Abstract: A subsea housing assembly, in particular for a subsea sensor, includes a first housing portion and a second housing portion. The first housing portion includes a first electrical connection for data communication and the second housing portion includes a second electrical connection for data communication. A wall provides separation between the first housing portion and the second housing portion of the subsea housing. An inductive coupler, that includes a first coupling section disposed in the first housing portion and a second coupling section disposed in the second housing portion, is provided. The inductive coupler is configured to provide inductive coupling across the wall for providing at least a data communication between the first and second electrical connections.

Abstract: A cochlear implant headpiece, for use with a cochlear implant, including a housing, a diametrically magnetized headpiece magnet, defining an axis and a N-S direction, within the housing and rotatable about the axis, whereby the N-S direction of the headpiece magnet self-aligns with the gravitational direction when the axis is perpendicular to the gravitational direction, and a headpiece antenna associated with the housing.

Abstract: Parallel dipole line (PDL) trap seismometer and vibration sensors are provided. In one aspect of the invention, a seismometer is provided. The seismometer includes: at least one PDL trap having a pair of dipole line magnets, and a diamagnetic object levitating above the dipole line magnets; and a sensing system (passive or active sensing) for determining a position of the diamagnetic object relative to the dipole line magnets and to yield the seismic signal in terms of displacement or acceleration. Methods for sensing vibrations using the present PDL trap seismometer and vibration sensors are also provided.

Abstract: A self-damping geophone, in some embodiments, comprises a housing containing a conductive coil and one or more springs; a first magnet suspended within said housing by the one or more springs, said conductive coil located within a magnetic field of the first magnet; and damping magnets disposed outside of said housing, each of the damping magnets oriented to repel a pole of the first magnet closest to that damping magnet.

Abstract: A nodal geophysical sensing system includes a ground contact sleeve defining an interior space and having at least one feature on an exterior thereof for contacting and compressing ground materials adjacent the exterior. A nodal geophysical sensor having a housing engages at least one feature on the interior space so as to enable acoustic energy transmission between the ground contact sleeve and the housing.

Abstract: An electromagnetic generator includes a magnet assembly having permanent magnets magnetized in a direction of stacking so that surfaces thereof corresponding to the same pole face each other. A solenoid coil is positioned around the magnet assembly so that a position of the solenoid coil relative to the magnet assembly can be changed. Holding parts hold the solenoid coil so that a center of the solenoid coil in a winding axis direction corresponds to a plane position where the surfaces of the permanent magnets corresponding to the same pole face each other at a stop position. Repulsive magnets generate magnetic repulsive forces that maintain the magnet assembly separated from the repulsive magnets. A length of an end face of each permanent magnet in a direction perpendicular to the winding axis direction is equal to or larger than double a length of the permanent magnet in the winding axis direction.

Abstract: This patent deals with methods to selectively excite and analyze the resonance phenomena existing in an enclosed oil, gas and or water reservoir, thereby locating its presence, by doing qualitative and quantitative estimates of its extent via forward modeling. The oil, gas or water reservoir is represented as a fluid filled crack system or as a fluid saturated sponge located in solid rock. This patent covers the actively excited response and details methods to optimize the excitation. Due to interaction between either fluid filled fractures or fluid saturated rock lenses and the surrounding rock, the incident seismic energy is amplified in specific frequency ranges corresponding to the resonance frequencies of such systems. Measurements are made over the survey area, singly or in arrays. These are first used to determine qualitatively the resonance behavior, by relating them to resonance signal sources and possibly their direction. Overall statistical analysis assesses dominant frequencies in the spectrum.

Abstract: Methods and systems utilizing seismic sensors configured or designed for use in seismic signal detection. An electrical current is applied to a seismic sensor such that the moving coil is located at a neutral position relative to the magnetic field in the seismic sensor to compensate for gravitational acceleration.

Abstract: The present invention relates to a system for emitting seismic waves in an underground formation traversed by a well comprising a casing (10). The system comprises a casing seal (1) allowing passage of a magnetic field, an active part generating seismic waves, made up of magnetic-field active elements (4) and arranged outside the casing seal, and a mobile magnetic field induction source (8) arranged inside the casing seal. The invention also relates to a method implementing the seismic wave emission system.

Abstract: An electromagnetic ultrasound transducer is disclosed for receiving linearly polarized horizontal shear waves from an electrically conductive workpiece including a magnetizing unit, which provides a side facing the workpiece, along which a number n of permanent magnets are attached in at least two rows arranged next to one another in such a manner that the magnetic polarities of the magnetic poles which face the side alternate along a row periodically with a period length which corresponds to a trace wavelength ?s and a HF coil arrangement with conductor sections in at least two rows running parallel to one another, through which current can pass in mutually opposite directions.

Abstract: A geophone utilizing an Alnico-9 magnet and having an improved sensitivity over Alnico-9 geophones of prior art through the lengthening of the parasitic air gap between the upper and lower pole pieces which, results in less magnetic flux leakage. The flux concentration through the geophone coils is increased and shifted towards the ends of the magnet. The increase of sensitivity of geophone of the present invention over prior art geophones may exceed 3 dB. The axial length of the coil bobbin is increased, and the positions of the electrical coils are moved towards the ends of the magnet to align with the shifted magnetic flux.

Abstract: A vertical geophone that includes a lower frequency spring, which forms part of the geophone electrical circuit, that is positioned directly on the lower end cap This arrangement eliminates the “spring supported by a spring” arrangement of prior art geophones to minimize geophone distortion and simplify tuning of the frequency springs. A contact spring is positioned between the lower frequency spring and the lower pole piece for forming part of the geophone electrical circuit. One surface of contact spring includes a plurality of wiper surfaces that ensure consistent sliding electrical contact against either the bottom surface of the lower pole piece or the upper surface of the lower frequency spring. The obverse surface of the contact spring is preferably spot welded to the other adjacent member.

Abstract: A geophone utilizing an Alnico-9 magnet and having an improved sensitivity over Alnico-9 geophones of prior art through the lengthening of the parasitic air gap between the upper and lower pole pieces which, results in less magnetic flux leakage. The flux concentration through the geophone coils is increased and shifted towards the ends of the magnet. The increase of sensitivity of geophone of the present invention over prior art geophones may exceed 3 dB. The axial length of the coil bobbin is increased, and the positions of the electrical coils are moved towards the ends of the magnet to align with the shifted magnetic flux.

Abstract: The present invention relates to a system for emitting seismic waves in an underground formation traversed by a well comprising a casing (10). The system comprises a casing seal (1) allowing passage of a magnetic field, an active part generating seismic waves, made up of magnetic-field active elements (4) and arranged outside the casing seal, and a mobile magnetic field induction source (8) arranged inside the casing seal. The invention also relates to a method implementing the seismic wave emission system.

Abstract: A motion sensing transducer is disclosed that includes a case having an inner surface, a first cap that closes the case at a first end and a second cap that closes the case at a second end. The case inner surface, first cap and second cap define a space within the case. The apparatus further includes at least one inner plate member separating the space into at a first compartment and a second compartment within the case, a coil-magnet assembly that produces a signal when subjected to motion, the coil-magnet assembly disposed immediately within the case and in the first compartment, and an electronic circuit disposed within the second compartment that modifies the signal.

Abstract: A sensor assembly includes a seismic sensor element and a shell. The shell at least partially surrounds the sensor element to shield the sensor element from a magnetic field that is generated outside of the shell.

Abstract: The method and the apparatus disclosed serve to acquire seismic induced movements. A coil and a permanent magnet are contained in an enclosure and the seismic movements induce a relative movement between said coil and said magnet. The current induced into the coil is appraised as a measure of said seismic movement. The position of the coil in relation to the permanent magnet is monitored by a position sensor. A closed loop control generates a current that is fed into the coil so that the coil settles at a given neutral position relative to the permanent magnet.

Abstract: A method for compensating the effect of gravity on seismic sensors such as geophones and a gravity effect-free seismic sensor are disclosed. The gravity effect-free seismic sensor of the present invention includes primary sensor (100) operatively responsive to seismic movements and hence generating a seismic signal by having a coil placed in a magnetic field in a first axis of sensitivity (105); an auxiliary sensor (210) operatively responsive to a gravity field for generating a tilt signal, thus provide current to the coil of the primary sensor (100) to induce a force on the coil that at least partially compensates for a weight of the coil, thus ameliorating or eliminating a gravity effect on the primary sensor (100).

Abstract: A mass is levitated with respect to a base, at least one of which is comprised of a diamagnetic material, with the levitated mass also having a permanent magnetic property. A second permanent magnet is optionally configured such that it attracts the levitation mass away from the base to overcome gravitational force on the mass, thereby suspending the mass over the surface of the base. The mass is contained in a nonmagnetic, non-shielding and optionally optically-transparent housing so as to limit its excursion within a range of levitation positions. A position measurement means such as a laser interferometer, capacitance detector, or pickup coil is configured to measure positional deviations of the mass in response to incident pressure wave, the output of which being an electronic signal representing the pressure wave.

Abstract: A mass is levitated with respect to a base at least one of which is comprised of a diamagnetic material, and the levitation mass also having a permanent magnetic property. A second permanent magnet is configured such that it attracts the levitation mass away from said base surface with sufficient magnetic force to overcome gravitational force on the mass, thereby suspending the mass over the surface of the base. The mass is levitated at room temperature, eliminating need for cryogenic mechanisms and materials, and is contained in a nonmagnetic, non-shielding optically-transparent housing so as to limit its excursion within a range of levitation positions. A non-intrusive position or distance measurement means may be optionally configured with the system, such as a laser interferometer, thereby allowing the levitated mass to act as a gravimetric device.

Abstract: The present invention relates to an ultra-broadband hydrophone which has major electronic components and one mechanical component. The first electronic component comprises a flux-gate magnetometer for sensing changes in an ambient magnetic field and for creating an electrical signal representative of the ambient magnetic field. The second electronic component comprises an electrical circuit for demodulating the electrical signal and a low pass filter for smoothing the demodulated signal. The mechanical component is a magnetic diaphragm for receiving acoustic pressure waves and for causing changes in the ambient magnetic field in response to the received acoustic pressure waves. In a preferred embodiment, the hydrophone of the present invention also includes a sub-Hertz differential magnetic field winding for generating a differential magnetic field which nulls the ambient magnetic field about the flux-gate magnetometer.

Abstract: A method and apparatus for sensing one or more physical parameters, including acoustic waves having frequencies from approximately 0 Hz to 15 Hz, electromagnetic waves having frequencies from approximately 0 Hz through 35 Hz and seismic waves having frequencies from approximately 0 Hz through 15 Hz, and detecting precursor seismic activity indicated therein. Acoustic waves are sensed using an infrasonic transducer that produces an electrical signal representative of such waves. Electromagnetic waves are sensed using a suitable antenna, the antenna preferably comprising AC power lines. The antenna produces an electrical signal representative of such waves. Seismic waves are sensed using an accelerometer that produces an electrical signal representative of such waves.

Abstract: The objective of this invention is to simplify and provide a versatile device capable of accurately measuring seismic activity. The technique is based on magnetic levitation. The concept of magnetic levitation has been around since the 1960's, and it has been used extensively for high speed trains, however its use in seismology has been described in U.S. Pat No. 3,626,364 issued to Simon et al. However the present invention utilizes a four-vector magnetic field instead of three separate scalar magnetic fields. The advantages of present approach is reduction of three seismic masses to a single seismic mass.To detect seismic activity using this concept, a seismic mass must be magnetically suspended. A seismic mass trapped in a magnetic field still possesses its inertia. Therefore, as the magnetic field moves under the influence of seismic activity, the seismic mass will tend to stay in the same place. The controller, however tends to keep the seismic mass in its place.

Abstract: An electroacoustic transducer having a diaphragm and a magnetic driving portion respectively housed in a housing wherein the magnetic driving portion vibrates the diaphragm magnetically in response to an electric signal. A base member for closing an opening at the rear side of the housing is formed of a metallic plate. Lead portions are provided by extending both ends of a coil of the magnetic driving portion. Terminal patterns are formed on a surface of the base member with an insulating film between them. The lead portions of the coil of the magnetic drive portion are connected to the terminal patterns.

Abstract: An apparatus for generating acoustic pressure pulses in an acoustic medium has a membrane that can be driven which adjoins the acoustic medium and which is driven in an impact-producing manner. The membrane is mechanically pre-stressed so that it returns into its initial position after a pressure pulse is generated.

Abstract: A flexural transducer includes a hollow tube that is magnetically driven by a coil/magnet assembly. A magnetic field is provided by passing a current through the coil. The filed passes through an air gap between the coil and the magnet to attract and repel the magnet during alternating portions of the current's cycle. The magnetic transducer driver mechanism permits high drive capability, high temperature operation and provides lower frequency operation than conventional ceramic drivers.

Abstract: An acoustic transducer provides an elongated outer shell made of magnetic material and having a pair of flexural members attached to each other in the elongated direction and having a flexural portion extending normally to the elongated direction and forming a partial enclosure between the two flexural portions, and a magnetic drive located within the partial enclosure and engaging the flexural portions for causing the portions to oscillate flexurally.

Abstract: A geophone system for measuring mechanical vibrations such as seismic waves include a mechanical transducer with an electronic processing circuit. The mechanical transducer includes an inertial mass adapted to be excited by an input acceleration signal and by a force transducer. The excitation is detected by a sensor element and the processing circuits of the geophones control the force transducer and are connected with a central station via a transmission line.

Abstract: An underwater acoustic projector including a Class IV flextension shell, preferably in the form of an ellipsoid, is connected to and driven by two substantially identical electromagnets having mutually opposing pole faces and having a common spatially uniform air gap which is centered between the pole faces. The coils of the two electromagnets are connected in series and when excited by a controlled current, generate a mutually attractive variable reluctance force which causes the pole faces to be attracted toward one another. The shell secured to the electromagnets elastically flexes along one of two mutually perpendicular axes resulting in a volumetric displacement of the outer surface of the shell.

Abstract: A geophone is disclosed that has a cylindrical housing closed at one end by a bottom and at the other end by a top. A magnet assembly and a coil-mass are located in the housing. Springs support the coil-mass for axial movement relative to the magnet assembly along the longitudinal axis of the housing. A pair of coil terminals are mounted in the upper end of the coil-mass adjacent the top of the housing. A pair of eyelets extend through the top of the housing and outside geophone terminals are attached to and extend through the eyelets into the housing. A pair of pigtails connect the geophone terminals to the coil terminals.

Abstract: A noise cancelling watertight transducer that converts sound wave to electromagnetic waves or conversely electromagnetic waves to sound waves comprises a hollow shell having curved walls mounted for movement in a resilient container. A freely movable inertial mass is located inside said shell. The inertial mass resists movement when a force is applied thereto. Signal translating means are incorporated therein consisting of either an electromagnetic device, a piezoelectric element or voltage potential senative element that is mounted in and connected with said shell and interacts with said inertial element. In response to appropriate signal some embodiments of the instant invention acts as a bidirectional device converting electrical signal to acoustical signal or conversely acoustical signal to electrical signal.

Abstract: A detector for detecting the acceleration, the velocity or the displacement of a point is described. The detector includes a light source, at least two photoelectric elements spaced apart from each other over a predetermined distance and a focusing optical system disposed between the light source and the photoelectric elements; the combination being particularly suited for use as an optical seismic detector for detecting and mapping an underground stratum structure.

Abstract: A self-orienting, directionally sensitive particle velocity transducer with an axially magnetized magnet which, displaced by gravity, floats off-center in a chamber filled with ferromagnetic fluid. Wire coils affixed coaxially to the chamber ends asymmetrically intersect the magnet's flux lines. Axial chamber rotation results in gravitationally induced sideways movement of the magnet to maintain its equilibrium position. An impinging sound wave causes relative movement between the low inertia chamber-coil assembly and the high inertia magnet, thereby inducing a voltage in the coils--a relatively high voltage for vertical movement due to vertical assymetry, but a relatively low voltage for horizontal movement due to horizontal symmetry. Axial sensitivity is low because the ferromagnetic fluid filling the narrow gap between the magnet and the chamber ends resists relative axial movement and any induced voltages in the coils cancel.

Abstract: A rotational geophone is provided. This rotational geophone employs a coil mounted on a torsional wire in a static magnetic field to detect movement of the frame relative to the coil. This rotational geophone may also be combined with a velocity geophone to obtain seismic data representing shear waves traveling in a particular direction.

Abstract: An improved geophone for seismic prospecting is disclosed which features plural magnets of varying mass oscillating with varying frequencies within one or plural coils whereby the frequency response of the geophone may be optimized.

Abstract: A magnetically suspended magnetic transducer has a first magnetic assembly including a first magnetizable housing with a bottom and upstanding walls defining an interior volume, a pair of opposed, mutually spaced magnets with a pole piece in between, and a coil in the interior volume in flux cutting relationship with the additive magnetic fields generated by the magnetic pair. The second assembly is magnetically suspended above the first assembly and includes a second housing with a closed top and downwardly depending side walls partially surrounding the side walls of the first housing, an additional magnet secured to the inner top surface in opposing magnetic relation to the closest one of the pair of magnets in the first assembly so that the magnetic forces urge the second housing away from the first. A mass secured within the second housing provides a weight of sufficient magnitude to counteract the magnetic force of repulsion tending to separate the two assemblies.

Abstract: Transducer for converting mechanical vibrations into corresponding electrical signals. Two separate coils are disposed in permanent magnetic fields produced by a magnet assembly. The coils on the one hand and the magnetic assembly on the other are mounted for movement relative to each other. The magnet assembly is structured and disposed relative to said two coils respectively so as to reduce the electromagnetic coupling between the two coils to zero, while having an electromagnetic coupling only between a respective one of said coils and said magnet assembly. In a composite seismometer comprising a transducer of the above-described type and an amplifier, one of said coils is connected to the amplifier input, while the other one of said coils is included in a feedback circuit for said amplifier.

Abstract: A robust air gun fire time sensor consists of a housing to which is secured a protruding nonmagnetic internal barrel having a bore. The bore is closed at one end by a magnetic end cap defining an air chamber and the bore is in fluid communication with the firing chamber of an air gun. A generator coil surrounds the barrel. A bar magnet is floatingly mounted inside the bore and is urged against a shoulder formed in the end cap. When the air gun is charged with compressed air, some of the air becomes entrapped in the air chamber. When the air gun is fired, the entrapped compressed air in the air chamber pushes the bar magnet away from the shoulder. The collapsing magnetic field creates a transient electric pulse in the generator coil.

Abstract: A variable reluctance type firing sensor is mounted on an air gun for providing an electrical signal indicative of the instant of firing of the air gun. The firing sensor has a magnetic circuit which includes a permanent magnet, a pair of pole pieces and an armature including magnetically permeable material and which is free of mechanical restraint in its normal operating position, being held by magnetic attraction in position in the magnetic circuit. The armature freely "floats" on its "magnetic springs" within a thin walled chamber in which it is housed between the pole pieces, assuming a predetermined position of least magnetic reluctance. The armature which is acceleration-responsive is suddenly displaced from its predetermined position upon the firing of the air gun, and thus the reluctance of the magnetic circuit abruptly increases at the instant of firing.

Abstract: A combination seismic/magnetic transducer capable of detecting movement in a magnetically-permeable body or vibration within the body while it is stopped.

Abstract: The damping of transducers having a mass oscillating in the manner of a piston in a cylinder containing damping fluid on both sides of the cylinder is rendered adjustable by the provision of a conduit through the mass for the flow of damping fluid from and to either side of the oscillating mass. An adjustable valve is preferably provided in a part of that conduit for damping control through regulation of damping fluid flow.