- Email: [email protected]
Integrated processing with the JUKEBOX ultrasonic imaging system
Ultrasonics International 87 abstracts transverse velocity is 3200 m s - 1 ) , four different depths of focus, with an aperture of 16 transducers centered between two transducers, or centered in the middle of one transducer. These 512 shots enable us to build an image of 128 lines oriented at 45 ° . The information delivered by each shot is stored in an electronic memory of 128 x 156 pixels of 16 levels (4 bits) after classical echographic treatment, i.e. a time-gain control of the echographic signal, detection and logarithmic compression. The image is read and delivered with classical -IV scanning, Theoretical and experimental evaluation of the prototype is presented: measurements are carried out with defects in holes drilled in a steel block, parallel to the face of investigation. Several non-destructive testing applications are shown (fatigue cracks measurements or evaluation defects in welds). Results obtained from this imaging device seem competitive in comparison with other techniques. The quality of the image is guaranteed by a lateral resolution which remains as low as 3 mm, at 6 dB for any depth.
dynamic range up to high frequencies. However, a high resolution requires a large number of digital steps, i.e. many comparators with memories. For example, a 4-bit digital peak detector has 16 amplitude steps and, therefore, 16 comparators with 16 memories. That is why the DFVLR looked for another method allowing digital peak amplitude measurements with high resolution, which should not require a large number of electronic devices. The new method is based on a modified counting A/D-converter. The device consists of a w i n d o w comparator with outputs connected to a memory. The reference voltage is changed step by step until its value is as large as the peak amplitude of the signal within the gate. The reference voltage is produced by a logarithmic D/A-converter which is connected with a counter. The clock frequency of this up/down counter is equal to that of the gate pulses. The features of the new developed peak detector, HFUS 1050, are: frequency range, 1 100 MHz; resolution, 1 dB; dynamic range, 31 dB.
Measuring turbulent flow characteristics using a Depth characterization with radiation field theory
multi-dimensional ultrasonic probe
D.K. Mak and I.R. Somerville, Canada Centre for Mineral and Energy Technology, Ottawa, Canada
J. Y. Cheung, K.J. Dormer and A. Ashrafzadeh, University of Oklahoma, Norman, USA
Ultrasonic spectral analysis has been used to determine the size and shape of a scattering discontinuity. An appropriate theoretical framework has to be developed for analysing the spectrum of an ultrasonic echo. Theoretical understanding of the flaw response is limited to a highly restricted class of flaws. Frequency minima obtained from spectral analysis can be used to characterize the shape, size and orientation of the defect. It will be pointed out here that the equations of the orientational dependence of the ultrasonic spectrum of the discontinuity response used by previous workers were not correctly derived. A new set of equations are derived using radiation field theory based on Huyghen's principle. Flat circular voids were used as examples. The equations can apply to a single pulse-echo transducer or the more general case of two transducers acting as transmitter- receiver system. Computer polar plots were drawn for the sound pressure profile of the scattered signal for different orientation of the scatterer. Experimental data have been collected for the double transducer system. The spectrum data agree quite well with the results of theoretical calculation.
This study demonstrates the feasibility of turbulent flow characteristics measurement using a dual transducer ultrasonic probe and compares its performance in measuring flow volume rate with other conventional techniques in a bench mark test done in vitro. The use of a multi-dimensional pulsed Doppler ultrasonic probe was effective in eliminating the need to know the Doppler angle between the transducer axes and the flow direction. For a single transducer probe, the Doppler angle was usually assumed because it cannot be measured. For a dual or triple transducer probe, the Doppler angle can be directly measured resulting in more accurate estimation of the velocity data. Such a dual transducer probe was designed and made. Since instantaneous velocity measurements were obtained, other turbulent characteristics such as shear stress and friction factor were also computed. To calibrate the probe and to compare its performance with other techniques, an in vitro experiment is set up using a pulsatile pump. A section of a dog's vessel was connected to the pump through a narrow orifice that generated turbulence. On the vessel, the dual transducer probe, a pulse transit time probe, and an electromagnetic probe were also attached. Flow rates ranging between 0 to 200 ml min 1 were used. Both laminar flow (without the orifice), and turbulent flow (with the orifice) conditions were tested with varying flow rates and pulse rates. By changing the size of the orifice, varying degrees of turbulence were created. Results showed that the dual transducer probe consistently provided the smallest error (3 5%) over the range of flow rates, pulse rates, and varying degrees of turbulence tested when compared to the other techniques. Such a low error rate was expected and was consistent with theoretical analyses. The transit time probe and the single transducer probe gave acceptable performance with slightly larger error. The performance of the doctro-magnetic probe was less acceptable due to its sensitivity to environment and random flow especially in highly turbulent conditions.
A high frequency peak detector for u.s. test pulses
W. Hillger, DFVLR Institut, Braunschweig, FRG The proportional monitor used in standard commercial flaw detectors determines the peak value of the higher u.s.-echo within the gate. The passive peak measurement method is often not sufficiently accurate for the detection of defects, particularly if the data must undergo further computer processing. The problem can be restricted to fast amplitude detection and storage of the value until the next measurement. Due to the relatively short pulse duration of 10 - 5 10 8 s, it is unfortunate to use the standard active peak value measurement methods of electrical engineering where the diode curve is extensively linearized using operation amplifiers. The advantage of digital methods over analog ones is a fast response time and that there are no changes in the memory after data acquisition, such as would happen, for example, in the case of analog memories with capacitances. However, the application of fast A/D-converters also requires calculation of the peak value, since converters sample the whole u.s.-signal as a sequence of separate points and do not determine the maximum level directly. For peak detection a modified flash converter is suitable, which yields a high
Integrated processing with the JUKEBOX ultrasonic imaging system
G. Corneloup, B. Comu, M. Perdrix and I. Magnin, CEN Cadarache, Saint Paul-lez-Durance, France JUKEBOX is a system for displaying and interpreting ultrasonic measurements designed to ensure compatibility with
Ultrasonics 1987 Vol 25 November
381
Ultrasonics International 87 abstracts advanced digital techniques developed in non-destructive test laboratories. The system environment frees the operator to a large extent from the tasks involved in managing megabytes of data. The open-ended modular design allows many different signal and image processing routines to be included or combined. Qualification testing is in progress for gray-level image matrix filtering methods and various imaging algorithms based, for example, on relational criteria or signal dynamics. The operator is guided in selecting the available options by a structured menu-driven environment. Various data representation modes (1,2 or 3 dimensions, with or without binary compression) are taken into account by the system at every step in the analysis. The first experimental application of the J U KEBOX system, in response to immediate laboratory requirements, involves the examination of small austenitic stainless steel weld seams a few millimeters thick. Experimental results on artificial defects will be submitted.
Ultrasonic wattmeter
S. Kaneko, M. Gakumazawa and K. Shinoda, Shibaura Institute of Technology, Tokyo, Japan A multiplication-type ultrasonic wattmeter was developed for the ultrasonic frequency region. This applied the fact that the power was represented by the product of the current and the voltage, the phase in a high frequency electric circuit. A probe was made to detect the signal from the current and the voltage, and connected with the X and Y terminals of a multiplier IC. A d.c. voltage proportioned to the power was drawn through a low-pass filter from the output signal of the IC. Unlike most wattmeters, use in the frequency range 5 - 4 0 0 kHz was possible and a high power load could be measured. The outline and characteristics of this wattmeter are reported and its uses illustrated by demonstration.
Numerical simulation of ultrasonic fkowmeters
A. Lygre, P. Lunde, V. Berge and M. Vestrheim, Chr. Michelsen Institute, Bergen, ,Norway Ultrasonic flowmeters for measuring high-pressure natural gas flows potentially offer several advantages compared to conventional meters. However, the development of ultrasonic gas flowmeters to the stage of producing highprecision instruments applicable for custody transfer of natural gas presents a number of technical challenges, including improvements in ultrasonic transducer technology, a better understanding of ultrasonic pulse propagation across a pipe flow and further developments in signal detection and processing techniques. To optimize the design of ultrasonic flowmeters, and thus improve current ultrasonic flowmeter technology. A numerical simulation model is being developed for a single-beam ultrasonic flowmeter. We present a model and discuss the results obtained with it, with special emphasis on practical aspects of designing ultrasonic flowmeters for high-pressure natural gas. The model consists of a signal generator, electrical matching networks, and transmitting and receiving transducers separated by a flowing fluid layer. Combining electro-acoustic network descriptions and acoustic propagation models in the time and frequency domains, the signal can be traced between the various models of the network, and the effects of signal shaping techniques, transducer design and flow characteristics, such as fluid speed and hydrostatic pressure, can be studied. We also address the problem of designing industrial transducers for operation in high-pressure natural gas environ-
382
Ultrasonics 1987 Vol 25 November
ments, Gas leakage into the transducers must be avoided, and this can be achieved by metal encapsulation of the transducers. However, the accompanying impedance mismatch reduces transducer efficiency. By computer studies, applying the simulation model, we demonstrate how transducer efficiency can be improved by employing suitable matching and backing layers.
An acoustic method for high 3recision gas flow measurements
M. Knuuttila and P. HiismakJ Technical Research Centre of Finland, Espoo, Finland According to recent findings propagation of long acoustic waves in guides of rigid walls is insensitive to the velocity profile of the flow. The speed of sound in the presence of flow is the speed of sound in the absence of flow plus, in the downstream propagation, or minus, in the upstream propagation, the mean flow velocity over the guide crosssection. This is in contrast to short acoustic waves, typically in ultrasonic flow measurements, which are known to be strongly dependent on the velocity profile of the flow. An experimental set-up is described for testing the feasibility, accuracy and the range of gas flow measurement in a pipe of 56.3 mm i.d. By an inverter driven blower the flow could be adjusted in the range 0 - 3 2 m s 1. Sound was fed into the pipe by miniature bass loudspeakers as broad-band frequency sweeps up to 3.0 kHz chosen slightly less than the cut-off frequency of the pipe, 3.6 kHz. Detection was by miniature microphones mounted in appropriate holes through the pipe wall. Upstream and downstream transit times were measured from the microphone signals by a fast polarity corretator. In this way transit times could be measured with high accuracy in a few seconds without significant interference from the environmental noise. A vortex flowmeter of the type Endress & Hauser DMV 6330 was used as a reference. The results 'of the measurements were very promising showing errrors from 0.4 to 0.1% as the flow velocity was in the range 0.2-32 m s 1. The correlation coefficient between the acoustic method and the vortex gauge was r 2 = 0.9994 in the range of vortex gauge 3 - 1 0 m s 1.
Low frequency ultrasonic contrapropagating transit time system for gas flowmetering
K.S. Mylvaganam, R. Boe and T. Folkestad, Chr. Michelsen Institute, Bergen-Fantoft, Norway The transit time method using two contrapropagating ultrasonic signals is well known in the flowmetering technology. However, there is a resurgence of interest for this technique both in flue-gas analysis as applied to environmental technology and in normal gas flowmetering. This poster presents a gas flowmeter using the above technique and covers the following: (1) specially designed transducers for the system; (2) signal processing system that uses technique used in radar; (3) set of results for comparison from extensive wind tunnel tests. The system was developed to cater for high velocity variations and was found from wind tunnel tests to have fulfilled the requirements of large dynamic range of flow velocity, large dimensions of conduit sustaining the flow and good signal-to-noise ratio. The system performance is finally given in a form in which linearity can be seen against a standard calibration instrument. All the necessary analysis for the operation of the system is also given.
dynamic range up to high frequencies. However, a high resolution requires a large number of digital steps, i.e. many comparators with memories. For example, a 4-bit digital peak detector has 16 amplitude steps and, therefore, 16 comparators with 16 memories. That is why the DFVLR looked for another method allowing digital peak amplitude measurements with high resolution, which should not require a large number of electronic devices. The new method is based on a modified counting A/D-converter. The device consists of a w i n d o w comparator with outputs connected to a memory. The reference voltage is changed step by step until its value is as large as the peak amplitude of the signal within the gate. The reference voltage is produced by a logarithmic D/A-converter which is connected with a counter. The clock frequency of this up/down counter is equal to that of the gate pulses. The features of the new developed peak detector, HFUS 1050, are: frequency range, 1 100 MHz; resolution, 1 dB; dynamic range, 31 dB.
Measuring turbulent flow characteristics using a Depth characterization with radiation field theory
multi-dimensional ultrasonic probe
D.K. Mak and I.R. Somerville, Canada Centre for Mineral and Energy Technology, Ottawa, Canada
J. Y. Cheung, K.J. Dormer and A. Ashrafzadeh, University of Oklahoma, Norman, USA
Ultrasonic spectral analysis has been used to determine the size and shape of a scattering discontinuity. An appropriate theoretical framework has to be developed for analysing the spectrum of an ultrasonic echo. Theoretical understanding of the flaw response is limited to a highly restricted class of flaws. Frequency minima obtained from spectral analysis can be used to characterize the shape, size and orientation of the defect. It will be pointed out here that the equations of the orientational dependence of the ultrasonic spectrum of the discontinuity response used by previous workers were not correctly derived. A new set of equations are derived using radiation field theory based on Huyghen's principle. Flat circular voids were used as examples. The equations can apply to a single pulse-echo transducer or the more general case of two transducers acting as transmitter- receiver system. Computer polar plots were drawn for the sound pressure profile of the scattered signal for different orientation of the scatterer. Experimental data have been collected for the double transducer system. The spectrum data agree quite well with the results of theoretical calculation.
This study demonstrates the feasibility of turbulent flow characteristics measurement using a dual transducer ultrasonic probe and compares its performance in measuring flow volume rate with other conventional techniques in a bench mark test done in vitro. The use of a multi-dimensional pulsed Doppler ultrasonic probe was effective in eliminating the need to know the Doppler angle between the transducer axes and the flow direction. For a single transducer probe, the Doppler angle was usually assumed because it cannot be measured. For a dual or triple transducer probe, the Doppler angle can be directly measured resulting in more accurate estimation of the velocity data. Such a dual transducer probe was designed and made. Since instantaneous velocity measurements were obtained, other turbulent characteristics such as shear stress and friction factor were also computed. To calibrate the probe and to compare its performance with other techniques, an in vitro experiment is set up using a pulsatile pump. A section of a dog's vessel was connected to the pump through a narrow orifice that generated turbulence. On the vessel, the dual transducer probe, a pulse transit time probe, and an electromagnetic probe were also attached. Flow rates ranging between 0 to 200 ml min 1 were used. Both laminar flow (without the orifice), and turbulent flow (with the orifice) conditions were tested with varying flow rates and pulse rates. By changing the size of the orifice, varying degrees of turbulence were created. Results showed that the dual transducer probe consistently provided the smallest error (3 5%) over the range of flow rates, pulse rates, and varying degrees of turbulence tested when compared to the other techniques. Such a low error rate was expected and was consistent with theoretical analyses. The transit time probe and the single transducer probe gave acceptable performance with slightly larger error. The performance of the doctro-magnetic probe was less acceptable due to its sensitivity to environment and random flow especially in highly turbulent conditions.
A high frequency peak detector for u.s. test pulses
W. Hillger, DFVLR Institut, Braunschweig, FRG The proportional monitor used in standard commercial flaw detectors determines the peak value of the higher u.s.-echo within the gate. The passive peak measurement method is often not sufficiently accurate for the detection of defects, particularly if the data must undergo further computer processing. The problem can be restricted to fast amplitude detection and storage of the value until the next measurement. Due to the relatively short pulse duration of 10 - 5 10 8 s, it is unfortunate to use the standard active peak value measurement methods of electrical engineering where the diode curve is extensively linearized using operation amplifiers. The advantage of digital methods over analog ones is a fast response time and that there are no changes in the memory after data acquisition, such as would happen, for example, in the case of analog memories with capacitances. However, the application of fast A/D-converters also requires calculation of the peak value, since converters sample the whole u.s.-signal as a sequence of separate points and do not determine the maximum level directly. For peak detection a modified flash converter is suitable, which yields a high
Integrated processing with the JUKEBOX ultrasonic imaging system
G. Corneloup, B. Comu, M. Perdrix and I. Magnin, CEN Cadarache, Saint Paul-lez-Durance, France JUKEBOX is a system for displaying and interpreting ultrasonic measurements designed to ensure compatibility with
Ultrasonics 1987 Vol 25 November
381
Ultrasonics International 87 abstracts advanced digital techniques developed in non-destructive test laboratories. The system environment frees the operator to a large extent from the tasks involved in managing megabytes of data. The open-ended modular design allows many different signal and image processing routines to be included or combined. Qualification testing is in progress for gray-level image matrix filtering methods and various imaging algorithms based, for example, on relational criteria or signal dynamics. The operator is guided in selecting the available options by a structured menu-driven environment. Various data representation modes (1,2 or 3 dimensions, with or without binary compression) are taken into account by the system at every step in the analysis. The first experimental application of the J U KEBOX system, in response to immediate laboratory requirements, involves the examination of small austenitic stainless steel weld seams a few millimeters thick. Experimental results on artificial defects will be submitted.
Ultrasonic wattmeter
S. Kaneko, M. Gakumazawa and K. Shinoda, Shibaura Institute of Technology, Tokyo, Japan A multiplication-type ultrasonic wattmeter was developed for the ultrasonic frequency region. This applied the fact that the power was represented by the product of the current and the voltage, the phase in a high frequency electric circuit. A probe was made to detect the signal from the current and the voltage, and connected with the X and Y terminals of a multiplier IC. A d.c. voltage proportioned to the power was drawn through a low-pass filter from the output signal of the IC. Unlike most wattmeters, use in the frequency range 5 - 4 0 0 kHz was possible and a high power load could be measured. The outline and characteristics of this wattmeter are reported and its uses illustrated by demonstration.
Numerical simulation of ultrasonic fkowmeters
A. Lygre, P. Lunde, V. Berge and M. Vestrheim, Chr. Michelsen Institute, Bergen, ,Norway Ultrasonic flowmeters for measuring high-pressure natural gas flows potentially offer several advantages compared to conventional meters. However, the development of ultrasonic gas flowmeters to the stage of producing highprecision instruments applicable for custody transfer of natural gas presents a number of technical challenges, including improvements in ultrasonic transducer technology, a better understanding of ultrasonic pulse propagation across a pipe flow and further developments in signal detection and processing techniques. To optimize the design of ultrasonic flowmeters, and thus improve current ultrasonic flowmeter technology. A numerical simulation model is being developed for a single-beam ultrasonic flowmeter. We present a model and discuss the results obtained with it, with special emphasis on practical aspects of designing ultrasonic flowmeters for high-pressure natural gas. The model consists of a signal generator, electrical matching networks, and transmitting and receiving transducers separated by a flowing fluid layer. Combining electro-acoustic network descriptions and acoustic propagation models in the time and frequency domains, the signal can be traced between the various models of the network, and the effects of signal shaping techniques, transducer design and flow characteristics, such as fluid speed and hydrostatic pressure, can be studied. We also address the problem of designing industrial transducers for operation in high-pressure natural gas environ-
382
Ultrasonics 1987 Vol 25 November
ments, Gas leakage into the transducers must be avoided, and this can be achieved by metal encapsulation of the transducers. However, the accompanying impedance mismatch reduces transducer efficiency. By computer studies, applying the simulation model, we demonstrate how transducer efficiency can be improved by employing suitable matching and backing layers.
An acoustic method for high 3recision gas flow measurements
M. Knuuttila and P. HiismakJ Technical Research Centre of Finland, Espoo, Finland According to recent findings propagation of long acoustic waves in guides of rigid walls is insensitive to the velocity profile of the flow. The speed of sound in the presence of flow is the speed of sound in the absence of flow plus, in the downstream propagation, or minus, in the upstream propagation, the mean flow velocity over the guide crosssection. This is in contrast to short acoustic waves, typically in ultrasonic flow measurements, which are known to be strongly dependent on the velocity profile of the flow. An experimental set-up is described for testing the feasibility, accuracy and the range of gas flow measurement in a pipe of 56.3 mm i.d. By an inverter driven blower the flow could be adjusted in the range 0 - 3 2 m s 1. Sound was fed into the pipe by miniature bass loudspeakers as broad-band frequency sweeps up to 3.0 kHz chosen slightly less than the cut-off frequency of the pipe, 3.6 kHz. Detection was by miniature microphones mounted in appropriate holes through the pipe wall. Upstream and downstream transit times were measured from the microphone signals by a fast polarity corretator. In this way transit times could be measured with high accuracy in a few seconds without significant interference from the environmental noise. A vortex flowmeter of the type Endress & Hauser DMV 6330 was used as a reference. The results 'of the measurements were very promising showing errrors from 0.4 to 0.1% as the flow velocity was in the range 0.2-32 m s 1. The correlation coefficient between the acoustic method and the vortex gauge was r 2 = 0.9994 in the range of vortex gauge 3 - 1 0 m s 1.
Low frequency ultrasonic contrapropagating transit time system for gas flowmetering
K.S. Mylvaganam, R. Boe and T. Folkestad, Chr. Michelsen Institute, Bergen-Fantoft, Norway The transit time method using two contrapropagating ultrasonic signals is well known in the flowmetering technology. However, there is a resurgence of interest for this technique both in flue-gas analysis as applied to environmental technology and in normal gas flowmetering. This poster presents a gas flowmeter using the above technique and covers the following: (1) specially designed transducers for the system; (2) signal processing system that uses technique used in radar; (3) set of results for comparison from extensive wind tunnel tests. The system was developed to cater for high velocity variations and was found from wind tunnel tests to have fulfilled the requirements of large dynamic range of flow velocity, large dimensions of conduit sustaining the flow and good signal-to-noise ratio. The system performance is finally given in a form in which linearity can be seen against a standard calibration instrument. All the necessary analysis for the operation of the system is also given.