Showing papers on "Transducer published in 1974"

Implantable pressure transducer

Abstract: A wireless, surgically implantable pressure transducer for measuring pressure of fluid or tissue in a body chamber such as brain ventricle of a patient suffering hydrocephalus or a severe head injury. The transducer includes a coaxial variable capacitor electrically connected across an inductor to form a parallel resonant L-C circuit. Alternatively, a coaxially variable inductor may be connected across a capacitor to form the L-C circuit. A bellows is mechanically connected to the variable component to vary the value of capacitance or inductance and hence the resonant frequency of the L-C circuit in response to pressure changes of the fluid in which the bellows is immersed. The transducer is electromagnetically coupled to an external source of variable-frequency oscillatory energy such as a grid-dip oscillator which enables external detection of the transducer resonant frequency which is in turn indicative of the level of fluid pressure being sensed.

A Sector Scanner for Real Time Two-Dimensional Echocardiography

Abstract: During the past several years one-dimensional pulse-echo ultrasound techniques have proven extremely useful in cardiac diagnosis. A one-dimensional system, however, only visualizes structures lying along a single straight line. The spatial relationships of the various cardiac structures are therefore not so easily defined as with two-dimensional systems which display the heart by constructing a plane image composed of many straight lines. We have developed a sector scanning system for obtaining two-dimensional echocardiograms in real time using ultrasonic pulse-echo techniques. Images are produced by angling rapidly a single transducer through a 30-degree sector from a fixed spot (between ribs) on the patient's chest. Thirty complete sectors (or frames) are produced per second. The use of a large diameter transducer ensures that signal strength is good and cardiac structures, including endocardium, can be visualized. Other advantages include high transducer sensitivity, real time imaging and easy visualiz...

Acoustic emission: some applications of Lamb’s problem

Abstract: A method for obtaining the signatures (waveforms) of certain acoustic emission events has been developed. The waveform is that at the source, free of contamination by ringing of the specimen, apparatus, and transducer. The technique is based on the comparison of two signals at the transducer, one from the event in question and one from an artificial event of known waveform. The apparatus is also adapted to the calibration of transducers in a certain sense. The configurations of source (real or simulated acoustic−emission event) and receiving transducer correspond to those of some special cases of Lamb’s problem. As a byproduct, the results may be of some interest to seismologists.Subject Classification: 40.42; 35.54, 35.80, 35.68; 40.50; 85.44.

Development and application of new equipment for transrectal ultrasonography

Abstract: We have successfully developed a new type of equipment for transrectal ultrasonography. The equipment consists of three parts: a transducer assembly, a radial scanner, and a chair. The specially designed transrectal transducer assembly consists of a double tube system; a concave oscillating disc is attached to the rotative inner tube. The top of the transducer tube is covered with a water-filled rubber balloon which is kept in contact with the rectal wall. The chair has a hole over which the anus is positioned and the tube with the radial scanner is introduced into the rectum from below. The angle of the. projecting transducer tube can be shifted freely with a lever. The depth of insertion of the transducer is controlled by the scanner handle. This “sitting posture” procedure has several advantages over the lithotomy position. The diagnostic application of this method is described for examination of different intrapelvic organs such as the prostate, the urinary bladder and the uterus.

Method of transmitting ultrasonic impulses to surface using transducer coupling agent

Abstract: Gel compositions are disclosed containing a primary thickening agent (e.g. carboxy polymethylene polymer) combined with small but effective amounts of an auxiliary hydroxy-containing thickener, e.g. an hydroxy alkyl cellulose polymer. The gel is particularly suitable for use with transducers wherein the gel is introduced between a transducer element (for example, an electrode) and skin or surface. The gel compositions are advantageous in that they do not irritate the skin, do not corrode the transducer element, are slow to dry and do not substantially leak out from the area of contact. The process of using the gel is also included.

Vibrational response of sonar transducers using piezoelectric finite elements

Abstract: The finite element method is applied to the vibrational analysis of electromechanical sonar transducers of arbitrary geometry Three‐dimensional hexahedral finite elements which include the effects of piezoelectric coupling are formulated, and the solution of the resulting coupled electroelastic equations of motion is presented The vibrational response of a particular transducer element is computed, and comparisons with experimental mesurements are made The calculated deformations of the transducer are presented in the form of computer generated displays A data reduction scheme is also utilized to clarify the physical meaning of the transducer response

Focused arc beam transducer-reflector

Abstract: An acoustic transducer-reflector using a single disc-shaped piezoceramic element radiating into a compound reflector for obtaining a line focus sound beam that is characteristic of focused-arc transducers that maybe used for underseas applications and for non-destructive materials testing. The single transducer emits acoustic energy into the compound reflector which reshapes a circular beam into a focused arc beam. A shadow mask or aperture stop positioned in front of the reflector assures a beam such as would be radiated from a ring source.

Surge detector for turbine engines

Abstract: A pair of pressure transducers are connected to pressure probes positioned in a flow passage of a turbofan engine downstream of the fan and respond to pressure fluctuations which occur in the airstream. One transducer has a high response capability, and its output is passed through a band-pass filter to isolate the high frequencies of interest. The other transducer has a low response capability, and its output is passed through a low-pass filter to provide the steady state pressure level. A triggering level is scheduled as a function of the steady state pressure level, and a comparator is used to continuously compare the triggering level with the level of the high frequency pressure signal produced in the band-pass filter. If the amplitude of the high frequency pressure is greater than that of the triggering level, the engine is approaching a surge or stall condition, and a warning signal is generated which may be used to institute corrective action.

Tabulation of some integral functions describing diffraction effects in the ultrasonic field of a circular piston source

Abstract: Values of some integrals occuring in the theory of diffraction effects were computed and used to calculate the average phase and average relative amplitude of the acoustic pressure experienced by a circular receiver coaxial with a circular piston transducer of the same radius. Tables of the results are described.

Acoustic surface wave resonator devices

Abstract: This disclosure concerns acoustic surface wave resonator devices having particular applicability as bandpass filters and oscillator frequency control elements at VHF and UHF frequency ranges. In a basic form of the acoustic surface wave resonator device, first and second grating structures are arranged in spaced aligned relationship on a substrate of piezoelectric material with an interdigitated acoustic surface wave transducer interposed therebetween. The grating structures provide plural edge reflectors on opposite sides of the surface wave transducer and are so positioned in relation thereto to set up a standing wave resonance condition with a controlled bandwidth from the reflection of acoustic signals generated by the transducer. In another form, input and output acoustic surface wave transducers are interposed between first and second grating structures, wherein the output transducer couples electrical energy out of the resonator device. Either acoustic or electrical coupling may also be introduced between the input and output transducers to further improve signal transmission.

Transducer positioning system

Abstract: A transducer positioning system is disclosed wherein a transducer is positioned over a magnetic disc by sensing previously recorded information. The information consists of separately identifiable magnetic recordings occurring on adjacent tracks of a disc surface. The information is sensed by a servo transducer which produces a servo signal containing responses to each identifiable magnetic recording. A transducer position is defined when the signal strength of each of the responses is exactly equal.

Acousto-optic modulation device

Abstract: An acousto-optic modulation device is provided which is comprised of an interaction material of an injection moulded plastic integrally combined with a transducer which is bonded automatically to the interaction material during the injection process. A beam of light is projected through the interaction material, the light being diffracted by an acoustic field established by the transducer.

Ultrasonic acoustic pulse echo ranging system

Abstract: An ultrasonic acoustic pulse echo ranging system for monitoring the depth of liquid in a tank has transmitter and receiver transducers for mounting side-by-side in an upwardly directed disposition and exposed to the liquid at a datum level. A transmitter and receiver are adapted for coupling to the transducers from outside the tank. The transmitter includes an ultrasonic frequency oscillator for energizing the transmitter transducer to transmit acoustic pulses of the ultrasonic frequency, a gate to start the oscillator, a continuously cycling counter coupled with and effective to actuate the gate to start the oscillator at the start of each counting cycle, a regulator to stop the oscillator to determine the length of each transmitted acoustic pulse in terms of the number of cycles of the ultrasonic frequency in the pulse. The receiver is arranged to detect outputs from the receiver transducer and to generate output pulses in response to echoes of the acoustic pulses from the free surface of the liquid. A display device, and latching means responsive to the output pulse of the receiver to connect the counter to the display device to display a measure of the time interval between the transmission of an acoustic pulse and the detection of its echo. The regulator includes a regulating counter of the ultrasonic cycles which is resettable at zero by the stopping of the oscillator, and a count comparator, which is coupled to the latching means, to determine that the regulator is responsive to variations between successive measured time intervals to regulate in the sense of the variations, the length of the next transmitted pulse.

Two applications for a dual-beam transducer in hydroacoustic fish assessment systems

Abstract: This paper describes the advantages of using a narrow- and a wide-beam acoustic transducer in systems for estimating fish abundance. In the technique considered, the acoustic pulse is transmitted with a narrow beam and the echo is received on both the narrow and wide beams. The signals received at the two transducers can be used to determine the acoustic scattering cross section of the fish. The mean value of the acoustic scattering cross section can be used to evaluate the scale factor needed by echo integrators to obtain an absolute abundance estimate. The outputs of the two transducers can also be used to control the sampling volume in an echo counting system.

Analysis and correction of pressure wave distortion in fluid-filled catheter systems.

Abstract: Dynamic characteristics of a variety of catheters and their dependence on various operating parameters are presented. Careful flushing of the catheter with degassed water or saline considerably improves the performance of these systems. The operating temperature, number of catheter uses, and average transmural pressure difference do not have a significant effect. The error due to catheter distortion in commonly used left ventricular performance indices (end diastolic pressure, peak systolic pressure, maximum dp/dt and Vmax) was assessed. On the basis of these results, it is shown that the natural frequency of the catheter system must be greater than 40 Hz to produce results accurate to 10%. The experimental data were used to develop a semi-empirical model for the catheter transducer system. This model was used in the design of an analog compensator to further improve the dynamic characteristics of the catheter transducer system. The compensator requires only two parameter settings, catheter natural freque...

Ultrasonic transducer probe system

Abstract: An ultrasonic transducer system comprises a one or two dimensional array of transducers which are subdivided into groups. The groups are selected and operated simultaneously in a manner to produce acoustic energy beams which provide an interference pattern in the near-field focal zone. The groups, moreover, are shifted incrementally along a predetermined direction to provide a scan along a workpiece surface. The transducer system, operating in a manner similar to a Fresnel zone lens, yields greatly improved image resolution, particularly when used in conjunction with a B- or C-scan presentation.

Thin-film integrated circuit with tank circuit characteristics and applications to thin-film filters and oscillators

Abstract: A thin-film integrated circuit with tank circuit characteristics may comprise a surface acoustic wave transducer with appropriate geometry. A preferred embodiment of such integrated circuit includes, in addition to the surface acoustic wave transducer, surface acoustic wave reflecting means located adjacent the transducer, and preferably on opposite sides thereof. The reflecting means may include a pair of reflectors and be proportioned so that the device exhibits a single resonant-anti-resonant frequency pair, such as a single tank circuit. Alternatively, the reflectors may be proportioned such that the device exhibits multiple resonant-anti-resonant frequency pairs. The operating frequency may be as high as hundreds of megahertz to one gigahertz. Applications of the thin-film integrated circuit to thin-film filters and oscillators are also disclosed. In addition a novel form of surface acoustic wave transducer is disclosed which exhibits lower equivalent capacitance than do prior art surface acoustic wave transducers.

Intrusion detection systems

Abstract: A system for sensing seismic and magnetic disturbances, comprising a segmented transducer, such as a line sensor, and electronic circuitry for processing the signals developed by the segmented transducer. The segmented transducer comprises sets of windings wrapped around a ferromagnetic core. Currents are induced in the transducer windings by magnetic field disturbances caused by external ferrous objects. Electronic signal processing circuitry associated with the transducer extracts information from the induced seismic and magnetic signals and activates an alarm if the information meets predetermined criteria. Important criteria used include whether the seismic signals are impulsive, whether the magnetic or stress disturbances are localized, and whether specific thresholds of magnetic and stress activity are reached.

Grain loss monitor

Abstract: A grain loss monitor for a combine harvester derives a grain loss rate signal in accordance with the number of grains impinging on a transducer and a ground speed signal proportional to the ground speed of the combine and divides the former by the latter to derive an analog of grain loss per unit area which is independent of time. The preferred embodiment includes a one-shot multivibrator which is triggered to its unstable state to generate a fixed width pulse each time a grain kernel strikes the transducer, a tachometer coupled to the combine wheels and a period timed integrator triggered by tachometer pulses for deriving a unidirectional ground speed voltage inversely proportional to frequency of the tachometer pulses, a pulse frequency modulation chopper circuit turned on and off by the fixed width one-shot pulses and having its peak voltage controlled by the unidirectional ground speed signal for accomplishing division of grain loss rate by combine ground speed, and an averaging circuit for determining the average voltage of the chopper output pulses as an analog of grain loss per unit area.

Automatic frequency control for a sandwich transducer using voltage feedback

Abstract: An automatic drive control circuit for energizing or driving a sandwich transducer, which includes a mechanical displacement amplifier, piezoelectric crystal drivers and feedback piezoelectric crystals, compares the feedback voltage proportional to displacement and the driving voltage. The frequency of such driving voltage is automatically adjusted to drive the sandwich transducer at mechanical resonance, which occurs when the feedback voltage equals or exceeds the driving voltage. The drive control includes a sweep circuit coupled to a variable frequency oscillator, which produces an AC square wave signal at a frequency dependent on the sweep signal, and the AC signal is amplified and provided as the driving signal to the sandwich transducer. A comparator compares the driving voltage with the feedback voltage, and when the latter equals or exceeds the former, the sweep circuit locks at a fixed voltage to lock the oscillator AC signal frequency, which is maintained constant while the sandwich transducer is maintained at mechanical resonance.

Measurement of magnetostriction and vibration with regard to transformer noise

Abstract: A simple technique of measuring the dynamic magnetostriction in silicon-iron using displacement transducers is discussed. The importance of stress and harmonics of magnetostriction is shown by considering the effects of improving the stress sensitivity of steel and reducing core vibration by a suitable bonding technique which can also reduce transformer noise.

Transducer arrangement for ultrasonic rail tester coupling carriages

Abstract: A transducer arrangement for ultrasonic rail tester coupling carriages comprising a first pair of flat angle signal transducers that are both connected to be senders and receivers and are directed in opposite directions lengthwise forwardly and rearwardly of the rail along the center of the rail head, a second pair of flat angle signal transducers that are both connected to be senders and receivers and are directly forwardly and rearwardly of the rail but are canted toward the rail gauge edge at an angle of 19°, and a third pair of flat angle signal transducers, one of which is a sender and the other of which is a receiver, that are canted in opposite directions toward the rail gauge edge at an angle of 80 degrees to provide a zig-zag signal path of multiple bounces across the rail head. The transducers act through transmitting wedges made of a material to be inefficient as a medium through which ultrasonic sound may be sent such that a significantly improved signal to noise ratio results.

Method and apparatus for continuously monitoring systolic blood pressure

Abstract: The invention relates to a method and apparatus for continuously monitoring systolic blood pressure of a subject. The instrument includes a light transducer for detecting variations in light intensity corresponding to variations in blood volume of tissue of the subject under the transducer and for converting the changes in light intensity to changes in voltage. In one embodiment, a heater is provided to dilate the tissue under the transducer. The voltage signals are differentiated with respect to time, and the differentiated signal is sampled once every heart beat of the subject at the beginning of diastole, or at the maximum value of the differentiated signal sampled during diastole, to produce a sampled voltage signal. To this sampled voltage signal is added a voltage representative of a steady pressure, and the sum is a voltage representative of systolic pressure. The amplitude of the steady pressure is a function of blood pressure in the aorta and large arteries of the subject, stiffness of the aorta and large arteries, and the total peripheral resistance of the subject.

Optical fiber deflection device

Abstract: An optical fiber deflection device is described in which an electrical transducer is used for deflecting the fiber in response to an electrical control signal in order to deflect a light beam transmitted through such fiber. The transducer includes a nonmagnetic deflector means attached to the fiber and connected to an electrical current source, for deflection of the fiber by movement of the deflector means. In one embodiment employing an electromagnetic transducer, an electrical conductor is attached along the length of the fiber and is connected to a D.C. current source to produce a magnetic field around the conductor so that they may be deflected by pairs of electromagnetic coils positioned adjacent the side of the conductor when a control signal is applied to such coils. Alternatively, the control signal can be applied to the conductor attached to the optical fiber and a D.C. current caused to flow through the electromagnetic coils. Other embodiments of the invention use a piezoelectric transducer means including a piezoelectric element attached to the optical fiber so that they are deflected in response to a control signal applied to such element. In still another embodiment of the invention, the electromagnetic transducer means includes electromagnetic coils provided around a pair of magnetostrictive wires each having one end fixed and their other ends attached to the fiber, so that such wires expand and contract to deflect the fiber when a control signal is applied to such coils. In a further embodiment, a thermoelectric transducer means is used including a thermal expansion element, such as a bimetal strip, attached to the fiber and an electrical heating element supported adjacent to such expansion member so that when a control signal is applied to such heating element, the expansion member bends an amount corresponding to the current of such signal to deflect the fiber.

Replaceable element ultrasonic flowmeter transducer

Abstract: An electroacoustic ultrasonic transducer is described which is usable under high pressure and high temperature operating conditions, and is readily replaceable. A piezoelectric transducer element is disposed within a metallic housing and coupled to a metallic acoustic window which is exposed to the sensed acoustic medium, with very efficient acoustic coupling between the piezoelectric element, the acoustic window, and a damping block disposed behind the piezoelectric element.

Contribution to the interferometric measurement of sub‐angstrom vibrations

Abstract: A Michelson interferometer is described for the measurement of low‐frequency vibrational amplitudes in the sub‐angstrom range (down to 10−3 A) as a function of temperature. For this purpose a temperature stabilizing circuit has been developed. The use of a condensor microphone as an electromechanical feedback transducer opens up the possibility to relate the amplitude measurements to the wavelength of light. By these means the accuracy, reliability, and versatility of the interferometer are considerably improved and the draw‐backs of existing set ups are effectively eliminated.

Acoustic Fresnel zone plate transducers

Abstract: Experimental focal plane intensity distributions are presented for a 10‐zone acoustic zone plate operating at approximately 10 MHz. The results are related to the spatial frequency response of the transducer. Some initial imaging experiments with this transducer are described along with preliminary results for an acoustic phase plate.

Ultrasonic wave generator

Abstract: The ultrasonic wave generator of the present invention always drives a transducer with the resonant frequency f o of the transducer. Although the resonant frequency f o changes due to the temperature change etc., the driving frequency automatically follows the change of the resonant frequency f o . The control of the driving frequency is performed by means of a feed-back loop including a voltage controlled oscillator and means for applying a control signal to said voltage controlled oscillator according to the amplitude and/or phase of the driving signal of the transducer.

Ultrasonic imaging apparatus for three-dimensional image display

Abstract: An improved ultrasonic imaging apparatus utilizing ultrasonic waves for obtaining an image of a target object which comprises a transmitting transducer radiating ultrasonic waves whose direction of radiation varies depending on the input frequency, a receiving transducer receiving reflected acoustic waves from a target plane, a frequency analyzer converting the output signal of the receiving transducer into a signal representing the position of the target plane on the basis of the frequency and the position of the received acoustic waves on the receiving transducer, and an image display unit displaying the output signal of the frequency analyzer. In the apparatus, in order to obtain a three-dimensional image including depthwise image information in addition to plane image information of the target object, the frequency analyzer is constructed so that a plurality of image information successively obtained from a plurality of target planes of different depths can be converted into signals representative of different depths to be displayed in superposed relation on the display unit.

Automatically calibrated respiratory ventilation monitor

Abstract: A respiratory ventilation monitor having a flow sensing transducer including a thermistor connected in a bridge circuit for providing a signal indicative of air flow across the thermistor. The output of the bridge circuit is connected to a differential amplifier for controlling a current source to maintain the bridge in a balanced condition. Changes in current supplied to the bridge circuit are detected and applied to a second differential amplifier having an exhalation signal output corresponding in time and magnitude with the quantity of air being exhaled by a patient being monitored. An automatic calibration system is provided to control the zero level of the exhalation signal and such system includes a feedback circuit connected between the signal output and input terminals of the differential amplifier so that manual calibration is unecessary for overcoming small variations in ambient conditions.