Showing papers on "Transducer published in 1982"

Implantable dynamic pressure transducer system

Abstract: A pressure and motion transducer and cooperating circuitry for an implantable medical device are disclosed. The system includes a pressure transducer 48 and buffer amplifier 40. A clock 70 in pacer 52 periodically energises amplifier 40 via capacitor 62 and lead system 54. The voltage sensed across sensing resistor 74 at node 78 is applied to sample and hold circuit 66 and a continuous pressure signal is provided at output terminal 82.

Ultrasonic diagnostic and therapeutic transducer assembly and method for using

Abstract: An ultrasonic transducer assembly is provided with transducers for both therapeutic and diagnostic ultrasonic radiation. A moveable seal permits adjustment and alignment of the two transducer units in a fluid medium. In addition, there is provided a light beam directed along the axis of the ultrasonic radiation. The transducer assembly is particularly useful for ophthalmic therapy.

Teleconferencing method and system

Abstract: Control of teleconference is facilitated so as to allow relatively unskilled operators to implement such control. The invention includes at least a pair of teleconferencing sites, each of which includes at least a pair of controllable video sources for deriving video signals from controllable regions of the associated site, an audio source for deriving an audio signal from the associated site, at least a pair of video displays for controllably displaying either locally or remotely generated images, an audio transducer responsive to a remotely generated audio signal for generating perceptible sound, an interface for coupling digital representations of locally generated audio and video signals to a communication link linking the sites and for coupling digital representations of remotely generated audio and video signals, a control device including a digital microprocessor and controlling, among other things, a video matrix switch, the video matrix switch having plural video inputs and outputs for controllably coupling at least a locally generated video signal to the interface and for controllably coupling locally and/or remotely generated video to said displays. The control device also includes a control video display with a touch sensitive screen for controlling the video sources and video matrix switch in response to touches on the touch sensitive screen by an operator and further including, in the form of a program in said microprocessor, apparatus to interpret commands initiated by operator touches of the touch sensitive screen and for thereafter implementing the commands if elements of the command are consistent with each other and with available resources as well as message formatting which are responsive to the logic for formatting digital messages destined for the video sources and the video matrix switch.

An Analysis of SAW Interdigital Transducers with Internal Reflections and the Application to the Design of Single-Phase Unidirectional Transducers

Abstract: A new coupling-of-modes (COM) analysis of SAW interdigital transducers (IDTs) is presented. The analysis includes the effects of multiple reflections within a transducer. The fundamental equations are derived and some simple closed-form results a re given. In addition, some general properties having regard to the relative phase of transduction and reflection c oefficients within a transducer are derived. A new class of unidirectional transducers is proposed which require only one matching network and do not have the crossovers required in current three-phase designs. These single-phase unidirectional transducers (SWDTs) utilize internal r eflections within the transducer to achieve unidirectional behavior. Practical SWDT configurations are proposed and some experimental results presented. The application of the new COM analysis to synthesis is discussed.

Transoesophageal cross-sectional echocardiography with a phased array transducer system. Technique and initial clinical results.

Abstract: Cardiac imaging by transthoracic two dimensional echocardiography is impaired in patients with chronic lung disease, those with obesity, and those with abnormal chest wall configuration. In order to overcome these limitations, a miniature phased array ultrasound transducer fitted to the tip of a commercially available gastroscope was developed. Transducer position and orientation can be adjusted completely by external control of vertical displacement inside the oesophagus, rotation, and angulation. Introduction and operation of the transducer gastroscope system are usually well tolerated by the patients, since no mechanical vibrations are generated and there is no need for an oil bag to secure oesophageal wall contact. Cardiac images of high quality are obtained even from structures and regions that are poorly or not at all imaged from external transducer positions.

A high-sensitivity integrated-circuit capacitive pressure transducer

Abstract: A high-sensitivity capacitive pressure transducer with active processing circuit on the chip has been demonstrated and evaluated. The transducer configuration has been optimized by computer-aided design to achieve highest sensitivity for a given maximum dimension. The measured sensitivity of the devices is in the range of 50-150 µV/ V . mmHg, which is approximately one order of magnitude higher than the sensitivity of the piezoresistive pressure transducer of comparable size. Theoretical analysis also shows that a sensitivity on the order of 1000 µV/V . mmHg is also possible using the capacitive approach if the dimension of the device can be enlarged and the full scale pressure range is lowered. Other characteristics of the devices have been investigated and are presented.

Ultrasound tissue probe localization system

Abstract: A novel pulse-echo ultrasound imaging system is disclosed comprising at least three transducers. A first external scanning transducer images a selected scan area of body tissue by pulsing that area with ultrasonic waves. Two additional detector-transducers are disposed at distinct locations on a probe, such as a biopsy needle, which is inserted into the body in the vicinity of the scan area. By determining the sequence of wave front arrivals at the detectors-transducers, the relative location of the probe with respect to the scan area is readily determined and indicated. Either the scanning transducer or the probe may then be maneuvered in response to such indication to ensure that the probe tip is properly positioned relative to the scan area.

Technique for measuring ultrasonic velocity and attenuation spectra in rocks under pressure

Abstract: An ultrasonic pulse technique has been developed for measuring phase velocity and attenuation spectra in rocks inside a pressure vessel. This technique has been adapted from those used in the nondestructive evaluation field. In essence, a broadband acoustic pulse is directed into a lucite buffer, which is followed by the rock sample and another lucite buffer. The pulse partially reflects off both the front and back faces of the sample, and the reflected pulses are received by the transmitting transducer. Digital recording and signal processing techniques are used to analyze the signal. After Fourier transforming each pulse, correcting for diffraction effects, and allowing for partial reflections at the interfaces, the phase shift between pulses at each frequency yields the phase velocity and the amplitude reduction gives the attenuation. Tests on synthetic materials show that as currently implemented, the technique produces reliable measurements at frequencies above 400 kHz. Velocity and attenuation spectra are shown for brine saturated Massilon and Boise sandstones at different effective pressures.

An improved piezoelectric acoustic emission transducer

Abstract: A piezoelectric transducer has been designed and developed that has promise of being a high fidelity acoustic emission (AE) transducer [T. M. Proctor, Jr., J. Acoust. Soc. Am. Suppl. 1 68, S568 (1980)]. Small transducer contact area, elimination of acoustical interference effects associated with certain geometries, and redistribution of the arrival times of reflected signals originating from various elements of the transducer were the guiding criteria in the design. This transducer consists of a conical active element and an extended backing. The transducer’s performance has been compared to a line capacitance transducer using surface wave signals. These comparisons indicate an amplitude response which is flat within ±3 dB for the frequency range of 50 kHz to 1 MHz. The over‐all displacement sensitivity is nominally 2×108 V/m. Factors that influence frequency response such as backing geometry and aperture size have been experimentally investigated and results are reported.

A simple axial displacement gauge for use in the triaxial apparatus

Abstract: The use of electrolytic liquid levels as horizontal inclinometers is described for the measurement of local displacements and strains on laboratory soil samples. The simplicity, accuracy and low-cost of electrolytic levels are said to make such units useful in transducer applications. The liquid level consists of an electrolyte sealed in a glass capsule with three co-planar electrodes partially immersed in the electrolyte. Resistance between the electrodes vary as the capsule is tilted. Inclinometer apparatus described uses an electrolevel for measurement of local torsional strains in soil and it is shown how such a vertical deflection gauge can be used in a triaxial test apparatus for application in routine soil testing. (Author/TRRL)

Technique for measuring ultrasonic velocity and attenuation spectra in rocks under pressure

Abstract: An ultrasonic pulse technique has been developed for measuring phase velocity and attenuation spectra in rocks inside a pressure vessel. This technique has been adapted from those used in the non-destructive evaluation field. In essence, a broadband acoustic pulse is directed into a lucite buffer which is followed by the rock sample and another lucite buffer. The pulse partially reflects off both the front and back faces of the sample and the reflected pulses are received by the transmitting transducer. Digital recording and signal processing techniques are used to analyze the signal. After Fourier transforming each pulse, correcting for diffraction effects and allowing for partial reflections at the interfaces, the phase shift between pulses at each frequency yields the phase velocity and the amplitude reduction gives the attenuation. Tests on synthetic materials show that as currently implemented, the technique produces reliable measurements at frequencies above 400 kHz. Velocity and attenuation spectra are shown for brine saturated Massilon and Boise sandstones at different effective pressures.

Circuit apparatus and method for electrothermal treatment of cancer eye

Abstract: Circuitry for use in a hand-held electronic probe for passing high frequency current through malignant eye tissue of livestock or other tissue such as warts includes a thermistor in a probe tip that contacts the tissue, producing a voltage that controls a voltage controlled oscillator which drives an audio transducer. If, during treatment, the probe tip is held against the malignant tissue with sufficient force, the pitch of a sound emitted by the audio transducer steadily increases, indicating to the user that proper pressure is being maintained to ensure heating of the tissue to the desired treatment temperature. The cicuitry then causes the transducer to emit periodic beeping signals which the user can count to ensure that the tissue is maintained in a desired elevated temperature range for a desired amount of time. Circuitry responsive to the temperature sensor varies the duty cycle of the high frequency current applied to the tissue to maintain the elevated temperature thereof within a predetermined range. Initially, the high frequency current is applied at a substantially reduced duty cycle to prevent excessive temperature lag between the tissue and the probe tip to prevent initial temperature overshoot of the tissue before the thermistor and circuitry can respond to reduce the duty cycle.

Ultrasound diagnosis apparatus

Abstract: An ultrasound diagnosis apparatus comprising, a pulser, a transducer connected to the pulser, which is driven by drive pulses from the pulser to radiate ultrasound wave toward an object and to receive echoes returned from the object to convert the echoes into electrical signals, the thickness of the transducer changing in a direction orthogonal to the ultrasound beam traveling direction, a filter connected to the transducer for filtering the electrical echo signals from the transducer with the filter characteristic which is changed according to a change of the thickness of the transducer, signal processing circuit connected to the filter for processing the electrical echo signals passed through the filter to convert it into tomogram signal, and a monitor connected to the signal processing circuit for displaying a tomogram according to a tomogram signal from the signal processing circuit.

Radiation-induced thermoacoustic imaging

Abstract: The acoustic wave generated by sudden thermal stress is used to obtain information non-invasively on the composition and structure of the stressed body. One or more acoustic transducers (1 and 1') are coupled with the surface of the body to intercept the acoustic wave and generate a corresponding electrical signal. The sudden thermal stress is induced by a pulse of radiation which deposits energy causing a rapid, but very small, rise of temperature. The radiation may be ionizing radiation, such as high energy electrons, photons (X-rays), neutrons, or other charged particles. The radiation may also be non-ionizing radiation, such as RF(2) and microwave electromagnetic radiation (3) and ultrasonic radiation (4). The electrical signal from the acoustic transducer (1) is amplified (5) and supplied to a digitizer (6), which provides a continuous stream of digital words corresponding to samples of the amplified signal. Because in most situations of practical interest the S/N ratio of a single pulse is much less than unity, it is necessary to signal-average the signals from many successive pulses. This is accomplished with a minicomputer or data processor ( 8) suitably interfaced (7) with the digitizer. The resulting data can then be suitably displayed as an image on a CRT display (9) or plotted or numerically printed out.

Telemetering intracranial pressure transducer

Abstract: A telemetering intracranial pressure transducer comprises an airtight casing member housing a pressure-electric transducer for detecting an intracranial pressure, a pressure-receiving layer disposed in contact with the pressure-electric transducer and in pressed engagement with the dura under the skull, and a transmitting circuit for transmitting an output signal indicative of the intracranial pressure through a transmitting antenna. The transmitting circuit includes a telemetering transmission circuit, a microbattery and a switch for switching on and off the microbattery. The transducer thus constructed is entirely embedded below the head, dispensing with external wires or a receiving coil on the head, and detects an intracranial pressure safely and accurately without confining or disturbing the activities of a testee.

Electronic still camera with individual non-volatile memory units

Abstract: An electronic still camera is disclosed having an optical system, a transducer in the form of CCD image sensors for producing image representing signals responsive to an image focused on the sensors by the optical system, an actuable shutter control and circuits in the camera for transmitting image representing signals from the transducer to a recording device having a plurality of individual no-volatile integrated circuit memory units. A controller means in the form of a microprocessor is operated by a shutter control and controls the transmission of image representing signals from the transducer through the circuits to record only a separate single image in each of the individual memory units.

Precision medication dispensing system and method

Abstract: The implantable device includes a medication reservoir, a pulsatile pump and an absolute pressure transducer. The pumping pressure wave developed in the pumping chamber is measured by the absolute pressure transducer whose output is used to adjust the pulsing rate of the solenoid operated pump so that the programmed time averaged rate of infusion of medication into the body is precisely maintained throughout all operating temperature and pressure conditions.

Method and apparatus for reducing repetitive noise entering the ear.

Abstract: Apparatus for improving the audibility of incident sound (4) to a person (3) operating in an environment where there is a substantial background noise field (2) coming from a source (1) of repetitive noise, comprises an adaptable waveform generator (7), a first electro-acoustic transducer (10) receiving a synthesized cancelling waveform from the generator (7) and generating a cancelling noise to at least partly null the background noise, a second electro-acoustic transducer (11) to sense the partially nulled background noise, and adaptor (13) to modify the output of the generator (7) on the basis of the electrical output signal from the second transducer to minimize the nulled background noise, and sensor (5) to feed a triggering signal (6) derived from the source to the waveform generator. The electro-acoustic transducers (10, 11) can be mounted in headset (8) holding the transducers adjacent to an ear of said person without substantially impeding the arrival of said incident sound (4) to said ear.

Ultrasonic transducer coupling member

Abstract: An ultrasonic transducer is improved, particularly for use in perivascular blood flow measurement, by the provision of a coupling member made of a hydrogel The hydrogel is suitably acrylic based; has a water content in the range from 75 to 90% by weight and preferably about 85%; and has acoustic attenuation of less than 2 dBcm -1 at 5 MHz, with longitudinal velocity of sound and acoustic impedance of similar order to those for tissue The crystals of the transducer are preferably sealed from the coupling member by a water resistant coating, the member suitably has an exposed face of part cylindrical shape to accommodate a vascular vessel, and the member is preferably releasably mounted to allow size interchange for different vessels

SENSIM: A simulation program for solid-state pressure sensors

Abstract: A simulation program is described which is capable of calculating the output response of silicon piezoresistive or capacitive pressure sensors as a function of both pressure and temperature. A thermoelastic plane-stress formulation is used in calculating the stress and deflection of the transducer diaphragm. Both analytical and finite-difference solution methods are available, depending on the sensor structure. Diaphragm thickness taper, oxide and package stress, and rim effects are simulated. For capacitive structures, the program accurately predicts the diaphragm deflection and pressure sensitivity as a function of pressure and temperature. Stepped diaphragm structures are shown to be capable of improving pressure sensitivity by as much as 50 percent. The package-induced thermal drift for electrostatically sealed glass-silicon devices is typically less than 0.05 mmHg/°C.

Measurement of velocity of propagation from ultrasonic pulse-echo data

Abstract: A method is proposed for determining velocity of propagation of ultrasound in tissue by processing the pulse-echo data obtained from a compound scan. Individual sectors from different transducer positions are reconstructed and a suitable area common to the two sectors is selected. Cross-correlation of the region of interest is used to detect an apparent shift in the image due to refractive effects. The refractive effects are analysed by a ray-tracing procedure to determine an effective velocity within the tissue. The system has been tested using the U.I. Octoson as input device and both model targets with known velocity of propagation and in vivo liver tissue. The accuracy in the model experiment was +/- 5 ms-1 while the repeatability of measurements in tissue was +/- 15 ms-1. techniques for extending the method to multiple region systems are suggested.

Adaptive misposition correcting method and apparatus for magnetic disk servo system

Abstract: A misposition correction system for correcting misposition errors due to spindle runout and other slowly varying errors in a servo positioning system of a magnetic disk storage device The system includes means for dynamically measuring misposition error with respect to a data track centerline using an anti-aliasing analog filter, means for digitizing the measured analog signal and for removing selected harmonics of the fundamental-frequency of the resulting cyclic error signal, means for transforming the digitized error signal by a matched digital filter whose transfer function contains independently adjustable DC gain, fundamental-frequency gain, and phase lead components thereby to generate a misposition error correction signal that matches the electrical and mechanical response characteristics of the servo system Further, the system includes means to iteratively refine the correction signal by re-applying it to the servo controller when measuring misposition errors with respect to the data track centerline The system stores separate misposition correction signals for each transducer on the disk so that one of several correction signals can be selected depending on which transducer in the device is selected The system further includes means for generating a bias force correction signal to correct for non-linear position errors resulting from variations in bias forces acting on the transducer carriage over its range of radial displacement

Offset-gate chemical-sensitive field-effect transistors (OG-CHEMFETS) with electrolytically-programmable selectivity

Abstract: A selective chemosensitive microelectronic transducer is provided for the detection and measurement of chemical properties, by engineering a field-effect transistor such that source 6 and drain 7 regions are connected to bonding pads 2 and 4, and the semiconductor bulk connected to pad 1. The metal gate 8 is extended laterally to a remote area 9, and also to bonding pad 3 via a narrow metallization track 5 designed to support only a limited, predetermined electrical current in the manner of a fusible link. External electrical access to the device is achieved with wirebonding 14, and the device is selectively sealed with an inert, impervious encapsulation material 10 such that only gate area 9 remains exposed. Electroactive materials are deposited over the offset-gate area 9, or electrodeposited using connection through 8, 5 and 3. Subsequently, link 5 is open-circuited by pulsed electrical overload, creating a floating chemosensitive gate.

Device for the compensation of hearing impairments

Abstract: An exemplary embodiment includes a plurality of parallel signal channels coupled with a signal input transducer, such as a microphone or induction coil. Each of the signal channels includes a respective bandpass filter for selection of a different frequency band, a controlled-gain amplifier, controlled by a volume control potentiometer, circuits for non-linear signal processing, and a bandpass filter for the reduction of distortion components caused by the non-linear processing circuits. A summing amplifier combines the signal components from all channels and is connected via an amplifier to an output signal transducer. Space requirements and power consumption are reduced in such a multi-channel processing arrangement by implementing all of the filters as sampled-data analog circuits. As a result hearing aids are provided which can be worn on the head, e.g. behind the ear.

Matching region for damped piezoelectric ultrasonic apparatus

Abstract: An acoustic impedance match between an ultrasonic transducer and an adjacent transmission medium is obtained, with performance over a relatively wide bandwidth, by providing a special matching region between the transducer and the transmission medium. The matching region includes a layer having a multiplicity of tapered elements. Each of the elements tapers down in size in the direction away from the transducer.

Lever actuator comprising a longitudinal-effect electroexpansive transducer and designed to prevent actuation from degrading the actuator

Abstract: A transducer (51) extended by an electroexpansive longitudinal effect, actuates a lever (77) through a bendable plate (56). Preferably, the plate actuates a first arm (53) having an end which provides the fulcrum. Another bendable plate (79) actuates a second arm (76) having an end which exterts the power to the lever. The plates are symmetrically disposed on both sides of the transducer axis. The lever is differentially actuated by the arms. When such lever actuators are combined into an impact printer head, a guide for printing elements carried by the respective levers are preferably used in preventing the levers from excessively excursing.

Apparatus for disintegrating kidney stones

Abstract: The useful life of the wire probe in an ultrasonic kidney stone disintegration instrument is enhanced and prolonged by attaching the wire (24) of the wire probe to the tip (26) of an ultrasonic transducer (28) by means of a clamping arrangement comprising opposing set screws (60, 65), one (60) of which is adapted to accept the clamping load from the other set screw (65) without deforming the wire by machining a pair of mutually transverse grooves (64) in the inner end face (62) of the screw (60) which is adapted to accept and hold the wire probe along the central longitudinal axis (52) of the transducer tip which is adapted to impart ultrasonic energy to the wire. Additionally, damping material is applied to the wire probe (24) in the form of a damper tube (70) through which the wire probe passes in the region adjacent the transducer tip. The damper tube extends outwardly from the transducer tip (26) a predetermined distance, terminating in a resilient soft rubber joint (72). Also, the damper tube is supported intermediate its length by a support member (82). The damper system thus provided acts to inhibit lateral vibrations of the wire in the region of the transducer tip (26) while providing little or no damping to the linear vibrations imparted to the wire (24) by the transducer (28).

Acoustic flowmeter with envelope midpoint tracking

Abstract: An acoustic burst with a predetermined amplitude envelope is triggered by a square wave signal and transmitted upstream or downstream to a transducer connected to an adaptive control system which tracks the midpoint of the received envelope. The received signal is rectified and fed via a polarity reversing circuit controlled by the square wave to an integrator whose output level controls the frequency of the square wave. The burst transit time is measured to the next zero crossing of the received signal following the half cycle transition point of the square wave.

Apparatus for measuring blood pressure.

Abstract: The open end of a catheter is inserted in the blood vessel of a patient. The catheter is connected by hollow tubing to a physiologic pressure transducer. The tube is filled with an intermediate pressure-transmitting fluid such as a physiologic saline solution. An infusion device between the patient and the transducer constantly flushes the system with a slow flow of fluid. Blood pressure variations are transmitted through the fluid to the transducer, which converts the pressure to electronic information and transmits the information to a monitor for display. Between the infusion device and the transducer is a variable restrictor which damps the pressure waves in the fluid. This restrictor is used to tune the system to eliminate resonant waves, which distort the monitoring reading. In one form, the variable restrictor includes a valve having an orifice, the effective size of which is reduced or enlarged by compressing and releasing a deformable, flexible ring. In another form, the variable restrictor includes a valve which has a valve seat with a flow opening through which the fluid pressure wave passes. To control pressure wave flow through the valve, a valve needle is moved toward and away from a valve seat, which reduces and increases the size of the flow opening.

Digital pressure transducer

Abstract: A digital pressure transducer is formed by mounting a force-sensitive resonator to a structure of nonsymmetrical configuration which produces loads under applied pressure. The frequency of the resonator is measured to provide a digital indication of the applied pressure.