall (9). 4. Device according to any one of the preceding claims, in which the sliding seat has a passage section substantially counter-shaped to a corresponding section of the slide (3) to allow a back and forth translational movement of the slide (3) in the sliding seat itself, the device having a movement mechanism (12) to allow at least the movement between the first extracted position and the retracted position of the slide (3) and vice versa. 5. Device according to the previous claim, in which the movement mechanism (12) comprises at least one motor (13) coupled, directly or indirectly, to a belt (14), in particular toothed, movable around a predetermined number of pulleys ( 15), the slide (3) being constrained to said belt (14) to be correspondingly moved forward / backward inside the sliding seat (6), in particular the base wall (9) presenting an engagement seat (10) configured to receive and center the head (5a) of the sensor (5), the engagement seat being arranged externally to the sliding seat (6) and causing a thickness reduction, at least localized, of the base wall (9) , said engagement seat being in particular circular in shape. Device according to any one of the preceding claims, in which the fixed frame (2) has a support portion (11) emerging away from the base wall (9) with respect to the inlet (7) of the sliding cavity (6) , said support portion (11) cooperating with the collection cavity (4) in the first extracted position to avoid a leakage of a collected material from the lower outlet (4b), the slide (3) being movable towards at least a second position extracted in which the material in powder or granules can flow through the collection cavity (4) without being intercepted and confined in said collection cavity (4). Device according to any one of the preceding claims, further comprising a vibration generator (16) active on the slide (3) to generate a vibratory motion thereon, at least in the retracted position of the slide (3), in particular the vibration generator ( 16) being constrained to an engagement seat (17) obtained in a rear region of the slide (3). 8. Device according to any one of the preceding claims, further comprising: a scraper (18) active on the slide (3) in correspondence with the inlet (7) of the sliding seat (6), said scraper (18) having a scraping portion (18a) active at least on the upper surface and on the lower surface of the slide (3), said scraping surface (18a) being in particular active also in correspondence with the lateral surfaces of the slide (3) and defining a closed profile substantially counter-shaped to a cross section of the slide (3); And - optionally a mounting frame (19) of the scraper (18), said mounting frame (19) being engaged to the fixed frame (2) at the inlet (7) and having a through hole (20) configured to allow a crossing by the slide (3), the scraper (18) being interposed between the mounting frame (19) and the fixed frame (2) and having a respective through hole of overall dimensions preferably slightly smaller than the overall dimensions of the through hole (20) of the frame (19), in particular the mounting frame (19) having an external front seat for receiving a gasket (21). 9. Device according to any one of the preceding claims, further comprising a control unit (22) configured to receive the signal indicative of the value of said parameter and to determine a reading of the same parameter, the control unit (22) being programmed to carry out a plurality of successive readings of the signal during the vibration phase, in particular to establish a peak reading of the value, optionally the control unit (22) being active on a movement mechanism (12) to move said slide ( 3) between the first and / or second extracted position and / or retracted position and possibly to activate a vibration generator (16) active on the slide (3). 10. Device according to any one of the preceding claims, further comprising a control unit (22) configured to receive the signal indicative of the value of said parameter and to determine a reading of the same parameter, the control unit (22) being programmed to carry out a calibration phase to obtain a more accurate measurement, in said calibration phase the control unit (22) being programmed to receive a plurality of measurements of the parameter value taken, by means of the microwave sensor (5) , on different samples of the same powder or granule material of which the real value of the parameter is known, for example by laboratory analysis, the control unit (22) being programmed to carry out the calibration phase by means of a combination linear, suitably weighted, between a multiple linear regression of the measured values and a Support Vector Regression of the measured values to minimize a d reading difference of the device with respect to the real value of the parameter.