Transducer Housing Research Articles

Ultrasonic transducer with low cavitation

An ultrasonic sonar transducer ( 10 ) for facilitating transmission and reception of sonar signals, particularly at high speeds. The sonar transducer includes a transducer element ( 12 ) and a transducer housing ( 14 ). The housing includes a bottom wall ( 34 ) that is continuously curved with no major portion thereof parallel to the bottom face of the element. The bottom wall has a recessed portion ( 40 ) that partially forms an acoustic window for facilitating the transmission and reception of acoustic energy, with the acoustic window having a thickness approximately equal to one half or an integer multiple of one half of the wavelength of the acoustic energy. The bottom is preferably bow-shaped to create a positive angle of attack relative to the oncoming water, thereby promoting a laminar flow that reduces turbulence and cavitation and therefore nearly eliminates undesirable attenuation and reflection of transmitted and received energy.

Two-dimensional phased array ultrasound transducer with a convex enviromental barrier

A two-dimensional phased array ultrasound transducer comprises a transducer housing, a sensor mounted within the housing, and a convex environmental barrier for placement against, and maximizing contact with, a patient's body. The environmental barrier does not necessarily provide any focusing capability, therefore the propagation velocity of sound through the environmental barrier is approximately equal to the propagation velocity of sound through tissue of the patient's body.

Evaluation and Performance Enhancement of a Pressure Transducer under Flows, Waves, and a Combination of Flows and Waves*

Abstract The performance of a pressure transducer, with its inlet attached to differing hydromechanical front ends, has been evaluated in flow flume and wave flume experiments in which laminar and turbulent flows, and regular progressive gravity waves and combinations of flows and waves, were generated. For steady laminar flows, and for waves propagating on quiescent waters, the transducer’s performance improved when the inlet was at the center and flush with a large, thin, and smooth circular horizontal end plate. This enhancement is likely to have been achieved because of the isolation of the pressure inlet from the separated flows and vortices generated by the transducer housing. Flow disturbances, generated by nearby solid structures, deteriorated the performance of the pressure transducer. However, its performance could be significantly improved by protecting the pressure inlet by a sturdy, curved perforated shield. The dynamic pressure error in this case was 2 mb at 100 cm s−1, compared to 8 mb in t...

Flow patterns in an ultrasonic liquid flow meter

Flow visualisation studies have been undertaken for the case of an in-line, ultrasonic transducer housing in a cylindrical cross-section metering duct by direct observation of injected dye and of particles illuminated by a laser sheet. Results are presented for single and three bluff-body strut attachment of the transducer housing to the duct wall at Reynolds numbers (based on mean velocity and meter duct diameter) of 750, 1900 and 7950. Transducer face and wall fillet recirculation zones were dependent on the number of attachment struts and on the flow rate. The results are discussed in terms of their consequences for the performance of an ultrasonic transit time flow meter.

Advanced sensitivity calibration of the Los Angeles strong motion array

Results are presented of recent sensitivity calibration of 76 accelerographs (SMA-1) of the Los Angeles Strong Motion Array. These have pendulum-like transducers and optical recording system. One characteristic of their design is off-axis sensitivity, which is magnified by transducer misalignment. A new calibration procedure was applied, which considers off-axis sensitivity and measures the angles of misalignment (φ and ψ), as well as the incident angle of the light beam onto the film (θ 0 ). These are required (1) for accurate estimation of sensitivity, and (2) for proper instrument correction of recorded accelerograms which considers also cross-axis sensitivity and misalignment. These effects are important near large acceleration peaks (approaching and exceeding 1g), e.g. like the ones recorded near the source of the 1994 Northridge earthquake (M L = 6.4). This earthquake was recorded by 65 stations of the Los Angeles Strong Motion Array, at epicentral distances from 2 to 85 km. Histograms showing distribution of the misalignment angles, light beam incidence angle θ 0 (for unloaded position) and the transducer sensitivities are presented. These indicate that the misalignment angles are typically 1-1.5°, but may also be 3-4°. Angle θ 0 (usually neglected), is mostly between ± 8°, but may reach ±12°. Assuming θ 0 = 0 leads to systematically smaller values of the measured sensitivity (e.g. by ∼3% for θ 0 = 8° and ∼4% for θ 0 = 12°). Comparison of the newly measured sensitivities with those measured prior to installation (in 1979/1980), s old , shows that, in general, the new values are systematically smaller. The difference is typically within 5 per cent, but in some cases is as large as 10 per cent. Other principal sources of the observed differences and their mechanisms are discussed. Those include long-term changes in the transducers (e.g. change of stiffness, reflected in changes of the natural frequency) and differences in the calibration procedure (e.g. errors associated with manual reading film records with tilt test data, and with transducer and instrument housing misalignment). The presented results may be considered typical of similar strong motion arrays worldwide.

Technical aspects of mechnomyography recording with piezoelectric contact sensor.

The piezoelectric contact sensor has been widely utilised in mechanomyography (MMG). The authors aim to clarify the mechanical variables (i.e. acceleration, velocity or displacement) reflected by the MMG signal detected with a piezoelectric contact sensor (PEC), and compare the results with those obtained simultaneously by an accelerometer (ACC). To measure the acceleration-frequency response, a mechanical sinusoidal excitation of 5 to 300 Hz at a constant magnitude of 0.01 G was applied to the two transducers. The acceleration-frequency response of the ACC transducer was confirmed to be almost flat. The PEC without any restriction of the transducer housing (including the combined seismic mass) demonstrated a similar response to the ACC transducer. The PEC transducer output with restricted housing decreased with increasing sinusoidal frequency and an attenuation slope of -40 dB/decade and phase angle of -180 degrees. The voluntary MMG signal during isometric knee extension was recorded simultaneously with the two transducers. The amplitude spectral density distribution of the MMG from the PEC transducer was narrow and the mean frequency was approximately one-half that obtained from the ACC transducer. The amplitude spectral density distribution with the PEC transducer resembled that of the double integral over time of the ACC transducer signal. The phase angle of the PEC transducer signal was different from that of the ACC transducer signal by approximately -180 degrees. These results suggest that the PEC transducer acts as a displacement meter of muscle vibration. In addition, differences in the MMG frequency components relating to the transducer type must be taken into consideration when investigating the mechanical activity of muscle.

In Vivo Results with a New Device for Ultrasonic Monitoring of Pig Skin Cryosurgery: The Echographic Cryoprobe

One of the main difficulties encountered in cryosurgery is the uncertainty in the extent and depth of the tissue effectively treated during the freezing process. The objective of this study was to evaluate in vivo ultrasonic control of skin cryosurgery using a new echographic cryoprobe. An echographic cryoprobe, developed specifically for dermatology applications, combines a high-frequency (20 MHz) miniature ultrasonic transducer and a N2O-driven closed cryoprobe. Knowledge of the ultrasound velocity of frozen skin is a prerequisite for monitoring the iceball formation kinetics. Therefore, in a first study, we estimated the ultrasound velocity of frozen skin specimens. In a second step, the operation of the echographic cryoprobe was assessed, under in vivo conditions similar to those used in human therapeutics, on normal skin of three female "Large-White" pigs under anesthesia. The mean value of ultrasound velocity of frozen skin obtained by pooling the data from all the skin specimens included in this study was 2865 +/- 170 m per s. The average rates of growth (10(-2) mm per s) of the iceballs were found to be 12.2 +/- 1.0 (pig 1), 9.0 +/- 1.0 (pig 2), and 8.4 +/- 0.9 (pig 3). The echographic cryoprobe had a built-in high-frequency ultrasonic transducer that served two functions. It enabled in vivo real-time monitoring of depth penetration of the iceball and it gave important feedback to the operator or to the console relating to the rate of growth of the iceball. Automatic (i.e., operator-independent) detection of the echo signal from the freezing front and calculation of the depth penetration of the iceball was possible.

Method and apparatus for positioning and ultrasonic transducer and a display screen

Disclosed herein is a system for positioning an ultrasonic transducer where the user can see the positioning device and a display of the image being generated at the same time. This system solves the problem of the user having to look away from the transducer to see the image. The method comprises positioning a display screen to show the ultrasonic image being generated to the user such that the user can see the positioning of the transducer and the image on the display screen at the same time. To accomplish this the display screen can be incorporated into or mounted directly mounted onto the transducer housing. Once the user properly positions the transducer and is satisfied with the image, a image capture signal can be sent by the user. Once the image is captured it can be sent to an associated computer for analysis, printed or saved for archiving, etc.

Quality Control for Real-Time Ultrasound Equipment

A quality control program for the routine monitoring of real-time ultrasound equipment is described. To be effective, the quality control program must incorporate performance tests that are most likely to detect common system problems. These selective tests include assessment of penetration, distance accuracy, uniformity, and fidelity of image recording. A tissue equivalent phantom with an attenuation rate of 0.7 dB/MHz/cm is recommended for quality control testing. Mechanical inspection of transducer housing, connector, power cord, and console must also be conducted.

High gain acoustic transducer

A high gain acoustic transducer (200) is formed of a voice coil (218) and a magnetic material (238) housed within a transducer housing (202). The transducer housing (202) includes flexible, symmetrical dome halves (204, 206). Vibrations of the magnetic material (238) of the transducer (200) induce a current in the voice coil (218). Alternatively, electrical signals applied to the voice coil (218) induce vibrations in the transducer (200). The voice coil (218) is supported by a first (204) of the two dome halves by way of a first support assembly (214), and the magnetic material (238) is supported by a second (206) of the two dome halves by way of a second support assembly (232). The housing (202) forms a watertight enclosure, and the transducer (200) may be utilized in underwater applications.

Water‐resistant transducer housing with hydrophobic vent

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Electromechanical transducer for implantable hearing aids

Electromechanical transducer for implantable hearing aids. The transducer has a hermetically sealed and biocompatible housing, in which a wall is designed as a membrane that can oscillate, and which forms a heteromorphic connecting element together with a piezoelectric ceramic disk. Mechanical oscillations of the housing membrane are coupled to the middle ear or inner ear of the user by a mechanically rigid element attached in the central area of the membrane. This element is configured as a bow, so that in positioning the transducer housing from the direction of the mastoid adjoining the tympanic cavity, it acts as an artificial anvil to which coupling elements can be attached for mechanically transmitting oscillations of this artificial ossicle to the inner ear. Various coupling elements can be used, which correspond to the respective individual pathological situation. The application of the entire transducer system can be performed the operating surgeon having an unobstructed view, without extensive, space-creating interventions in the anatomical conditions of the middle ear.

Optical pressure transducer

This paper presents the characteristics of an optical pressure transducer using fiber optics. The transducer consists of a cylindrical housing with a reflective mylar diaphragm attached at one end and fiber-optic bundle at the other. The fiber-optic bundle used is the bifurcated type, in which two bundles of randomly distributed fibers are joined at one end to form a Y-shaped geometry. The common end is attached to the end of the transducer housing, opposite to the diaphragm. At the branched ends, one bundle is connected to a dc light source, while the other bundle carries the light reflected from the diaphragm to a photodetector. By keeping the input light source at constant intensity, the amount of reflected light depends on the distortion of diaphragm due to pressure differential across the diaphragm surface. This pressure transducer can measure both the static pressure level and the fluctuating pressure. A simple ‘‘homemade’’ diaphragm was used in this experiment, and a sensitivity of approximately 10 mV per mm Hg was obtained over a range of 20 mm Hg. The dynamic response was linear to about 2 kHz. Both the sensitivity and the frequency response can be much increased by improving the diaphragm performance.

Analysis and testing of a concentric ring applicator for ultrasound hyperthermia with clinical results

A planar ultrasound transducer was modified by etching concentric circles on one surface of a piezoelectric ceramic to create four rings. The 10 cm diameter transducer had four active rings and an unenergized centre. The transducer housing was designed to be completely immersed in fluid, suitable for intraoperative hyperthermia. The transducer was resonant at 1.0 MHz and was tested in a water tank and in an acoustic absorbing medium where the steady-state temperatures were measured. A comparison between a single 10 cm element and the concentric ring modification with all rings at equal power density showed the performance to be nearly identical. In vivo experiments in canine thigh verified the phantom predictions as individual rings were energized. Theoretical intensity calculations were made and compared favourably to water tank test results. Clinical hyperthermia treatments for chest wall and head and neck tumours showed that the temperature distribution could be highly modified by adjusting the power to individual rings while holding the transducer stationary. Automated temperature mapping parallel to the transducer face was used to compare a single element applicator to the concentric ring applicator in clinical treatments on the same lesion. The concentric ring applicator was radially adjustable and was found to be advantageous in lowering the central peak temperatures and flattening the temperature distribution in tumours. A comparison between the single element clinical and operating room series showed that when pain is removed as a treatment limiting factor, higher central tumour temperatures are possible and more of the tumour volume achieves therapeutic temperatures. The concentric ring design improves the temperature distribution such that the higher central temperatures will not be necessary.

Effects of Arching on Response Time of Miniature Pore Pressure Transducer in Clay

Abstract A study of the response time of miniature pore pressure transducers embedded in clay soils is presented. The highly nonuniform pore pressure distributions around the transducers due to arching and stress concentration can have a significant effect on transducer response especially when the surrounding soil is loaded anisotropically. This is caused by the difference in compressibility of the soil and the transducer housing. Finite-element analysis and experimental results confirm the importance of these effects. A spherical porous stone or a cylindrical stone with top and side drainage results in significant reduction in response time and in overshoot due to arching effects.

Transducer system for the noninvasive recording of arterial pressure contours

A transducer system is described that permits noninvasive recordings of the pressure-vs-time arterial profile at any palpable site on the body. A thin (30 microns) piezoelectric polymer film of polyvinylidene fluoride serves as the active element and as the mechanical coupler to the skin. The system has high frequency response and a low frequency cut-off of 0.16 Hz. The active element and its support provides a good mechanical impedance match with the skin. The transducer housing resembles a thick wrist watch and is strapped in place. The complete system is designed to record as many as four simultaneous profiles on a subject. Comparisons of the noninvasive transducer records with records taken with an indwelling catheter indicate congruence of the two signals and the first and second derivatives of the two signals, both when the transducer is applied directly to the skin and when a layer of fat is interposed between the skin and the transducer. The system provides a simple atraumatic means of periodically screening and/or monitoring cardiovascular changes in large populations of subjects and would provide a means of tracking changes induced by therapeutic programs.

Seismic transducer baseplate and housing assembly

Une structure de plaque d'embase et d'enceinte rigide, legere, pour un transducteur sismique. A base plate structure and a rigid enclosure, light for a seismic transducer. La plaque d'embase (12) comprend un moyeu central (26) de reception d'une bielle de piston inferieure (70). The base plate (12) comprises a central hub (26) for receiving a lower piston rod (70). Des plaques superieure et inferieure (32 et 36) s'etendent radialement a l'exterieur a partir du moyen central (26). The upper and lower plates (32 and 36) extend radially from the outside of the central means (26). Une pluralite de plaques de renforcement egalement espacees angulairement (40) s'etendent egalement radialement vers l'exterieur a partir du moyeu (26), leurs bords superieurs et inferieurs etant relies aux plaques superieure et inferieure. A plurality of reinforcement plates also spaced angularly (40) also extend radially outwards from the hub (26), upper and low edges being subsequently assembled in the upper and lower plates. Un ensemble d'enceintes (78) relie rigidement une bielle de piston superieure (74) a la plaque d'embase (12), et comprend une section tronconique (82). A set of speakers (78) rigidly connects an upper piston rod (74) to the base plate (12), and includes a frustoconical section (82). La structure formee de l'enceinte rigide legere (78) et de la plaque d'embase (12) constitue un transducteur sismique ayant une distribution de force en phase sur sensiblement toute la region de la plaque d'embase lorsqu'elle est en contact avec le sol. The structure formed of the rigid enclosure slight (78) and the base plate (12) is a seismic transducer having in-phase force distribution over substantially the entire area of ​​the base plate when in contact with the ground.

Medical applications of silicon sensors.

For invasive medical sensors, silicon sensors have a number of specific advantages: miniaturisation, low cost, high flexibility, high reliability, choice of parameter, packaging and integration of electronics. Specific packaging problems for microtransducer catheters (MTCS) whereby the transducer is a silicon sensor are related to the construction of the transducer housing and choice of materials. The main object is to maintain the sensitivity of the silicon sensor for the specific parameter while designing a proper housing. This is illustrated by describing solutions for pressure- and oxygen-sensitive MTCSs. Two sets of factors which promote the use of MTCS in hospitals are discussed. The first is the quality of signal and the possibility of continuous monitoring of the measured parameter. The second comprises patient comfort, simpler application techniques and economic factors.

Bowed elastomeric window

A window for a sonar transducer housing is formed of an elastomeric plate which is bonded to a mounting ring for securing the window to the housing. The plate is bowed with a convex shape during the molding and the curing of the elastomer. During assembly of the housing, the convex surface of the plate faces inwardly and is depressed to a substantially planar configuration by the pressure of oil within the housing. The compression of the elastomer against the mounting ring inhibits separation of the elastomer from the ring.

Acoustic transducer housing

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