Method for determining gain of acoustic transducer

Abstract

A method for adjusting the gain of an ultrasound probe implementing a probe (1) comprising: a measurement transmitter (11) configured to transmit incident ultrasound waves in a liquid metal; a receiver (21) configured to detect ultrasonic waves reflected or diffracted by the liquid metal after emission of the incident ultrasonic waves; a processing unit (32) configured to amplify the detection signal according to the gain (). The measurement transmitter and the receiver are immersed in or arranged opposite a reference medium (6) comprising a target (7). The method includes moving the target at different measurement locations opposite the probe. The gain is adjusted according to the number of positions where the amplitude of the detection signal is within a predetermined range.

Description

Technical Field

[0001] The technical field of this invention is to characterize liquid metal castings using ultrasound, such as aluminum alloy castings. Background Technology

[0002] In the field of metal casting, it is necessary to inspect the quality of molten metal to detect inclusions. This is especially true for aluminum. Some aluminum alloy products, such as can stock, have very high requirements for inclusion content. These inclusions are generated during the melting, manufacturing, and casting processes when these alloys are in the liquid phase. The quality of molten metal is determined by the amount of inclusions present in the metal. These inclusions can consist of oxides, nitrides, carbides, fluorides, or borides. Common inclusions encountered in molten aluminum include Al₂O₃, MgAl₂O₄, Al₄C₃, MgO, CaO, CaF₂, TiB₂, TiVB₂, and SiO₂ particles. Their sizes range from a few micrometers to several hundred micrometers.

[0003] The quality of castings can be monitored online using ultrasonic measurement technology. In this type of measurement, ultrasonic waves propagate through the molten metal. If inclusions are present, some of the emitted sound waves are reflected and can be detected. The amplitude of the reflected or diffracted waves can be used to determine the size of the inclusions in the metal. Ultrasonic technology enables the characterization of a portion of the molten metal in castings, typically 2% when inspected in a tank transporting the molten metal from the furnace toward the casting pit.

[0004] Probes that allow for the measurement of castings using ultrasound have been described in patents EP3204764B1 and EP3204763B1.

[0005] Document EP1194772B1 describes a method for calibrating a probe in which reflectors are disposed at the ends of rods, which are then placed in liquid metal. The reflectors can have different sizes. Therefore, a correlation can be established between the size of each reflector and the amplitude of the detected sound wave. This method needs to be applied to each probe individually. Furthermore, it implies setting the calibrated reflectors in liquid metal, which can become complex.

[0006] Another possibility for estimating inclusion size is to use a correlation curve between measurements obtained using an ultrasonic probe and measurements obtained using a method considered as a reference method. For example, the reference method could be a "LIMCA" (Liquid Metal Cleanliness Analysis) type analytical method, based on the analysis of the electrical resistance of a sample of liquid metal. It could also consist of a method described in EP1194772B1, which involves calibrating a reflector. Therefore, a correlation function can be established between the inclusion size measured by the reference method and the amplitude of the ultrasonic signal.

[0007] In “In Situ Detection of Non-metallic Inclusions in Aluminum Melt (1xxx) - Comparison between a newly developed ultrasonic technique and LiMCA and PoDFA method” (Light Metals 2019, January 1, 2019, pp. 1623-1629), F. Feikus et al. describe the development of a method for detecting non-metallic inclusions in cast or machined aluminum products based on ultrasonic technology. The document acknowledges the challenges of calibration, noting in paragraph 2 on page 1629: “The greatest challenge to date has been the calibration of the ultrasonic system, which still requires further research.”

[0008] One difficulty associated with using ultrasound probes is that their responses can differ from one another. However, calibrating each probe using a reference method (such as the LIMCA-type reference method or the reference method described in EP1194772B1) is challenging. Indeed, such calibration takes time, regardless of the reference method chosen.

[0009] Matthias Messer's “PULSED UL TRASONIC DOPPLER VELOCIMETRY FORMEASUREMENT OF VELOCITY PROFILES IN SMALL CHANNELS AND CAPPILARIES” (GTLibrary Collections Theses and Dissertations, August 8, 2005) describes the limitations of pulsed ultrasonic Doppler velocimetry in measurements, particularly in cases where the channel has a relatively small thickness relative to the transducer diameter, the flow velocity is low, and a backflow region exists.

[0010] The variability in response between two probes with identical structures is particularly attributable to differences that may affect the electronic circuitry or the materials used. When encountering the same inclusion, two probes with identical but different designs may produce detection signals of different amplitudes due to the variability in probe response.

[0011] It is preferable, or even necessary, to consider this variability, for example, if one seeks to apply the same correlation curve to measurements produced by different ultrasound probes.

[0012] The inventors have proposed a method that allows for consideration of the variability in the responses of different probes. The aim is to design identical probes to produce the same signal, or to treat them as producing the same signal, in the presence of the same inclusions. Summary of the Invention

[0013] The first object of the present invention is a method for adjusting the gain of an ultrasonic probe, the probe comprising: - A measuring transmitter configured to emit incident ultrasonic waves in liquid metal; - A receiver configured to detect ultrasonic waves reflected or diffracted by inclusions in the liquid metal after the incident ultrasonic waves are emitted, and to form a detection signal based on the detected ultrasonic waves. - A processing unit configured to amplify the detection signal according to the gain; The method includes the following steps: a) The probe is positioned such that the measuring transmitter and the receiver are immersed in or positioned opposite the reference medium, the reference medium being in liquid or gel form, the reference medium including a target positioned at the measuring location, the target being formed of a solid material; b) Powering the measuring transmitter so that it emits incident ultrasonic waves propagating in the reference medium; c) The receiver detects a detection signal representing the ultrasonic wave reflected by the reference medium under the action of the incident wave; The method is characterized in that it further includes: d) Repeat steps a) to c) during different measurement time points, such that at each measurement time point, the target moves to a different measurement position, the measurement positions forming a grid in the reference medium; e) Determine the measurement amplitude at each measurement location based on each signal detected during each step c). f) Select a measurement location where the measurement amplitude is within a predetermined range; g) Count the number of measurement locations selected in step f), compare the number of counted locations with a predetermined reference value, and then adjust the gain so that: - When the number of selected measurement locations is lower than the reference value, increase the gain; - When the number of selected measurement locations is higher than the reference value, the gain is reduced.

[0014] Based on one possibility: - After step e), the measured amplitude is between the minimum amplitude and the maximum amplitude; - The predetermined amplitude range is between a first fraction of the maximum amplitude and a second fraction of the maximum amplitude, wherein the second fraction of the maximum amplitude is strictly lower than the first fraction of the maximum amplitude.

[0015] The first fraction with the largest amplitude can be equal to 1.

[0016] The second score with the largest amplitude can be between 0.2 and 0.8.

[0017] Preferably, after step g), if the number of selected measurement locations differs from the reference value, steps a) to g) are repeated after adjusting the gain.

[0018] The method may include performing steps a) to f) using a reference probe prior to step g), such that the number of measurement locations obtained in step f) using the reference probe corresponds to the reference value considered in step g).

[0019] According to one possibility, the target is a bead-like object with a diameter between 1 mm and 10 mm.

[0020] One possibility is that the reference medium is water or includes water.

[0021] According to one possibility, - The measurement transmitter is coupled to a first waveguide immersed in the reference medium; - The receiver is coupled to a second waveguide immersed in the reference medium.

[0022] The grid can define different measurement locations distributed along the vertical, lateral, and horizontal axes, which are orthogonal in pairs. In step d), the target can be translated along the vertical axis for different coordinates along the lateral and horizontal axes.

[0023] Based on one possibility: - For the same coordinates along the lateral and transverse axes respectively, each translation along the longitudinal axis is performed in both the departure and return directions; - At each coordinate along the lateral axis and the transverse axis, at least one measurement amplitude is determined, which corresponds to the maximum amplitude measured during the translation in the departure direction and / or return direction.

[0024] According to one possibility, in step d), the target (7) is moved by scanning, so that steps a) to c) are performed without fixing the target.

[0025] Another object of the present invention is an ultrasonic probe comprising: - A measuring transmitter (11) configured to emit incident ultrasonic waves in the liquid metal; - A receiver configured to detect ultrasonic waves reflected or diffracted by the liquid metal after the incident ultrasonic waves are emitted, and to form a detection signal based on the detected ultrasonic waves; - Processing unit (32), the processing unit being configured to adjust according to gain ( The detection signal is amplified, and the measurement amplitude is determined based on the detection signal obtained from the receiver; - The device is characterized in that, based on the measurement amplitude determined when the target formed of solid material is arranged in the reference medium, opposite the probe, and at different measurement positions, the processing unit is configured to implement steps e) to g) of the method according to the first objective of the invention.

[0026] The probe may include a control unit configured to control the movement of the target between different measurement positions and transmit the measurement positions to a processing unit.

[0027] The invention will be better understood by reading the disclosure of the embodiments presented in the following description in conjunction with the accompanying drawings. Attached Figure Description

[0028] Figure 1A A first embodiment of the probe that enables the implementation of the present invention is shown.

[0029] Figure 1B Another embodiment of the probe that enables the implementation of the present invention is shown.

[0030] Figure 2 The diagram schematically illustrates the sound waves detected at a single measurement point in time.

[0031] Figure 3 The main steps of the method according to the invention are illustrated schematically.

[0032] Figure 4AAn example is illustrated of a bead-shaped target arranged opposite the probe during the implementation of the method according to the invention.

[0033] Figure 4B The diagram illustrates how the target is moved sequentially to different measurement positions.

[0034] Figure 4C The amplitudes measured at different locations on the target are shown.

[0035] Figure 4D yes Figure 4C Detailed images.

[0036] Figure 4E yes Figure 4D Detailed images.

[0037] Figure 5 The measured amplitude is shown. Correlation curve between the known inclusion size and the known inclusion size. Detailed Implementation

[0038] The first embodiment of the ultrasonic probe that enables the implementation of the present invention has been combined Figure 1A As shown. The probe includes a measuring transmitter 11 and a receiver 21. In this embodiment, the measuring transmitter 11 and receiver 21 are formed by the same acoustic transducer. For example, the acoustic transducer is a piezoelectric transducer known to those skilled in the art.

[0039] For example, the transducer is a piezoelectric material wafer that emits sound waves at a frequency of 15 MHz. Typically, the frequency of the emitted sound waves is preferably between 1 MHz and 20 MHz.

[0040] This probe is designed to detect inclusions 4 in a liquid medium 2 to be analyzed, more specifically, to detect inclusions 4 in liquid metal, such as an aluminum alloy. Figure 1A and Figure 1B In the diagram, the horizontal dashed line represents the interface between liquid metal 2 and the ambient medium 3, such as air.

[0041] The probe 1 includes a waveguide 13 designed to be immersed in liquid metal 2. This waveguide is configured to facilitate the propagation of acoustic waves between the transducer, which acts as a transceiver, and the liquid metal 2. For example, the waveguide 13 is formed of a silicon nitride or silicon oxynitride (SiAlON) type material, or more generally of a metallic or refractory ceramic type material, which are considered inert relative to the liquid metal 2. The use of such a waveguide has been described in EP3204763B1 or EP1194772B1.

[0042] exist Figure 1A and Figure 1BThe ultrasonic field 5 is schematically shown, corresponding to a portion of the liquid metal being examined by the probe 1. When the inclusion 4 passes through the ultrasonic field, a portion of the sound waves emitted by the measuring transmitter 11 is reflected or diffracted toward the receiver 21. The characteristics of the reflected waves, particularly their amplitude, enable the detection and characterization of the inclusions, such as estimating their size.

[0043] Preferably, the probe may include a power transmitter 12 configured to emit high-power acoustic waves, i.e., above 10W, preferably above 100W, such as 120W, as described in EP3204764. In practice, applying high-power acoustic waves allows for the wetting of the first waveguide 13 by the liquid metal 2. The power transmitter 12 is activated at regular time intervals to ensure that good wetting of the waveguide 13 by the liquid metal 2 is maintained continuously.

[0044] Figure 1B A preferred configuration is shown, in which the probe includes a measuring transmitter 11 and a receiver 21. The measuring transmitter 11 is connected to a first waveguide 13. The receiver 21 is connected to a second waveguide 23, which is preferably identical to the first waveguide 13 (same material, same dimensions), but different from the first waveguide 13. For example, the length of each waveguide is between 10 cm and 50 cm. Preferably, the first and second waveguides are straight and extend around a first central axis Δ1 and a second central axis Δ2, respectively. The central axes Δ1 and Δ2 intersect and are inclined relative to each other according to an angle α. For example, this angle is between 25° and 35°. For example, angle α is equal to 28°. This configuration has been described in EP3204764B1.

[0045] In this embodiment, the probe may include a first power transmitter 12 and a second power transmitter 22, as described in conjunction with the first embodiment. The first and second power transmitters are periodically activated to improve the wetting of the liquid metal 2 on the first waveguide 13 and the second waveguide 23, respectively.

[0046] The probe includes a control unit 31 configured to control the measuring transmitter 11 to emit sound waves, and when the probe includes a power transmitter 12, to control the power transmitter 12 to emit power sound waves.

[0047] The sound waves emitted by the measuring transmitter 11 are typically emitted in series. In practice, each series of sound waves is emitted by the measuring transmitter 11 at a regular frequency (e.g., 10 Hz). A series includes at least one sound wave, preferably several consecutive sound waves. Within the same series, the emission frequency of the sound waves can be between 100 Hz and 300 Hz, corresponding to the excitation frequency of the piezoelectric transducer of the measuring transmitter. Figure 2The diagram schematically illustrates three waves detected by receiver 21 after transmitter 11 emits a series of three waves. Parentheses indicate that the three waves belong to the same series. Figure 2 In the diagram, the vertical axis corresponds to the signal S(t) detected by receiver 21, while the horizontal axis corresponds to time t.

[0048] The probe includes a processing unit 32 configured to process the detection signal S(t) received from receiver 21. Processing unit 32 includes an amplifier designed to amplify the detection signal from receiver 21, and the amplifier's amplification gain G0 is typically set at the factory after the probe is manufactured. Gain G0 can be adjusted as described below. Gain G0 is a multiplication term applied to the detection signal. It is important to note that, as explained on page 25 of Messer's paper, gain G0 (also known as total gain) should not be confused with sweep gain (or time-gain compensation (TGC) or time-varying gain (TVG)). Total gain is a constant gain level independent of the depth of the sampling volume. Time-varying gain (TGC or sweep gain) is used to compensate for beam attenuation by amplifying the echo signal from the far-end structure more than the echo signal from the near-end structure.

[0049] Processing unit 32 is configured to calculate the amplitude of the detected signal after amplification. The calculated amplitude can be the average of the maximum amplitudes of each detected sound wave, or the maximum amplitudes of all sound waves detected after a series of wave emissions. The calculated amplitude is then labeled as follows: . The measurement time corresponds to the detection of a series of sound waves by the receiver 21.

[0050] The processing unit may include one or more microprocessors or electronic circuits. Each microprocessor or electronic circuit is configured to process the detection signal and perform an operation selected from: determining the measured amplitude, amplifying the signal, or one of the steps described below.

[0051] The presence of large inclusions in liquid metal can lead to amplitude. Changes have occurred. The magnitude of the change... It allows for the estimation of inclusion size based on correlation curves plotted experimentally using reference methods (such as the LIMCA method or methods based on calibrated reflectors, which are described in conjunction with existing techniques).

[0052] The same correlation curve can be used for different ultrasound probes with the same design, provided that the amplitudes obtained from the ultrasound probes are comparable. However, as previously noted, it is necessary to consider the variability of the probes, even if they are similar to each other: the same size and using the same materials.

[0053] Probe 1 is designed to be immersed in liquid metal 2. For example, the liquid metal may flow from a furnace or be present in a ladle or crucible. Alternatively, the liquid metal may flow into a tank. One or more waveguides of the probe are immersed in the tank. The probe may be positioned directly at the furnace outlet or further downstream, at the outlet of a filter or deaerator. This filter may consist of a deep bed filter, a ceramic foam filter (CFF), or any other type of filter.

[0054] Due to cost and time constraints, it is impractical to generate correlation curves for each probe using a reference method. However, it is necessary to consider the variability in the response of each probe. The inventors propose a method for obtaining comparable responses for several probes, enabling the use of the following combination... Figure 3 The correlation curve described.

[0055] The main steps of this method are as follows: Figure 3 Example in.

[0056] Step 100 The target is placed in the reference medium at the initial measurement position.

[0057] During this step, target 7 is positioned in the reference medium 6 at a predetermined initial measurement position relative to the probe. Place.

[0058] The target 7 is designed to reflect the incident acoustic waves emitted by the probe's measuring transmitter toward the receiver 21. The target 7 is formed of a solid material (e.g., metal or ceramic, such as synthetic sapphire). The target can be a solid spherical bead with a diameter less than 15 mm or 10 mm, for example, equal to 4 mm. Given the difference in acoustic impedance between water and aluminum, a diameter of 4 mm is considered to correspond to an ultrasonic signal equivalent to a diameter of 100 µm in liquid aluminum. A size of 100 µm corresponds to the typical inclusion size to be detected in liquid aluminum.

[0059] Typically, the target 7 is contained within a spherical volume with a diameter less than or equal to 15 mm or 10 mm. The target can be fixed to the end of the rod 8. Preferably, the rod is thin and formed of a low-echo material. Advantageously, the material forming the target 7 or the rod 8 is compatible with implementations in liquid metal (e.g., alumina).

[0060] The target is positioned within the focal region 9 of the probe in the reference medium. The focal region 9 corresponds to an area where, under the influence of sound waves emitted by the transmitter 11, detectable sound waves reach the receiver 21. The focal region depends on the medium being analyzed; it differs from... Figure 1B The focal area 4 is shown in the image. Figure 4A In the diagram, the focal region 9 is schematically shown with a dashed outline.

[0061] One advantage of this invention is that the reference medium 6 can be different from liquid metal. For example, it can consist of a liquid medium (e.g., water) at ambient temperature. It can also be a medium with gel consistency, but it should be remembered that it is preferred that the reference medium is liquid. Another advantage of this invention is that the liquid medium and the target are easy to handle. Preferably, the liquid medium is maintained at ambient temperature, or at a temperature where there are no limitations in use, preferably below 80°C.

[0062] Step 110 : To take measurements.

[0063] During measurement time The measurement is performed, and the measurement time corresponds to the measurement position occupied by the target at that measurement time point. . It is a natural integer indexed at each measurement time point. At the initial measurement location, = 0. The measurement corresponds to the emission of a sound wave or a series of sound waves by the transmitter 11, and the formation of a detection signal by the receiver 21. Combining Figure 2 An embodiment of the detection signal has been described. The processing unit 32 determines the measurement amplitude based on the amplified detection signal. .

[0064] Step 120 : Moving target.

[0065] During step 120, target 7 is moved to index 120. +1 another measurement location. Then, step 110 is repeated, such that during the repetition of steps 110 and 120, target 7 is continuously arranged at different predetermined measurement locations. The measurement location A spatial grid, such as a regular grid, is described in reference medium 6. Preferably, the grid is a three-dimensional grid. Figure 4B Different measurement locations are shown, uniformly distributed within a 3D mesh describing a parallelepiped. The grid is defined along the vertical axis X, the lateral axis Y, and the horizontal axis Z.

[0066] Preferably, the movement of target 7 is controlled by control unit 33, which is programmed to control the movement of the bead within a predefined spatial grid. Preferably, the control unit is connected to processing unit 32 to provide different positions of the target.

[0067] Step 130 Collect the measurement amplitude at each measurement time point.

[0068] During step 130, data is collected for each measurement location. Measurement range at the location The amplitude Between the maximum amplitude and minimum amplitude (corresponding to the noise level here) )between. Figure 4C It is shown that, according to, Figure 4B The different amplitudes measured during the three-dimensional mesh scanning of the target are shown. The target has moved within the plane defined by axes X and Y by continuous translation parallel to the vertical axis X at a speed of 10 mm / s. Measurements were acquired at a frequency of 50 Hz. During each translation parallel to the vertical axis X, the amplitude measured at 50 Hz corresponds to the average of three consecutive pulses detected at 500 Hz. Figure 4B In the diagram, the dashed line schematically illustrates the translation along axis X. Target 7 moves by scanning, enabling amplitude acquisition without the need for a fixed target. In this way, this configuration is comparable to that used when characterizing liquid metal castings: during measurement, the inclusions are in motion and measured by a fixed probe.

[0069] The grid extends 100 mm parallel to the vertical axis X, 30 mm along the lateral axis Y, and 50 mm along the horizontal axis Z. Within the XY plane, translations have been performed parallel to the axis Y based on the departure / return travel along the same line. The maximum measurement amplitude has been preserved during each translation parallel to the vertical axis X. Therefore, two amplitude values ​​have been extracted during the departure / return travel along the same line parallel to the axis X, corresponding to the maximum amplitude measured during the departure and return travels, respectively. The two extracted maximum amplitudes are assigned to the coordinates Y and Z for the translation. Two consecutive translations along the axis X have been offset by 1 mm along the axis Y. Each scan within the XY plane has been performed based on a constant coordinate along the axis Z. After each scan within the same XY plane along the axis Z, the target has moved along the axis Z in spatial steps of 6 mm.

[0070] exist Figure 4C In the image, the seven lobes marked in parentheses are distinguished, each corresponding to an amplitude measured during the XY plane scan at one of ten different coordinates along the Z-axis: Z1, Z2, Z3, Z4, Z5, Z6, Z7, Z8, Z9, and Z10. The lobes are spaced 6 mm apart along the continuous Z-axis. Each lobe is composed of elements exceeding the noise value. And the amplitude was measured based on the scanning of the X and Y axes. form.

[0071] exist Figure 4C In the diagram, the vertical axis corresponds to the measurement amplitude, which is normalized to maximize the measurement amplitude. The value is close to 80. The horizontal axis corresponds to the measurement time point.

[0072] Figure 4D yes Figure 4C The detailed diagram shows the lobe corresponding to coordinate Z4. Figure 4D The coordinates Y1, Y2, Y3, Y4, Y5, Y6, Y7, Y8, Y9, ... 8, The amplitude measured during the departure / return stroke of Y9 parallel to axis X. At each coordinate along the Y-axis, two maximum values ​​recorded during the departure and return journeys, respectively, have been retained.

[0073] Figure 4E yes Figure 4D The detailed diagram corresponds to the departure / return journey along axis X at coordinate Y5. Two peaks are distinguished, corresponding to the central portion of the target passing through the focal region 9, where the amplitude of the detected signal is greatest. The first peak corresponds to the departure journey during the target's translation parallel to axis X, and the second peak corresponds to the return journey. As previously stated, the value of each peak is extracted and considered to represent the measurement position corresponding to coordinates Y5, Z4. Therefore, in this particular embodiment, two measurement amplitudes are assigned for each coordinate along axes Y and Z, corresponding to the maximum amplitude detected during the departure and return translations, respectively.

[0074] Step 140 Select the measurement location.

[0075] During step 140, those whose amplitude was measured during the 3D scan are selected. Within the predetermined range The measurement location within. For example, the amplitude range. Fixed at maximum amplitude First score and maximum amplitude The first fraction is greater than the second fraction. For "fraction," it should be understood as a positive real number less than or equal to 1. The first fraction is strictly greater than the second fraction. For example, the first fraction equals 1, and the second fraction equals 0.5. Then the range of magnitude... Corresponding to the maximum amplitude and maximum amplitude The range is between 50% and 1. Typically, the first score is between 0.8 and 1, and the second score is between 0.2 and 0.8.

[0076] Then, the selected measurement amplitude Within the range Measurement location inside Perform the counting.

[0077] Step 150 Selected measurement locations Quantity and reference value Compare them.

[0078] During this step, the measurement location selected in step 140 will be... quantity Compared with reference value Compare them.

[0079] Reference values ​​can be established experimentally beforehand by using one or more reference probes and performing steps 100 to 140 with the same scanning parameters. Preferably, the reference probe is structurally identical to the probe for which gain adjustment is sought. When the measurement position selected in step 140... of Below the reference value At that time, that is At that time, increase the probe gain .

[0080] When the measurement position selected in step 140 of Higher than the reference value At that time, that is At that time, reduce the probe gain. .

[0081] Step 160 :repeat.

[0082] After increasing or decreasing the gain, it is preferable to repeat steps 100 to 150, taking into account the gain updated during previous iterations. The value of .

[0083] Selected measurement location quantity Corresponding to the reference quantity At that time, the gain is considered The value is correct. The number of measurement locations selected at this point corresponds to the reference number, possibly taking into account predetermined uncertainties, such as... or . For example, equal to 10%.

[0084] The selection or calculation described in steps 130 to 150 is performed by processing unit 32. The term "processing unit" should be considered in a broad sense. The processing unit refers to a computing device that enables the implementation of the present invention. It may consist of a single microprocessor or multiple different microprocessors, each assigned one or more tasks.

[0085] The processing unit 32 can be connected to the control unit 33, which allows control of the target's movement. In this case, the control unit transmits the target's position to the processing unit 32.

[0086] After implementing this invention, all probes are considered to have the same response. The response of one of them can be associated with a typical LIMCA-type method or the method described in EP1194772B1.

[0087] Combination Figure 3 The described steps have been performed by executing five consecutive scans using the same reference probe. Therefore, steps 110 to 120 have been repeated by performing five scans labeled T1, T2, T3, T4, and T5. During each scan, the maximum amplitude... The value has been normalized to 55%, and the number of measurement locations with amplitudes between the maximum amplitude and half of the maximum amplitude has been determined. After scanning, the number of measurement locations selected during each scan period has been determined. Calculate the average value.

[0088] Table 1 shows the results obtained. The last column corresponds to the number of measurement locations selected during each scan. . Table 1 Then, the average value of 30.2 has been regarded as a reference value. .

[0089] Then, another probe, different from the reference probe, was implemented. Regarding gain... Five scans, identical to those performed for the reference probe, were performed to measure different values. The average value of the measurement positions where the measurement amplitude was between the maximum amplitude and half of the maximum amplitude was then calculated. The probe gain has been adjusted. This makes the quantity Corresponding to the reference quantity determined by the reference probe .

[0090] Table 2 shows the results obtained. Table 2 What was observed was that, in order to increase the quantity Considered equal to (Constrained by a predetermined uncertainty range), gain It should be equal to 57.4 dB.

[0091] Adjust the gain as before. Allow the use of, for example Figure 5 The correlation curve is shown schematically. This correlation curve was plotted experimentally using the reference probe. Therefore, the vertical axis corresponds to the measurement amplitude related to the known inclusion size. The horizontal axis corresponds to dimensions, such as diameter.

[0092] When the probe is implemented on the liquid metal, the probe is arranged such that the longitudinal axis X considered in steps 120 and 130 corresponds to the axis along which the liquid metal flows.

[0093] Figure 5 Points are shown, each corresponding to an experimental measurement. A correlation curve obtained by adjusting the experimental points has also been plotted with a dashed line.

[0094] The correlation function thus plotted can be applied to amplitudes obtained from different probes for which the gain has been adjusted as previously described, such that the response of each probe is comparable to that of the reference probe.

[0095] This invention can be applied by implementing an ultrasonic probe of the same type as the reference probe (i.e., having the same structure, the same implementation method, and the same manufacturing process).

Claims

1. A method for adjusting the gain of an ultrasonic probe, the probe comprising: - A measuring transmitter (11) configured to emit incident ultrasonic waves in liquid metal; - Receiver (21), the receiver being configured to detect ultrasonic waves reflected or diffracted by inclusions in the liquid metal after the incident ultrasonic waves are emitted, and to form a detection signal (S(t)) based on the detected ultrasonic waves. - Processing unit (32), the processing unit being configured to adjust according to the gain ( Amplify the detection signal; The method includes the following steps: a) The probe is positioned such that the measuring transmitter and the receiver are immersed in a reference medium (6), or positioned opposite the reference medium, which is in liquid or gel form, and includes components positioned at the measuring location ( The target (7) is formed of a solid material; b) Power is supplied to the measuring transmitter (11) so that the measuring transmitter emits incident ultrasonic waves propagating in the reference medium; c) The receiver detects a detection signal representing the ultrasonic wave reflected by the reference medium under the action of the incident wave; The method is characterized in that it further includes: d) At different measurement time points ( During this period, steps a) to c) are repeated, such that at each measurement time point, the target (7) moves to a different measurement position. The measurement locations form a grid in the reference medium; e) Determine each measurement location based on each signal detected during each step c). The measurement amplitude of ) ); f) Select the measurement amplitude within a predetermined amplitude range ( Measurement location within ) ); g) The number of measurement locations selected in step f) ) is counted, and the number of counted positions is compared with a predetermined reference value ( The comparison is performed, and then the gain is adjusted so that: - When the number of selected measurement locations is lower than the reference value, increase the gain; - When the number of selected measurement locations is higher than the reference value, the gain is reduced.

2. The method according to claim 1, wherein: - After step e), the measured amplitude is between the minimum amplitude and the maximum amplitude; - The predetermined amplitude range is between a first fraction of the maximum amplitude and a second fraction of the maximum amplitude, wherein the second fraction of the maximum amplitude is strictly lower than the first fraction of the maximum amplitude.

3. The method of claim 2, wherein the first fraction of the maximum amplitude is equal to 1.

4. The method of claim 3, wherein the second fraction of the maximum amplitude is between 0.2 and 0.

8.

5. The method according to any one of the preceding claims, wherein after step g), if the number of selected measurement positions differs from the reference value, steps a) to g) are repeated after adjusting the gain.

6. The method according to any one of the preceding claims, comprising, prior to step g), performing steps a) to f) using a reference probe, such that the number of measurement locations obtained in step f) using the reference probe corresponds to the reference value considered in step g). ).

7. The method according to any one of the preceding claims, wherein the target (7) is a bead with a diameter between 1 mm and 10 mm.

8. The method according to any one of the preceding claims, wherein the reference medium (6) is water or includes water.

9. The method according to any one of the preceding claims, wherein: - The measurement transmitter is coupled to a first waveguide (13) immersed in the reference medium; - The receiver is coupled to a second waveguide (23) immersed in the reference medium.

10. The method according to any one of the preceding claims, wherein the grid defines different measurement locations distributed along the longitudinal axis (X), lateral axis (Y), and transverse axis (Z), the lateral axis, longitudinal axis, and transverse axis being orthogonal in pairs.

11. The method of claim 10, wherein in step d), the target is capable of translating along the longitudinal axis (X) for different coordinates along the lateral and transverse axes.

12. The method according to claim 11, wherein: - For the same coordinates along the lateral and transverse axes respectively, each translation along the longitudinal axis is performed in both the departure and return directions; - At each coordinate along the lateral axis and the transverse axis, at least one measurement amplitude is determined, which corresponds to the maximum amplitude measured during the translation in the departure direction and / or return direction.

13. The method according to any one of the preceding claims, wherein in step d), the target (7) is moved by scanning, such that steps a) to c) are performed without fixing the target.

14. An ultrasonic probe, comprising: - A measuring transmitter (11) configured to emit incident ultrasonic waves in the liquid metal; - Receiver (21), the receiver being configured to detect ultrasonic waves reflected or diffracted by the liquid metal after the incident ultrasonic waves are emitted, and to form a detection signal based on the detected ultrasonic waves; - Processing unit (32), the processing unit being configured to adjust according to gain ( Amplify the detection signal and determine the measurement amplitude based on the detection signal obtained from the receiver; - The device is characterized in that, based on the measurement amplitude determined when the target formed of solid material is arranged in the reference medium, opposite the probe, and at different measurement positions, the processing unit is configured to implement steps e) to g) of the method according to any one of the preceding claims.

15. The ultrasonic probe of claim 14, comprising a control unit (33) configured to control the movement of the target between different measurement positions and to transmit the measurement positions to the processing unit (32).

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