Calibration method of ultrasonic measuring device

Abstract

The invention relates to a method for calibrating an ultrasonic measuring device, in particular an ultrasonic bolt testing device, comprising the following steps: a) providing a reference object; b) measuring the reference object via an ultrasonic measuring device to determine reference measurement data representative of an ultrasonic length of the reference object; c) storing the reference measurement data; d) measuring the reference object with the same or another ultrasonic measuring device in order to determine verification measurement data representative of the ultrasonic length of the reference object; e) comparing a reference length of the reference object determined on the basis of the reference measurement data with a verification length of the reference object determined on the basis of the verification measurement data; f) adjusting the ultrasonic measurement device on the basis of the comparison of the reference measurement data and the verification measurement data.

Description

[0001] The present invention relates to a method for calibrating an ultrasonic measuring device, in particular but not limited to a method for calibrating an ultrasonic bolt testing device. Another aspect of the present invention relates to an ultrasonic measuring device for determining the ultrasonic length of an object (preferably but not limited to a bolt).

[0002] As the size and number of wind turbines worldwide increase, so too does the demand for critical loads to be transferred via bolted connections. This increase in transferred loads requires that bolted joints be installed very precisely, i.e. that the clamping force is at the appropriate level and that the flanges fit perfectly. This force creates friction between the clamping surfaces, preventing them from slipping. If the required clamping force is not achieved, these surfaces may slip, placing unnecessary loads on the bolted joint. This can eventually lead to failure of the bolted joint and, ultimately, the entire connection. To ensure the correct clamping force, high-precision tools such as torque wrenches have been developed. Although torque wrenches are very precise in applying the required torque, the resulting clamping force is heavily affected by friction and relaxation.

[0003] Friction and relaxation depend on factors such as lubricant, material, surface treatment, geometry and production tolerances. Even if the same force is applied to the same bolt, the resulting clamping force will vary. In theory, the variation can be up to ±30%, but in practice variations of up to 70% have been determined.

[0004] In order to avoid large discrepancies, ultrasonic measuring devices have been developed that can accurately determine the clamp load. This ultrasonic measuring device measures the elongation of each bolt after tightening. The elongation is a direct measure of the clamp force and is not affected by any tightening factors. This ultrasonic measuring device can be used for verification after tensioning as well as during tensioning.

[0005] Although the aforementioned ultrasonic measuring devices can determine the elongation of the bolt very accurately, the measurement results of the ultrasonic measuring device may change during the service life of the device, for example due to wear. In addition, the use of different hardware for measurement may lead to measurement deviations. In order to ensure that the ultrasonic measuring device provides accurate and comparable readings throughout its service life, regular recalibration is required.

[0006] Calibration is usually performed using reference / calibration rods, where the operator must manually enter the specifications of the rods to obtain a comparable calibration.

[0007] Recalibration using this known method requires the operator to enter / select various parameters of the calibration rod, such as the speed of sound within the calibration rod and its physical length. Such calibration rod parameters are usually provided in a data sheet for the calibration rod, along with several other (now irrelevant to the calibration) characteristics of the calibration rod. Therefore, the operator may easily enter the wrong parameters, which may affect the recalibration and lead to inaccurate future measurements.

[0008] The present invention attempts to solve or at least improve one or more of the above problems. Specifically, the object of the present invention is to provide a simple and reliable method for calibrating an ultrasonic measuring device. Another object of the present invention is to transfer the burden of data input from the operator to the device manufacturer to avoid unnecessary errors.

[0009] The above objects of the invention are solved by the method of independent claim 1 and the ultrasonic measuring device of independent claim 15. Further embodiments are disclosed in the attached dependent claims.

[0010] According to a first aspect of the present invention, a calibration method for an ultrasonic measuring device, in particular an ultrasonic bolt testing device, is provided, the method comprising the following steps:

[0011] a) Provide reference objects;

[0012] b) measuring the reference object via an ultrasonic measuring device to determine reference measurement data representing the ultrasonic length of the reference object;

[0013] c) storing the reference measurement data;

[0014] d) measuring the reference object using the same or another ultrasonic measuring device to determine verification measurement data representing the ultrasonic length of the reference object;

[0015] e) comparing a reference length of the reference object determined based on the reference measurement data with a verification length of the reference object determined based on the verification measurement data;

[0016] f) adjusting the ultrasonic measurement device based on the comparison result of the reference measurement data and the verification measurement data.

[0017] According to the present invention, a reference object is measured to generate reference measurement data representing the ultrasonic length of the reference object, and verification measurement data is generated at a later point in time. The original measurement result (i.e., the determination of the reference measurement data) is preferably determined by the manufacturer and stored in a database for future use. The reference measurement data can be stored, for example, in a memory of the ultrasonic measuring device. Alternatively, the reference measurement data can also be stored in a centralized server or cloud database. The calibration method of the present invention proposes to compare the initial reference measurement data generated by the manufacturer with the verification measurement data acquired by the operator. As will be explained in more detail below, the setting does not require the user to input the parameters of the reference object (e.g., calibration rod) into the measuring device. Instead, these parameters are only input by the manufacturer when determining the reference measurement data. On site, the operator uses the same measuring device to measure the same reference object. The processor (e.g., the processor of the ultrasonic measuring device) compares the verification measurement data so determined with the original reference measurement data to determine whether the size of the reference object is still measured with the same value (i.e., the same length). In one example, if the verification measurement is different from the reference measurement, the method may require adjusting the ultrasonic measuring device, that is, recalibrating the measuring device.

[0018] Before obtaining reference measurement data, it may be necessary to perform an initial calibration of the ultrasonic measuring device and / or the reference object prior to step a). The initial calibration is complex and is performed by experts in a laboratory. The initial measurement may include several measurements using one or more calibrated master scales and may require additional input of other parameters. The initial calibration performed by an expert ensures that subsequent calibrations are performed correctly. Since the initial calibration is performed by an expert, it is not considered a source of error.

[0019] According to another embodiment, the method includes assigning a reference ID to the reference object and assigning a device ID to the measuring device, and storing the reference measurement data in a database together with the corresponding reference ID and device ID, preferably in a memory of the measuring device. It should be understood that each reference object (e.g., each calibration rod) may have slightly different sizes. Similarly, each ultrasonic measuring device will return different ultrasonic lengths for the same reference object. Therefore, the reference measurement data is accurate only for a specific combination of a reference object and an ultrasonic measuring device. This embodiment suggests storing the identification of the reference object via the reference ID and the identification of the ultrasonic measuring device used to create the reference measurement data in a database together with the reference measurement data. In other words, the reference measurement data is marked with the reference ID of the reference object and the device ID of the ultrasonic measuring device used to create the reference measurement data. The database may include a plurality of different reference measurement data. One for each reference object. Therefore, the process may include retrieving the required measurement data based on the reference ID of the reference object and the device ID of the measuring device used by the operator on site.

[0020] In another embodiment, step e) comprises:

[0021] e1) determining the reference ID of the reference object;

[0022] e2) determining the device ID of the measuring device;

[0023] e3) Determine the reference length based on reference measurement data corresponding to the combination of the reference ID and the device ID.

[0024] The reference ID and the device ID may be marked on the corresponding object / device, be a serial number or a barcode / QR code. In other embodiments, the device ID of the measuring device may be stored in the memory of the measuring device. Similarly, the reference ID of the reference object may also be electronically accessed via the ultrasonic measuring device. Specifically, the ultrasonic measuring device may include a communication device for communicating with the reference object, i.e., communicating via an RFID tag mounted on the reference object. In this way, the ultrasonic measuring device may interrogate the reference object to determine the reference ID, which may then be provided to the processor of the measuring device. The processor of the measuring device may use the reference ID and the device ID so determined (which may be stored in the memory of the measuring device) to look up the corresponding reference measurement data corresponding to the combination of the reference ID and the device ID.

[0025] According to another embodiment, the method uses a single reference object for all verification measurements, regardless of the size of the bolted connection to be checked via the ultrasonic measuring device. The method of the invention does not require the use of a reference object of similar length to the bolt to be tested. Instead, a single reference object of any length can be used to perform verification measurements, regardless of the nominal length of the bolt to be checked.

[0026] According to another embodiment, measuring the reference object includes determining the flight time of the ultrasonic signal between a preset measurement origin and a point in time when the ultrasonic return signal is received. In this regard, it should be noted that the ultrasonic length of the object to be measured is not necessarily the time elapsed from the generation of the ultrasonic signal by the transducer to the reception of the return signal. Instead, a correction factor must be applied in order to take into account the time required for the ultrasonic signal to propagate from the transducer (e.g., via a coupling) into the material of the reference object. This time delay will be used to determine the measurement origin, i.e., typically a point in time shortly after the generation of the ultrasonic signal by the transducer.

[0027] According to another embodiment, adjusting the ultrasonic measurement device includes shifting the measurement origin based on the comparison result of the reference measurement data and the verification measurement data. In other words, any difference between the ultrasonic length determined based on the reference measurement data and the ultrasonic length determined based on the verification measurement data can be used to shift the measurement origin to recalibrate (adjust) the ultrasonic measurement device. The recalibration method is based on the concept that a specific pairing of an ultrasonic measurement device and a reference object should always return the same measurement data. The difference between the two is usually caused by wear of one or more components of the measurement device (such as a transducer) and can be compensated by shifting the measurement origin.

[0028] According to another embodiment, the measurement origin is shifted based on the length difference determined by multiplying the comparison result with a constant correction factor.The correction factor may be a function of the speed of sound in the material of the reference object.

[0029] According to another embodiment, comparing the length comprises determining a length difference between a length determined based on the reference measurement data and a length of the reference object determined based on the verification measurement data, wherein the method comprises comparing the length difference with a calibration threshold. In other words, the method may comprise a step of verifying whether recalibration is required. To this end, the method may recalibrate the measuring device only if a calibration threshold is exceeded.

[0030] The calibration threshold can be between ±0.00 mm and ±0.02 mm.

[0031] According to another embodiment, the method comprises repeating steps d) to f) until the length difference is below the calibration threshold. That is, if the calibration threshold is exceeded, the method comprises adjusting (recalibrating) the ultrasonic measuring device to compensate for the length difference between the reference measurement and the verification measurement. The method will then return to step d) and provide a verification measurement using the adjusted settings of the ultrasonic measuring device again. This new verification measurement data is then compared with the original reference measurement data to determine whether the difference between the reference measurement data and the verification measurement data is now below the calibration threshold. Once it is determined that the length difference is within the above-mentioned calibration threshold, a status signal can be provided to the user to inform them that the ultrasonic measuring device is now recalibrated and available for use. In some embodiments, the recalibration process can be recorded in a memory together with the device ID of the ultrasonic measuring device used.

[0032] In another embodiment, the reference measurement data includes any one or more of the following:

[0033] - the ultrasonic signal waveform determined during the reference measurement;

[0034] - the length of the reference object determined during the reference measurement;

[0035] - The time of flight of the ultrasonic signal during the reference measurement.

[0036] In another embodiment, the verification measurement data includes any one or more of the following:

[0037] - the ultrasonic signal waveform determined during the validation measurement;

[0038] - the length of the reference object determined during the verification measurement;

[0039] - The time of flight of the ultrasonic signal during the validation measurement.

[0040] In another embodiment, when a waveform of an ultrasonic signal is used, the method includes storing the reference measurement data together with the positive or negative polarization of the waveform used for calibration. Positive or negative polarization here refers to the positive part or negative part of the waveform. When compared with the verification measurement data, the polarization used for calibration can be shown in the background of the image to avoid polarity ambiguity. Polarity uncertainty means that if a calibration is measured using positive polarity and then a subsequent calibration is performed using negative polarity, the entire wave will be shifted by 1 / 2 wavelength, resulting in an erroneous elongation measurement result.

[0041] In another embodiment, the method includes recording the time when the ultrasonic measuring device was last verified and / or calibrated. This information can be recorded in a local or remote database along with the device ID and / or reference ID. In some embodiments, the timestamp can be used to remind the operator to regularly verify / recalibrate the ultrasonic measuring device. The reference ID can be used to see which reference objects were used in the most recent calibration and the number of times each reference object was used.

[0042] In another embodiment, the method includes recording the number of measurements since the last verification and / or calibration of the ultrasonic measuring device. The measurements here refer to all measurements other than reference measurements and / or verification measurements. This information can be recorded in a local or remote database together with the device ID. In some embodiments, this number can be used to remind the operator to regularly verify / recalibrate the ultrasonic measuring device. For example, the operator can be reminded to calibrate the ultrasonic measuring device after 100, 200, or 500 measurements.

[0043] According to another aspect of the present invention, there is provided an ultrasonic measuring device for determining the ultrasonic length of an object (preferably a bolt), the ultrasonic measuring device comprising:

[0044] - Ultrasonic transducer;

[0045] - Ultrasonic receiver;

[0046] - a memory for storing measurement data;

[0047] - a controller, the controller being configured to:

[0048] a) receiving reference measurement data representing an ultrasonic length of the reference object recorded during a first measurement of the reference object;

[0049] b) storing the reference measurement data in the memory;

[0050] c) receiving verification measurement data representing the ultrasonic length of the reference object recorded during a second later measurement of the reference object;

[0051] d) comparing a reference length of the reference object determined based on the reference measurement data with a verification length of the reference object determined based on the verification measurement data;

[0052] e) adjusting the ultrasonic measurement device based on the comparison result of the reference measurement data and the verification measurement data.

[0053] The invention will now be described in more detail with reference to exemplary embodiments shown in the accompanying drawings, in which:

[0054] Figure 1is a schematic representation of an ultrasonic measuring device connected to a bolt;

[0055] Figure 2 is a schematic view of a series of ultrasonic measurement devices and reference objects and corresponding databases;

[0056] Figure 3 is a schematic diagram of an ultrasonic signal that can be detected by an ultrasonic measuring device;

[0057] Figure 4 is a schematic diagram of comparing reference measurement data and verification measurement data according to the method;

[0058] Figure 5 is a schematic diagram showing the calibration of an ultrasonic measuring device;

[0059] Figure 6 is a schematic flow chart of a method for calibrating an ultrasonic measuring device according to an embodiment of the present invention.

[0060] Figure 1 1 is a schematic representation of an ultrasonic measuring device 100 for determining the length of a bolt 102. The ultrasonic measuring device includes a main unit 104 and a transducer 106. The transducer 106 is electrically connected to the main unit 104. The main unit 104 may include a memory, a processor, and a user interface, the user interface including a display 108 and / or a button 110. Of course, the interface may also be a touch screen interface, or a combination thereof.

[0061] Transducer 106 is coupled to bolt 102 via coupling 112. Coupling 112 facilitates propagation of the ultrasonic signal generated by transducer 106 into the material of bolt 102.

[0062] The main unit 104 activates the transducer 106 to generate an ultrasonic signal, which is transmitted into the bolt 102 via the coupling portion 112. Figure 1 In the example shown, the transducer 106 is a combined transducer / receiver configured to generate an ultrasonic signal and simultaneously receive a return signal. In this example, the return signal is a reflection of the ultrasonic signal generated by the transducer 106.

[0063] The ultrasonic signal (wave) is directed via transducer 106 along the longitudinal axis of bolt 102, i.e., in the direction of main propagation path 114. Once the ultrasonic wave reaches end face 116 of bolt 102, it is reflected back to transducer 106 along return path 118.

[0064] The ultrasonic measuring device 100 is configured to determine an ultrasonic signal at the start of the propagation path and a reflected ultrasonic signal received by the transducer 106. The ultrasonic measuring device 100 may show one or both signals on the display 108 to enable an operator to verify the quality of the measurement.

[0065] In some embodiments, the ultrasonic measuring device 100 may also be configured to determine the flight time of the ultrasonic signal within the bolt 102, i.e., the time between the generation of the ultrasonic signal and the reception of the return signal. As is well known in the art, the flight time is a measurement of the length of the bolt 102 in the longitudinal direction. Specifically, the flight time multiplied by the speed of sound within the bolt 102 can yield the length of the bolt 102.

[0066] Calculating the time of flight requires calibration of the ultrasonic measuring device 100. Specifically, the time of flight within the bolt 102 is slightly shorter than the duration between the generation of the ultrasonic signal by the transducer 106 and the receipt of the return signal by the corresponding sensor. The difference between the measured duration and the actual time of flight depends on various factors, which are generally well known in the art. To compensate for such environmental effects, each ultrasonic measuring device 100 is calibrated before being prepared for use.

[0067] In order to calibrate the ultrasonic measuring device 100, an object of known length, such as a calibration rod, is measured using the ultrasonic measuring device. In one example, the calibration rod may have an exact length of 150 mm. If during calibration, the ultrasonic measuring device determines that the length of the calibration rod is greater than or less than 150 mm, the time measurement of the ultrasonic measuring device 100 will be set to the measurement origin, thereby ensuring that the calculated length of the calibration rod is exactly 150 mm. It should be understood that the measurement origin of the ultrasonic measuring device 100 will typically be shifted to after the point in time when the transducer 106 generates the ultrasonic signal to compensate for the time required to propagate through the coupling portion 112.

[0068] Over time, the measurement results of the ultrasonic measuring device may deteriorate due to wear of one or more components of the ultrasonic measuring device. Therefore, it is necessary to recalibrate the ultrasonic measuring device regularly. The present invention provides a method for recalibrating an ultrasonic measuring device in a simple and effective manner. To this end, the present invention proposes to use a reference measurement of a reference object (e.g., a calibration rod) to determine whether the measuring device is still properly calibrated at a later point in time. In contrast, the method of the prior art proposes to recalibrate the measuring device 100 in the same way as the manufacturer did during the initial calibration described above. In contrast, the present invention proposes to recalibrate the ultrasonic measuring device only when there is a sufficiently large difference between the reference measurement (e.g., the initial calibration measurement) and the verification measurement performed by the operator. If it is determined that there is a difference, the ultrasonic measuring device can be adjusted based on the difference between the two measurement results (e.g., the two ultrasonic lengths measured during the reference measurement and the verification measurement).

[0069] Go to Figure 2 , a schematic representation of a set of reference objects (e.g., calibration rods) 200, 202, 204 and corresponding measuring devices 206, 208, 210 is shown. According to one aspect of the present disclosure, each reference object 200, 202, 204 is measured via each ultrasonic measuring device 206, 208, 210. The measurement results of each reference object 200, 202, 204 made by each ultrasonic measuring device 206, 208, 210 are stored in a database 212, which is also stored in a database 212. Figure 2 In this example, nine measurement results are input into the database 210. To this end, each reference object is marked with a reference ID, and each ultrasonic measuring device 206, 208, 210 is marked with a corresponding device ID. Figure 2 The exemplary database 210 of shows device IDs 1001, 1002, 1003 corresponding to three ultrasonic measurement devices 206, 208, 210. Reference objects 200, 202, 204 are represented in the database 210 as reference objects No. 1, No. 2, and No. 3. Of course, any type of device ID / reference ID may be used.

[0070] The representation of the database 210 also shows that the reference measurements of the first ultrasonic measuring device 206 (device ID 1001) for each of the three reference objects 200, 202, 204 are 1450 mm, 1452 mm, and 1449 mm, respectively. The remaining ultrasonic measuring devices 208, 210 measure the same reference objects 200, 202, 204, but with slightly different lengths, such as Figure 2 The data is obtained from the database 210 shown.

[0071] Therefore, in Figure 2In the above example, the reference measurement data representing the ultrasonic length of the reference object is the physical length of the reference object. However, it should be noted that the present application is not limited to reference measurement data including physical lengths. Instead, the reference measurement data stored in the database and linked to the corresponding ultrasonic measuring device and the reference object can be any other type of data representing the ultrasonic length of the reference object. In some embodiments, the reference measurement data can be a time-of-flight measurement result without being converted into a physical length by the speed of sound. In another embodiment, the reference measurement data can be in the form of an ultrasonic signal determined during the reference measurement, as will be described in more detail below. In the latter case, the reference measurement data is not a single parameter, but a wave function, which is stored in the database and linked to the corresponding measuring device and the reference object.

[0072] Figure 2 It is also shown that each reference object 200, 202, 204 and each ultrasonic measuring device 206, 208, 210 is equipped with an optical (bar code or QR code) or electronic (RFID code) tag that can be scanned by an operator before or after verifying the measurement to help retrieve the reference measurement data stored in the database 210 for comparison, as will be described in more detail below.

[0073] Still refer to Figure 2 In some examples, one ultrasonic measuring device (e.g., 206) may be considered the primary measuring device. In some embodiments, reference measurement data may be recorded only via the primary measuring device. Each subsequent verification measurement performed by other ultrasonic measuring devices (e.g., 208, 210) may result in a deviation from the primary measurement result, such as Figure 2 As shown in the exemplary database 210 of FIG. Therefore, it is necessary to calibrate the system according to the above correction factors.

[0074] Figure 3 A schematic representation of an ultrasonic signal recorded by an ultrasonic measuring device during a reference measurement or a verification measurement is shown. At the start of a measurement, the transducer of the ultrasonic measuring device generates an ultrasonic pulse 302 and sends it to a reference object. The ultrasonic pulse 302 is generated at a first point in time.

[0075] Figure 3 A second pulse 304 is shown, which has a waveform substantially the same as the first pulse 302. The second pulse 304 represents the return signal received by the sensor of the ultrasonic measuring device. During the process of the pulse wave propagating through the reference object, the amplitude of the ultrasonic signal decays. Therefore, the amplitude of the second pulse 304 of the return signal is lower than the amplitude of the initial pulse 302.

[0076] Figure 3Also schematically shown is a measured duration 306 during which the sensor receives no ultrasonic signal. It should be appreciated that this is a simplification of real world signals and that background noise will generally always be present. However, the duration 306 relates to the time when no significant ultrasonic signal is received.

[0077] Once the return signal is received, the ultrasonic measuring device can determine the flight time. The flight time determined by the ultrasonic measuring device can be the duration between "0" and the first corresponding peak of the pulse waveform 302, 304 or between two corresponding peaks. Figure 3 In the exemplary representation of , the flight time 308 is determined as the duration between the second positive half-waves of the corresponding pulses 302 , 304 .

[0078] As previously described, the reference measurement data and the validation measurement data may each include the time of flight 308, the length of the ultrasonic wave determined by multiplying the time of flight 308 by the speed of sound, and / or a representation of a waveform detected by the ultrasonic measurement device (e.g., Figure 3 300 in FIG.

[0079] The invention proposes to compare reference measurements and validation measurements performed on the same reference object at different points in time using the same or another ultrasonic measuring device. The reference measurement can be performed by the manufacturer, while the validation measurement can be performed by the operator before use and / or at predefined intervals. Based on possible differences between the reference and validation measurements, the ultrasonic measuring device can be adjusted / recalibrated to compensate for any measurement errors due to wear of the measuring device.

[0080] Figure 4 A schematic representation of the comparison between a reference measurement and a validation measurement is shown. Figure 4 In the embodiment of FIG. 4 , the figure shows two different return signals 402, 404. The first return signal 402, shown as a solid line, represents the ultrasonic length measured during the reference measurement. In other words, the return signal 402 is stored in the database as reference measurement data linked to a specific reference object and a specific measurement device (compare Figure 2 ). In other words, the return signal 402 is measured when the manufacturer initially calibrates the reference object. The corresponding return signal is then stored in, for example, database 212 and linked to the corresponding reference object (object ID) and measurement device (device ID).

[0081] The return signal 404 shown as a dashed line represents a verification measurement taken by an operator (e.g., in the field) at a later point in time. However, it should be noted that the second return signal 404 is determined for the same reference object as the first return signal 402. In some embodiments, the second return signal 404 is determined by the same ultrasonic measurement device as the first return signal 402. In alternative embodiments, the second return signal 404 is determined by a different ultrasonic measurement device than the first return signal 402. The second return signal 404 represents the verification measurement data obtained during the verification measurement.

[0082] Comparison of the two return signals 402, 404 shows the difference in ultrasonic lengths of the same reference object determined by the ultrasonic measuring device(s). Figure 4 In the example of , the second peak of the return signal 402 of the reference measurement data is, for example, located at a length of approximately 145 mm. In contrast, according to the verification measurement data, the second peak of the return signal 404 is located at approximately 146 mm. In other words, the difference in the measurement results of the reference object between the two return signals 402, 404 is approximately 1 mm. The processor can compare this difference 406 to a calibration threshold to determine whether the measurement device needs to be recalibrated. In some embodiments, the calibration threshold can be 0.02 mm. Applied to Figure 4 In the example of , the processor will determine that recalibration is needed because the difference 406 exceeds the calibration threshold. Of course, it should be understood that the calibration threshold can be adjusted to any suitable value.

[0083] Verification measurements may be performed periodically. For example, the processor may prompt the operator to initiate verification measurements periodically (i.e., after a predetermined amount of time after the last calibration). In this way, it may be ensured that the measuring device is properly calibrated periodically. Alternatively, the operator may perform a verification measurement each time the length of the bolted joint is determined using the ultrasonic measuring device. The verification measurement itself is not a recalibration of the ultrasonic measuring device. Rather, the verification measurement is used to ensure that the ultrasonic measuring device is still properly calibrated and thus returns correct measurements, i.e., within acceptable tolerances.

[0084] It should also be noted that the reference measurement data and verification measurement data of the present invention are not limited to Figure 4 The waveforms of the return signals 402 and 404 are shown. As described above, any type of data representing the ultrasonic length of the reference object can be used as part of the reference measurement data and the verification measurement data, respectively. For example, the reference measurement data and the verification measurement data can include a time-of-flight measurement and / or an ultrasonic length determined based on such a time-of-flight measurement.

[0085] If the processor determines that the ultrasonic measuring device needs to be recalibrated, the processor can notify the operator. The operator can then decide to manually initiate the recalibration. Alternatively, if the processor determines that recalibration is required, it can automatically recalibrate the measuring device.

[0086] If the processor determines that the ultrasonic measurement device needs to be recalibrated based on the comparison between the reference measurement data and the validation measurement data, the processor may adjust the ultrasonic measurement device based on the difference 406 between the reference measurement and the validation measurement.

[0087] It should be noted that when performing subsequent measurements / validation measurements, it is not the raw ultrasonic data that is compared to the reference measurement data. This also includes temperature compensation and potential stress factors that depend on the nature of the material the reference rod is made of.

[0088] Figure 5 An example of adjusting the measurement device based on a previously determined difference 406 is shown. Specifically, Figure 5 The adjustment shown involves a shift in the measurement origin of the ultrasonic measuring device. As previously mentioned, during the initial calibration of the ultrasonic measuring device, a preset measurement origin is determined. This preset measurement origin is determined by the manufacturer of the ultrasonic measuring device and is Figure 5 502. A function 504 extending from the preset measurement origin 502 represents the relationship between the flight time of the ultrasonic signal in the bolt to be measured and the corresponding ultrasonic length. As is well known in the art, the ultrasonic length is proportional to the flight time, and the slope of the function 504 depends on the speed of sound in the object to be measured. Another calibration procedure can be used to verify / calibrate the characteristics of the function 504 every year. However, for simplicity, in the present disclosure, it is assumed to be a constant.

[0089] A scenario can be considered in which the origin 502 and the function 504 are preset with Figure 4 The ultrasonic measuring device shown is used for reference and verification measurements. Figure 4 In the measurement results shown, the difference between the reference measurement and the verification measurement exceeds the calibration threshold, so the measurement device should be recalibrated (i.e., adjusted) to compensate for the difference between the reference measurement data and the verification measurement data. For example, during the verification measurement, the ultrasonic measurement device determines the flight time of the ultrasonic signal in the reference object to be t1. Using the preset measurement origin 502, such a flight time t1 will correspond to the ultrasonic length L1 of the reference object. However, from Figure 4 It can be concluded that the ultrasonic length L1 is not accurate because it is different from the ultrasonic length determined during the reference measurement. Figure 4 In the example of , the ultrasonic length L1 of the verification measurement is 1 mm longer than the ultrasonic length determined based on the reference measurement. Figure 5The adjustment of the ultrasonic measuring device is shown to compensate for this scenario (the measured ultrasonic length is too large). In this scenario, the preset measurement origin 502 of the ultrasonic measuring device is shifted in the positive direction along the flight time axis. The preset measurement origin 502 can be shifted by a time shift T2. Figure 5 The new measurement origin is shown with reference numeral 508 in FIG. 1 . The corresponding dashed line shows a function 510 between the flight time and the length. Function 510 is shown with a dashed line and is parallel to function 504 before recalibration / adjustment of the ultrasonic measuring device. As previously described, the slope of function 510 does not change compared to function 504 because the speed of sound within the reference object is constant. Due to the time shift T2, the flight time t1 measured by the ultrasonic measuring device now corresponds to an ultrasonic length L2, which is lower than the ultrasonic length L1 measured before the adjustment / recalibration. In one example, the difference 512 between the ultrasonic length L1 before recalibration and the ultrasonic length L2 after recalibration is equal to Figure 4 The length difference 406 determined during the verification step is shown. To this end, the processor may be configured to multiply the length difference 406 determined during the verification by a constant factor to determine the time shift T2. In some embodiments, the correction factor may represent the speed of sound within the reference object.

[0090] It should be understood that Figure 5 Adjustment of the measurement origin shown in FIG. 5 between origins 502 and 508 will result in Figure 4 The waveform of the return signal 404 of the verification measurement in is shifted to the left, so that Figure 4 The return signals 402, 404 are substantially identical to each other.

[0091] Once recalibration is complete (i.e., the measurement origin is appropriately shifted), another verification measurement can be taken automatically or triggered by the operator. The processor can compare the new verification measurement results with the reference measurement data to determine Figure 4 The processor may determine whether the differences shown in have been compensated, or whether any potential remaining differences are below the calibration threshold. If the difference between the reference measurement data and the calibrated new verification measurement data is below the calibration threshold, the recalibration process is complete and the processor may record the date and / or time of the recalibration. Conversely, if the difference between the reference measurement data and the new verification measurement data still exceeds the calibration threshold, the processor may adjust / recalibrate the ultrasonic measurement device again. The processor may repeat this process until the verification measurement data no longer differs significantly from the original reference measurement data.

[0092] Go to Figure 6, shows a schematic flow chart of a method for recalibrating an ultrasonic measuring device. The method 600 starts with step S602, where a verification measurement process is started. For example, the operator may choose to verify the calibration of the ultrasonic measuring device before starting any measurement of the bolted joint. Alternatively, the ultrasonic measuring device may prompt the operator to start a verification measurement at fixed time intervals, for example, based on the time elapsed since the last verification measurement. To this end, the processor may use a reference Figure 5 Timestamp after the mentioned recalibration.

[0093] In a second step S604, a reference object ID of a reference object for verification measurement is determined. It should be understood that there may be many ways to determine the reference object ID. Some examples include a barcode, a QR code, an RFID tag, or an ID simply printed on the reference object. The ultrasonic measurement device (i.e., the processor) may prompt the user to provide the reference ID of the reference object. To this end, the user may scan the corresponding barcode or QR code via the ultrasonic measurement device. Alternatively, the ultrasonic measurement device may automatically communicate with the reference object, for example via an RFID tag, so as to automatically determine the reference object ID after the verification process is started.

[0094] In a second step S606, the measuring device ID is determined. Similar to the determination of the reference object ID, the device ID of the ultrasonic measuring device may be scanned or input by a user, or automatically determined by a processor. As described above, the measuring device ID may be stored in a memory of the ultrasonic measuring device, so that the processor may look up the measuring device ID at any time. It should be understood that step S604 and step S606 may be performed in any order or simultaneously.

[0095] In another step S608, the processor will obtain the reference measurement data stored during the original calibration of the ultrasonic measurement device. The reference measurement data can be stored in a local or remote database and linked to the specific reference object and measurement device used during the original calibration. Therefore, the processor can retrieve the reference measurement data from the database by looking up the object ID and device ID determined in steps S604, S606.

[0096] In another step S610, the user positions the sensor and starts the verification measurement. In some embodiments, once the reference object ID and the measurement device ID are determined, the processor of the ultrasonic measurement device can prompt the user to position the sensor. The ultrasonic measurement device can guide the user to correctly position the sensor on the reference object to be measured during the verification measurement. Once the sensor has been positioned, the user can trigger the verification measurement, for example by pressing a corresponding button on the ultrasonic measurement device.

[0097] The ultrasonic measuring device will then continue to perform ultrasonic length measurements on the reference object to obtain verification measurement data, which can be compared with the stored reference measurement data in step S612. If during step S612, the comparison between the verification measurement data and the reference measurement data (see Figure 4 ) indicates that the ultrasonic length determined based on the verification measurement data is within the calibration tolerance of the ultrasonic length based on the reference measurement data, the processor will determine that recalibration is not required and notify the user that the ultrasonic measurement device has been accurately calibrated.

[0098] However, if the verification measurement is not within the calibration tolerance during step S612, the processor will automatically initiate a recalibration step S614 or notify the user that recalibration appears to be required. The user can then manually activate the recalibration step S614. Once the recalibration step S614 is initiated, the processor can adjust the ultrasonic measurement device to compensate for the difference between the reference measurement and the verification measurement (see, e.g., above). Figure 5 ).

[0099] Once the recalibration step S614 is completed, the processor can again perform the verification measurement (the ultrasonic transducer / sensor should still be in place) and determine whether the verification measurement is now within tolerance. If the difference has been corrected by the recalibration step S614, the processor can again notify the user that the ultrasonic measurement device is now properly calibrated and can be used for the measurement of bolted joints.

[0100] In optional step S616, the processor may record the verification process and, where appropriate, the recalibration process with a timestamp, so that an operator or manufacturer can query at any time when the calibration of the ultrasonic measuring device was last verified / when it was last recalibrated.

Claims

1. A method for calibrating an ultrasonic measuring device, in particular an ultrasonic bolt testing device, the method comprising the following steps: a) Provide reference objects; b) measuring the reference object via an ultrasonic measuring device to determine reference measurement data representing an ultrasonic length of the reference object; c) storing the reference measurement data; d) measuring the reference object using the same or another ultrasonic measuring device to determine verification measurement data representing the ultrasonic length of the reference object; e) comparing a reference length of the reference object determined based on the reference measurement data with a verification length of the reference object determined based on the verification measurement data; f) adjusting the ultrasonic measurement device based on the comparison of the reference measurement data with the validation measurement data.

2. The method according to claim 1, It comprises assigning a reference ID to the reference object and a device ID to the measuring device, and storing the reference measurement data together with the corresponding reference ID and device ID in a database, preferably in a memory of the measuring device.

3. The method according to claim 1 or 2, in, Step e) comprises: e1) determining a reference ID of the reference object; e2) determining the device ID of the measuring device; e3) determining the reference length based on reference measurement data corresponding to a combination of a reference ID and a device ID.

4. The method according to any one of claims 1 to 3, in, A single reference object is used for all verification measurements, regardless of the size of the bolted joint to be checked via the ultrasonic measuring device.

5. The method according to any one of claims 1 to 4, in, Measuring the reference object includes determining a flight time of the ultrasonic signal between a preset measurement origin and a time point at which an ultrasonic return signal is received.

6. The method according to claim 5, in, Adjusting the ultrasonic measurement device includes shifting the measurement origin based on a comparison result of the reference measurement data and the verification measurement data.

7. The method according to claim 6, in, The measurement origin is shifted according to the length difference determined based on the comparison result multiplied by a constant correction factor.

8. The method according to any one of claims 1 to 7, in, comparing the length comprises determining a length difference between a length determined based on the reference measurement data and a length of the reference object determined based on the verification measurement data, Therein, the method includes comparing the length difference with a calibration threshold.

9. The method according to claim 8, The ultrasonic device is adjusted only when the length difference exceeds the calibration threshold.

10. The method according to claim 8 or 9, Comprising repeating steps d) to f) until the length difference is below the calibration threshold.

11. The method according to any one of claims 8 to 10, in, The calibration threshold is between ±0.00 mm and ±0.02 mm.

12. The method according to any one of claims 1 to 11, wherein: The reference measurement data includes any one or more of the following: - an ultrasonic signal waveform determined during said reference measurement; - the length of said reference object determined during said reference measurement; - The time of flight of said ultrasonic signal during said reference measurement.

13. The method according to any one of claims 1 to 12, wherein: The verification measurement data includes any one or more of the following: - the ultrasonic signal waveform determined during said validation measurement; - the length of said reference object determined during said verification measurement; - The time of flight of said ultrasonic signal during said validation measurement.

14. The method according to any one of claims 1 to 13, including a record of the last time the ultrasonic measuring device was verified and / or calibrated, and / or This includes recording the number of measurements taken since the last verification and / or calibration of the ultrasonic measurement device.

15. An ultrasonic measuring device for determining the ultrasonic length of an object, preferably a bolt, the ultrasonic measuring device comprising: - Ultrasonic transducer; - Ultrasonic receiver; - a memory for storing measurement data; - a controller, the controller being configured to: a) receiving reference measurement data representing an ultrasonic length of the reference object recorded during a first measurement of the reference object; b) storing the reference measurement data in the memory; c) receiving verification measurement data representing the ultrasonic length of the reference object recorded during a second later measurement of the reference object; d) comparing a reference length of the reference object determined based on the reference measurement data with a verification length of the reference object determined based on the verification measurement data; e) adjusting the ultrasonic measurement device based on a comparison of the reference measurement data with the validation measurement data.

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