METHOD, SYSTEM AND TOOL FOR DETERMINING A WALL THICKNESS OF AN OBJECT

Abstract

Method and system for determining a wall thickness of an object such as a pipeline using ultrasound. A pig is used comprising at least one first ultrasonic transducer which is attached to the pig for transmitting ultrasound in the object. Using at least one second ultrasonic transducer, a receiving signal is generated representing reflections of the ultrasound on the object received by the at least one second transducer. The received signals are processed employing a processor provided at the pig to obtain a compressed receiving signal. In use, the processor determines in the signal maximal N peaks having the largest amplitudes and associated information on the moment on which these peaks occur within the receiving signal. Information about the maximal N peaks and associated information on the moment on which these peaks occur is stored in a storing device of the pig.

Claims

1. A method for determining a wall thickness by use of ultrasound by a pig wherein the ultrasound is transmitted by at least one first ultrasonic transducer attached to the pig, wherein the ultrasound is transmitted in an object wherefrom the wall thickness has to be determined, wherein by use of at least one second ultrasonic transducer, a receiving signal is generated representing reflections of the ultrasound on the object received by the at least one second transducer, wherein the received signals are processed by a processor provided at the pig to obtain a compressed receiving signal, wherein the compressed receiving signal is stored in a storing device provided at the pig, wherein, in use, the processor determines in the receiving signal a maximal N peaks having largest amplitudes and associated information on a moment on which each one of the maximal N peaks occurs within the receiving signal, and wherein information about the maximal N peaks and associated information on the moment on which each one of the maximal N peaks occur is stored in the storing device.

2. The method according to claim 1, wherein peaks having positive and negative amplitudes are taken into account for determining the maximal N peaks in the compressed receiving signal.

3. The method according to claim 1, wherein N is in the range from 10 to 100.

4. The method according to wherein N is one of the group consisting of: 16, 32, 64, and 128.

5. The method according to claim 1, wherein the maximal N peaks are stored if the amplitude of each of the N largest peaks is larger than a first threshold value and wherein M<N peaks are stored if the signal only comprises M largest peaks having an amplitude which is larger than the first threshold.

6. The method according to claim 1, wherein more than one peak per interface is stored.

7. The method according to claim 1, wherein the first ultrasonic transducer and the second ultrasonic transducer are the same.

8. The method according to claim 1, wherein the pig comprises a plurality of the first and/or the second transducers.

9. The method according to claim 1, wherein the pig is moved axially inside a pipe filled with a fluid for measuring the wall thickness along the pipe circumference over a first length of the pipe, wherein the measured wall thickness is the wail thickness of the pipe, and wherein a plurality of measurements are carried out within the first length of the pipe.

10. The method according to claim 1, wherein an automatic event-picking is performed on the compressed receiving signal to determine time positions of different signals (echo's) of object wall interfaces, i.e. inner diameter and outer diameter.

11. The method according to claim 10, wherein the automatic event-picking comprises: picking of a stand-off (SO), wherein an event is searched which corresponds to the nearest wall; and determining an event center of remaining events; and picking of a wall thickness (WT).

12. The method according to claim 11, wherein a pre-processing of a compressed receiving signal is performed prior to the picking of the stand-off (SO).

13. The method according to claim 12, wherein during the pre-processing, the selected peaks of the compressed receiving signal are ordered in a time of flight index sequence.

14. The method according claim 12, wherein during the pre-processing, the peaks are grouped in an event group, wherein the peaks are grouped belonging to a same event group when consecutive indices of the index sequence are located close to each other.

15. The method according to claim 14, wherein the peaks are grouped belonging to a same event group when consecutive indices of the index sequence are separated by less than approximately three quarter of a wavelength.

16. The method according to claim 11, wherein the picking of the stand-off includes at least one of the group consisting of: determining a candidate SO event as the event having the peak with the highest amplitude in the compressed receiving signal, and selecting the candidate SO event as the SO event if the peak with the highest amplitude belongs to the first event group; and selecting an earlier event with the maximum amplitude before the candidate SO event as the SO event if it has an amplitude of more than 30%-50% of the candidate SO event amplitude and if the distance between the candidate SO event and the earlier event is approximately equal to the neighboring WT.

17. The method according to claim 16, wherein picking of the stand-off further includes determining a precise SO based on a weighted average of the indices of the SO pulse, wherein a weight is based on an absolute value of an amplitude.

18. The method according to claim 11, wherein determining an event center of remaining events includes using the shape of the determined SO pulse and apply a correlation function between event and determined SO pulse.

19. The method according to claim 11, wherein determining an event center of remaining events includes: eliminating one or more events for further analysis; calculating for the remaining events a cross correlation between the remaining event and the SO event; and determining a precise event center of the event.

20. The method according to claim 19, wherein the cross correlation is a negative correlation.

21. The method according to claim 20, wherein eliminating events for further processing comprises omitting peaks belonging to one or more events before the SO event, and omitting peaks belonging to one or more events for which at least one peak is beyond P times the SO event.

22. The method according to claim 21, wherein P is in the range between 1.5 to 2.

23. The method according to claim 1, wherein a wall thickness is determined using a plurality of events.

24. The method according to claim 23, wherein determining the WT includes: preprocessing the event centers, wherein the preprocessing the event centers includes: calculating the event centers of the WT reflections with respect to the SO event center, dismissing all events with an event center smaller than a threshold value so as to eliminate separate events in a tail of the SO event; and calculating the wall thickness of the object by determining the distance between SO and WT.

25. The method according to claim 1, wherein a plurality of WT events are used for calculating the wall thickness, wherein outliers are dismissed.

26. The method according to claim 1, wherein the pig comprises a processing unit arranged for performing automatic event-picking.

27. The method according to claim 1, wherein information about the stored peaks and associated information on the moment on which these peaks occur are transferred to a storage location accessible by a computer, wherein automatic event-picking is performed off line by the computer which is separated from the pig.

28. The method according to claim 1, wherein compression of the receiving signal and storage thereof is performed while one or more ultrasonic measurements are performed.

29. The method according to claim 1, wherein the compressed receiving signal is displayed in at least one of an A-scan display or a B-scan display.

30. The method according to claim 29, wherein the compressed receiving signal is processed prior to displaying.

31. The method according to claim 30, wherein the compressed receiving signal is at least rectified during processing prior to displaying.

32. The method to according to claim 10, wherein events picked by automatic event picking are marked in at least one of an A-scan or B-scan display of the compressed receiving signal.

33. The method according to claim 1, wherein N is a predetermined number.

34. The method according to claim 2, wherein peaks having positive and negative amplitudes are taken into account per event for determining the maximal N peaks in the compressed receiving signal.

35. The method according to claim 10, wherein an event is the at least one reflection (echo) of the ultrasound transmitted in the object wherefrom the wall thickness has to be determined, such as a reflection on an inner diameter (ID; inner surface) of the object or a reflection on an outer diameter (OD; outer surface) of the object.

36. A system for determining a wall thickness by ultrasound, the system comprising a pig comprising at least one first ultrasonic transducer attached to the pig arranged for transmitting an ultrasound in an object wherefrom the wall thickness has to be determined, at least one second ultrasonic transducer arranged for generating a receiving signal representing reflections of the ultrasound on the object received by the at least one second transducer, and a processor arranged for processing signals so as to obtain a compressed receiving signal, wherein the pig is arranged for storing the compressed receiving signal in a storing device provided at the pig, wherein, in use, the processor is arranged for determining in the signal maximal N peaks having the largest amplitudes and associated information on the moment on which these peaks occur within the receiving signal and wherein the pig is arranged for storing information about the maximal N peaks and associated information on the moment on which these peaks occur in the storing device.

37. The system according to claim 36, further comprising a computer, wherein the pig is arranged to be communicatively connected with the computer for transferring the compressed receiving signal, wherein the computer is arranged for performing automatic event-picking.

38. A non-transitory computer-readable medium comprising computer-executable instructions for facilitating determining a wall thickness by analyzing ultrasound echo signals obtained by a pig, wherein the computer-executable instructions, when executed by a processor, causing performing a method comprising: sending a signal for transmitting by at least one first ultrasonic transducer which is attached to the pig ultrasound in an object wherefrom the wall thickness has to be determined; sending a signal for generating by at least one second ultrasonic transducer a receiving signal representing reflections of the ultrasound on the object received by the at least one second transducer; sending a signal for processing the received signals by the processor provided at the pig so as to obtain a compressed receiving signal; sending a signal for storing the compressed receiving signal in a storing device provided at the pig; sending a signal for determining by the processor in the signal maximal N peaks having the largest amplitude and associated information on the moment on which these peaks occur within the receiving signal; and sending a signal for storing information about the maximal N peaks and associated information on the moment on which these peaks occur is stored in the storing device.

39. A pig comprising an ultrasound sensor, non-transitory computer-readable medium, and a processor, wherein the pig is configured to obtain ultrasound signals, and the processor is configured to execute instructions stored on the non-transitory computer-readable medium to carry out a method comprising: sending a signal for transmitting by at least one first ultrasonic transducer which is attached to the pig ultrasound in an object wherefrom the wall thickness has to be determined; sending a signal for generating by at least one second ultrasonic transducer a receiving signal representing reflections of the ultrasound on the object received by the at least one second transducer; sending a signal for processing the received signals by the processor provided at the pig so as to obtain a compressed receiving signal; sending a signal for storing the compressed receiving signal in a storing device provided at the pig; sending a signal for determining by the processor in the signal maximal N peaks having the largest amplitude and associated information on the moment on which these peaks occur within the receiving signal; and sending a signal for storing information about the maximal N peaks and associated information on the moment on which these peaks occur is stored in the storing device.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0070] The invention will further be elucidated on the basis of exemplary embodiments which are represented in a drawing. The exemplary embodiments are given by way of non-limitative illustration. It is noted that the figures are only schematic representations of embodiments of the invention that are given by way of non-limiting example.

In the Drawing

[0071] FIG. 1 shows an example of an ultrasound wall thickness measurement;

[0072] FIG. 2 shows compression of a receiving signal;

[0073] FIG. 3 shows event-picking in a compressed receiving signal; and

[0074] FIG. 4 shows a B-scan display.

DETAILED DESCRIPTION

[0075] FIG. 1 shows a simplified schematic representation of a wall thickness d.sub.wall measurement using ultrasound. An A-scan 1 is shown at the bottom of FIG. 1. The A-scan 1 gives a time signal of an ultrasonic measurement, showing a signal amplitude (vertical axis) in function of time (horizontal axis). The ultrasound 2 emitted by the transducer 3 will encounter an inner diameter (ID) of the pipe 4 and be reflected back towards the transducer 3, indicating an inside surface of the pipe 4. A part of the ultrasound will reach an outer diameter (OD) of the pipe 4 and be reflected back towards the transducer 3, indicating the outside surface of the pipe 4. The distance between the probe 4 and the first interface (fluid-pipe wall) is called a stand-off (SO). A plurality of OD echoes can be available at substantially equal distances from each other, depending on the situation. An interface echo typically has multiple peaks of different amplitudes, wherein the pattern substantially corresponds to the transmitted pulse. In this embodiment, the first transducer 3 and the second transducer 3 are the same. However, it is also possible to use a plurality of transducers 3. The receiving signal obtained by means of the transducer 3 comprises a send pulse 6, an ID echo 8a and an OD echo 8b. Thus it follows that an ID echo 8a and an OD echo 8b are events.

[0076] The ID echo 8a and OD echo 8b have a time gap of T therebetween. The ultrasonic transducer can be arranged on a pig. The pig can be used so as to determine the wall thickness by means of ultrasound. The receiving signal generated by the transducer 3 represents reflections of the ultrasound on the object or pipeline 4.

[0077] The received signals 1 are processed by means of a processor provided at the pig to obtain a compressed receiving signal, wherein the compressed receiving signal is stored in a storing device provided at the pig. The processor determines in the signal maximal N peaks having the largest amplitudes and associated information on the moment on which these peaks occur within the receiving signal and wherein information about the maximal N peaks and associated information on the moment on which these peaks occur is stored in the storing device. Thus it follows that N is a predetermined number.

[0078] When the compressed receiving signals for one or more measurements are stored on the pig, this information can be transferred to a computer for analyzing the compressed receiving signals offline by performing event picking.

[0079] The event picking can be carried out automatically. In an example, the automatic event picking is carried out by electronics arranged in the pig itself, or online through a communication connection to a computer. In such cases, advantageously, the file size of the receiving signal can be reduced while keeping relevant information required for accurate event picking.

[0080] FIG. 2 shows data compression of an original A-scan 1 (receiving signal) to a compressed A-scan 10 (compressed receiving signal). The ultrasonic receiving signal 1 is digitized at a sampling frequency that is sufficiently high so as to avoid discarding relevant information (cf. Nyquist theorem). In this example, the receiving signals of 5 MHz transducers are sampled at a sampling frequency of 50 MHz, resulting in approximately 10 measured points per sine-shaped wave (including one period with a positive and negative portion). FIG. 2a shows the plot of the original A-scan 1 sampled at a frequency of 50 MHz. A compression is obtained by converting the original A-scan 1 to a reduced data set with maximum N peaks, i.e. compressed A-scan 10. The receiving signal 1 shown in FIG. 2a comprises two distinct events 12 and 14. Only for a limited number of peaks 16, 18 that correspond to the local extremes, the amplitude is stored, as can be seen in FIG. 2b. In this process, both positive maximum or negative minimum values are taken into account. A rectification of the peaks is therefore not required. In the shown embodiment, a maximum of 32 positions are selected (i.e. N is equal to 32). This results in a limited number of position-amplitude or index-amplitude pairs, namely 32 or less peaks. The obtained compressed receiving signal 10 comprises two distinct events 16, 18 each comprising a plurality of positive and negative peaks or index-amplitude pairs. Optionally, noise can be reduced by discarding values lower than a noise threshold. The reduced data set of the compressed receiving signal 10 comprises all the relevant information. Optionally, from the compressed A-scan 10 or compressed receiving signal 10, a time signal can be reconstructed, especially if the main frequency of the original A-scan 1 is known. Then, the reconstructed signal can be evaluated just like an original A-scan (time) signal. However, according to the method, a reconstruction is not needed since the compressed receiving signal 10 comprises all the relevant information and can be used directly for evaluation and event-picking.

[0081] The data compression and data storage can be performed while the ultrasonic measurements are performed, so that the measurements process is not delayed or at least the delay can be reduced. In an embodiment, a plurality of ultrasonic transducers (e.g. 160 5 MHz probes) is used for covering a complete circumference of the investigated pipeline from the inside. Higher or lower number of ultrasonic transducers can be employed depending on the requirements of the set-up, characteristics of the used pig, the quality of the measurements, the size of the pipe, etc. A measurement can be performed for each transducer for every axial movement (e.g. every 5 mm) of the pig, while the pig is moved at a speed within the pipe (e.g. 0.5 meter per second). Other axial movement and speeds can also be used.

[0082] In the shown embodiment, the A-scan is performed with digitization at 50 MHz. Compression of the receiving signal 1 or A-scan 1 is performed using the highest N peaks in the signal, e.g. using a three-point local extreme or maximum values between zero-crossings method. Other methods can be employed. In this example N is equal to 32 but other N values can also be used. The compressed receiving signal 10 (i.e. compressed A-scan 10) linked to the coordinates of the measurement position is then stored. This can be followed by an evaluation such as an event-picking, which can be performed online or offline. Combinations are also envisaged, wherein a part of the evaluation is performed online and a part offline. Furthermore, the pig may comprise means for performing the evaluation by itself, without the need of an external device such as a computer.

[0083] In case of offline evaluation, the compressed A-scans are transferred from the pig to a computer. The compressed A-scans can then be processed into the stand-off (SO) distance, stand-off amplitude and a wall thickness distance, using an automatic event-picker. Other features can also be processed, such as for example the amplitude of wall thickness. Reconstruction and/or decompression is not required and therefore not performed. The automatic event-picker employs a correlation function for finding a position of an event, wherein the position of the event does not necessarily have to coincide with one of the positions in the compressed receiving signal. For finding the position of the ID event in the ID echo a weighted average of the indices of the SO pulse is used, wherein a weight is based on an absolute value of an amplitude. The ID echo signal can be used for finding the positions of the OD events by applying a correlation. For the OD echoes a negative correlation is used because the OD echoes have a phase opposite to the ID echo. The automatic event-picking can be configured for taking multiples of the wall thickness into account, if available and usable. The outcome of an automatic event-picking can be visualized in known ways such as displays showing a color map of SO and WT.

[0084] In case of disturbed, weak or missing signals the results of adjacent pixels may be taken into account during the automatic event-picking. The selected position of SO and WT can then be verified by the operator in the display of the compressed A-scan.

[0085] Additionally or alternatively, events in the compressed receiving signal or compressed A-scan can be picked by an operator such as an ultrasonist, instead of using a complete receiving signal or A-scan.

[0086] FIG. 3 shows different events which are visualized in the compressed receiving signal. The compressed receiving signal or compressed A-scan provides compressed ultrasonic time signals. The at least one first and second transducers may be arranged on a pig, wherein the first and second transducers may be the same. The information received by the at least one second transducer, i.e. the receiving signal, can be compressed and stored as the compressed receiving signal in the pig, wherein the compression of the receiving signal is obtained by selecting for each A-scan a maximum predetermined number of peaks, which peaks may be positive and negative, and storing said peaks on the pig. The predetermined number of peaks can for example be 16, 32, 64. Other numbers are also possible. In this example a maximum number of 32 peaks are chosen from the receiving signal so as to obtain the compressed receiving signal. Further, the selected peaks in the compressed receiving signal are only selected when the peaks exceed a certain threshold value. Other criteria can also be employed so as to improve the quality of the compression of the receiving signal.

[0087] The compressed receiving signal is collected by the pig and stored therein, wherein an A-scan compression is carried out such as to obtain a compressed receiving signal. The information can then be read out and subsequently analyzed by an automatic event picker for performing automatic event picking.

[0088] The horizontal axis of the plot in FIG. 3 indicates time T (e.g. time index multiplied by sample frequency) and vertical axis indicates amplitude A. A distance on the horizontal axis can be used to calculate a distance, by multiplication with the sound speed. Multiple back wall reflections are used for determining the wall thickness in the compressed receiving signal. The peaks are grouped. The echoes in the compressed receiving signal are marked by the automatic event-picker, including an ID echo position 50a, first OD echo position 52a, multiple OD echoes 54a and 56a, each marked with a dashed line, respectively, line 50, line 52, line 54, line 56. Line 50 marks the SO and line 52 marks the WT. Thus it follows that the positions of the events are marked with a (dashed) line. From the distance 60 between line 50 and line 52, the wall thickness can be determined. The compressed receiving signal comprises a total of 24 peaks, with N=32. The SO is formed by the first group comprising a plurality of peaks 100. The SO signal and the WT signal typically have opposite phase with respect to each other.

[0089] Each peak or index-amplitude pair of the compressed A-scan is visualized separately, wherein the amplitude is indicated by a point. The index-amplitude pairs in a same event can be grouped (e.g. also displayed with a same color), such as to be able to easily distinguish different events from each other. The WT and WT multiples are indicated taking into account that a WT position corresponds to SO+n.Math.WT, wherein n is a positive integer number.

[0090] Advantageously, an operator can quickly visually check the performance of the automatic event-picking, i.e. check whether the lines indicating stand-off and wall thickness are positioned at event groups and no signals are missed by the automatic event-picker. In an example, different settings or algorithms for the automatic event-picker can be tested and optimized, if necessary.

[0091] An advantage of the compression is that on the basis of an image, in the form of an amplitude-time diagram, of the amplitudes stored in the pig and supplemented with generated events by the automatic event picker, an expert such as an ultrasonist can visually judge the quality of the results of the automatic event picker. Additionally, the ultrasonist can perform the event picking himself on the basis of an image of the stored amplitudes in the amplitude-time diagram.

[0092] Advantageously, a measurement result can be used to improve the evaluation of adjacent measurements.

[0093] Furthermore, additionally, the ID position can be used to determine a correction in case the pig was positioned off-center relative to the pipe cross-section.

[0094] The visualization illustrated in FIG. 3 shows a compressed receiving signal 10 containing all relevant information. Therefore, this data can be used for constructing other displays. This may be displays which are used for conventional A-scan data, for example a B-scan display or C-scan display. For example, the compressed data can be rectified and an envelope can be constructed for the data to be displayed in B-scan.

[0095] FIG. 4 shows a B-scan display, wherein the horizontal axis represents a position x in an axial or a circumferential direction, and vertical axis represents time T (with a positive direction from top to bottom). A plurality of lines relating to the ID, WT and WT multiples is shown in the B-scan display. The intensity of the plotted lines is representative for the amplitude. Optionally, events found by the event picker can be marked by lines or dots in the B-scan display, which may support an ultrasonist in verification of the results obtained by automatic event picking in a fast and user friendly manner. For example, the selected events can be displayed in a C-scan display showing a mapping of the pipe wall in both axial and circumferential direction with a color or intensity to represent the measured value of SO or WT. Typically an indicator such as a cross hair cursor is used in the C-scan display to indicate the selected measurement position for which the data is also shown in A-scan or B-scan. In an example, the various displays are shown together to present the ultrasonist with an overview and to compare the various displays. In this way, measurement results at adjacent positions can be easily compared.

[0096] It will be appreciated that the method may include computer implemented steps. The invention also extends to computer programs, particularly computer programs on or in a carrier, adapted for putting the invention into practice. The program may be in the form of source or object code or in any other form suitable for use in the implementation of the processes according to the invention. The carrier may be any entity or device capable of carrying the program. For example, the carrier may comprise a storage medium, such as a ROM, for example a CD ROM or a semiconductor ROM, or a magnetic recording medium, for example a floppy disc or hard disk. Further, the carrier may be a transmissible carrier such as an electrical or optical signal which may be conveyed via electrical or optical cable or by radio or other means, e.g. via the internet or cloud.

[0097] Some embodiments may be implemented, for example, using a machine or tangible computer-readable medium or article which may store an instruction or a set of instructions that, if executed by a machine, may cause the machine to perform a method and/or operations in accordance with the embodiments. Such a machine may include, for example, any suitable processing platform, computing platform, computing device, processing device, computing system, processing system, computer, processor, or the like, and may be implemented using any suitable combination of hardware and/or software. The machine-readable medium or article may include, for example, any suitable type of memory unit, memory device, memory article, memory medium, storage device, storage article, storage medium and/or storage unit, for example, memory, removable or non-removable media, erasable or non-erasable media, writeable or re-writeable media, digital or analog media, hard disk drive, floppy disk, Compact Disk Read Only Memory (CD-ROM), Compact Disk Recordable (CD-R), Compact Disk Rewriteable (CD-RW), optical disk, magnetic media, magneto-optical media, removable memory cards or disks, various types of Digital Versatile Disk (DVD), a tape, a cassette, or the like. The instructions may include any suitable type of code, such as source code, compiled code, interpreted code, executable code, static code, dynamic code, encrypted code, and the like, implemented using any suitable high-level, low-level, object-oriented, visual, compiled and/or interpreted programming language.

[0098] Various embodiments may be implemented using hardware elements, software elements, or a combination of both. Examples of hardware elements may include processors, microprocessors, circuits, application specific integrated circuits (ASIC), programmable logic devices (PLD), digital signal processors (DSP), field programmable gate array (FPGA), logic gates, registers, semiconductor device, microchips, chip sets, et cetera. Examples of software may include software components, programs, applications, computer programs, application programs, system programs, machine programs, operating system software, mobile apps, middleware, firmware, software modules, routines, subroutines, functions, computer implemented methods, procedures, software interfaces, application program interfaces (API), methods, instruction sets, computing code, computer code, et cetera.

[0099] The pig may be arranged to communicate using wireless systems, wired systems, or a combination of both. When implemented as a wired system, the system may include components and interfaces suitable for communicating or wired communications media, such as input/output (I/O) adapters, physical connectors to connect the I/O adapter with a corresponding wired communications medium. When implemented as a wireless system, the system may include components and interfaces suitable for communicating over a wireless shared media, such as one or more antennas, transmitters, receivers, transceivers, amplifiers, filters, control logic, and so forth. An example of wireless shared media may include portions of a wireless spectrum, such as the RF spectrum and so forth. A wireless communication device may be included in order to transmit and receive signals using various suitable wireless communications techniques. Such techniques may involve communications across one or more wireless networks.

[0100] Exemplary wireless networks include, but are not limited to, cellular networks, wireless local area networks (WLANs, cfr. WiFi, LiFi), wireless personal area networks (WPANs), wireless metropolitan area network (WMANs), satellite networks, et cetera. In communicating across such networks, the transmitter may operate in accordance with one or more applicable standards in any version.

[0101] However, other modifications, variations, and alternatives are also possible. The specifications, drawings and examples are, accordingly, to be regarded in an illustrative sense rather than in a restrictive sense.

[0102] For the purpose of clarity and a concise description features are described herein as part of the same or separate embodiments, however, it will be appreciated that the scope of the invention may include embodiments having combinations of all or some of the features described.

[0103] In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word ‘comprising’ does not exclude the presence of other features or steps than those listed in a claim. Furthermore, the words ‘a’ and ‘an’ shall not be construed as limited to ‘only one’, but instead are used to mean ‘at least one’, and do not exclude a plurality. The mere fact that certain measures are recited in mutually different claims does not indicate that a combination of these measures cannot be used to an advantage.