65 results about "Magnetic field amplitude" patented technology

A method for controlled source electromagnetic Earth surveying includes deploying a plurality of electromagnetic sensors in a selected pattern at the top of an area of the Earth's subsurface to be surveyed. At least one of a transient electric field and a transient magnetic field is applied to the Earth in the vicinity of the sensors at a plurality of different positions. At least one of electric field amplitude and magnetic field amplitude at each of the sensors is recorded each time the transient electric field and / or magnetic field is applied. Each recording is adjusted for acquisition geometry. An image is generated corresponding to at least one sensor position using at least two stacked, adjusted recordings.

A system providing an inductive power and data link between an external transmitter and miniature internal receiver is presented. The system is suited to applications where the receiver must be of a small size and the system must consume very little power, such as an implanted biomedical device. The system is also compatible with systems where bi-directional communications are required. The novel transmitter and receiver form an improved forward data telemetry system. The transmitter consists of a Class-E converter with its optimum operating frequency being synchronously, instantaneously and efficiently altered in accordance with the data to be transmitted, thereby producing an FSK modulated magnetic field of substantially constant amplitude. The constant amplitude output allows for the continuous, data-independent transfer of power to the miniature receiver and its associated electronics. The present invention also represents an improvement over the high efficiency Class-E converters previously patented by the inventors. The receiver consists of a coil and an integrated rectifying system to recover operating power from the incident magnetic field, as well as an FSK demodulator whose operation is based on the multiphase comparison of charging times of integrated capacitors. The described FSK demodulator approach removes deleterious effects resulting from low-frequency changes in the transmitter frequency, and eliminates time distortion artifacts generated by circuit imbalances and asymmetries in the power recovery process. The combination of the transmitter and receiver improvements yields a reliable data transfer system unaffected by circuit imbalances and incidental variations in the amplitude and frequency of the magnetic field.

A near field RF communicator has an inductive coupler (10) to enable inductive coupling with a magnetic field of an RF signal. A demodulator (102) extracts modulation from an inductively coupled magnetic field. A power provider (109) provides a first power supply for the communicator independent of any inductively coupled signal while a power deriver derives a second power supply from an RF signal inductively coupled to the antenna. A regulator (206; 1302) regulates a voltage supplied by at least one of the first and second power supplies on the basis of a comparison with a reference voltage. A modulator (M) is provided to modulate an inductively coupled magnetic field with data to be communicated via the inductive coupling. In an example, a regulator controller is provided to prevent operation of the regulator in the event of a magnetic field amplitude below a predetermined level or the presence of modulation.

A noninvasive method and apparatus for treating living tissue with pulsed electromagnetic fields (PEMFs) having selectively reduced high-frequency signal components, with improved bioresponse provided by magnetic field amplitudes less than approximately 40 μT, and most preferably in the range of 4–10 μT. Such amplitude levels for the disclosed PEMF signal are particularly effective with a treatment duration in the range of 0.25–2 hours / day.

A method for determining the location of an underground sonde transmitter is disclosed. In some embodiments, the method includes measuring a set of complex electromagnetic field magnitude and phase strengths at one or more of positions while traversing a target sonde path at any angle using one or more electromagnetic coil sensors, modeling a set of expected complex electromagnetic strengths of a hypothetical sonde at the one or more of positions for one or more of the electromagnetic coil sensors, the set of expected electromagnetic field values corresponding to a model for the target sonde, and estimating parameters related to the target sonde based on the residual error between the measured set of complex electromagnetic field values and the modeled set of expected complex electromagnetic field strengths, wherein a final estimated parameter set is determined after the residual error has converged to a minimum tolerance.

A magnetic field measurement system for measurement of weak magnetic field signals or a wearable assembly includes at least one magnetometer and a shield disposed around the magnetometer. The shield includes a first portion configured for positioning between the at least one magnetometer and a source of the weak magnetic field signals. The first portion is made of an amplitude-selective magnetic shield (ASMS) that preferentially passes magnetic fields having a magnetic field amplitude below a threshold (for example, 500 nT or less) and shields magnetic fields having a larger magnetic field amplitude.

A method for determining the location of underground cables and pipes is disclosed. In some embodiments, the method includes measuring a set of electromagnetic field magnitudes and phases at a plurality of positions while traversing a target line parallelly using 3D electromagnetic coil sensors, the 3D electromagnetic coil sensors being orthogonally oriented to the target line, modeling a set of expected complex electromagnetic field magnitudes of a single underground conductor at each of the positions to form a set of values corresponding to a set of individual models for the target line, determining which of the set of individuals models is a best model, determining confidence information at each of the positions based on a comparison between the measured set of complex electromagnetic magnitudes and phases and the best model, and determining parameters at each of positions related to the target line from the best model.

A power generation type AC magnetic field sensor based on magneto piezoelectric effect is a laminated structure consisting of magnetostrictive rod, a piezoelectric material, the magnetostrictive rod and a permanent magnetic material; the upper surface and the lower surface of the piezoelectric material are provided with silver membrane electrode respectively, and the magnetostrictive rods is equipped with a signal output lead. The sensor can detect the alternating current without power supply, so the sensor is an energy-saving device with zero power consumption. The sensor has the advantages of small volume and low weight, can detect the AC magnetic field bandwidth ranging from 500Hz to 70kHz, and keeps a good linear relation between the output voltage and the magnetic field amplitude. The sensor adopts a thin rod structure, thus greatly reducing the volume of the sensor, enhancing the sensitivity and the bandwidth of the sensor. A bias magnetic field provided for the thin rod is greatly reduced for using small size of the magnetostrictive material, and can be integrated with a sensitive body. The sensor can be applicable to passive detection of the alternating magnetic fields.

A method for processing nuclear magnetic resonance (NMR) measurement data includes: receiving, with a processor, NMR measurement data obtained from an NMR tool, the NMR measurement data being affected by a motion artifact and having a first echo train obtained with a long polarization time TWET and a second echo train obtained with a short polarization time TWTL that is shorter than TWET; and at least one of (i) reducing, with a processor, an effect on the NMR measurement data of the motion artifact using the first echo train and the second echo train and (ii) identifying, with a processor, the motion artifact using the first echo train and the second echo train; wherein the motion artifact is related to a magnetic field magnitude that varies in a volume of interest due to a motion of the NMR tool.

A system providing an inductive power and data link between an external transmitter and miniature internal receiver is presented. The system is suited to applications where the receiver must be of a small size and the system must consume very little power, such as an implanted biomedical device. The system is also compatible with systems where bi-directional communications are required. The novel transmitter and receiver form an improved forward data telemetry system. The transmitter consists of a Class-E converter with its optimum operating frequency being synchronously, instantaneously and efficiently altered in accordance with the data to be transmitted, thereby producing an FSK modulated magnetic field of substantially constant amplitude. The constant amplitude output allows for the continuous, data-independent transfer of power to the miniature receiver and its associated electronics. The present invention also represents an improvement over the high efficiency Class-E converters previously patented by the inventors. The receiver consists of a coil and an integrated rectifying system to recover operating power from the incident magnetic field, as well as an FSK demodulator whose operation is based on the multiphase comparison of charging times of integrated capacitors. The described FSK demodulator approach removes deleterious effects resulting from low-frequency changes in the transmitter frequency, and eliminates time distortion artifacts generated by circuit imbalances and asymmetries in the power recovery process. The combination of the transmitter and receiver improvements yields a reliable data transfer system unaffected by circuit imbalances and incidental variations in the amplitude and frequency of the magnetic field.

The invention discloses an electronic device electromagnetic environmental effect test system and test method under an electromagnetic pulse compound field environment. A tested electronic device is fixed to a tested posture control table and placed in a uniform field test area, the tested electronic device is set to a certain working state by using an electronic device working state controller, and the tested posture control table is adjusted, a magnetic field control circuit and an electronic field control circuit are controlled to set a magnetic field amplitude value and an electronic fieldamplitude value, a magnetic field generator and an electronic field generator are subjected to linkage and trigger, and a compound field is formed to perform an irradiation effect test. The magneticfield amplitude value, the electronic field amplitude value and delaying time are continuously changed from low to high, responding phenomenon and responding signals of the tested electronic device under different interference source parameters are recorded, and effect laws are analyzed. The electronic device electromagnetic environmental effect test system and test method under the electromagnetic pulse compound field environment ensure standardization and rationality of the electromagnetic environmental effect test of the electronic device, improve accuracy of the electromagnetic environmental effect test of the electronic device, and are suitable for carrying out relative research work of an electromagnetic pulse compound field environmental effect test of a ground nuclear explosion source area.

The invention discloses a field-circuit coupling analysis method for radial electromagnetic vibration of a motor. The method comprises the steps of a) performing calculation by utilizing a closed slotfinite element model of the motor to obtain an air-gap magnetic field of a permanent magnet; b) according to a characteristic of synchronous rotation of harmonics in the magnetic field of the permanent magnet, performing analysis; c) according to the arrangement of a motor winding, performing harmonic analysis on armature reaction magnetomotive force; d) performing FFT analysis for a magnetic field model obtained by magnetic permeance of each harmonic, and in combination with a time harmonic number and a rotation direction in the magnetomotive force, obtaining a space number, a rotation direction, an initial phase and a magnetic field amplitude value of the magnetic field of each harmonic; e) performing vector synthesis on the magnetic fields of all the harmonics obtained by analysis in the steps a)-d); f) transmitting a radial force wave acting on the surface of a stator to a yoke part through a modulation effect of stator teeth to generate vibration; and g) performing scanning analysis on a stator mode by adopting a frequency sweeping method to obtain a resonant frequency of each low order. According to the method, the locating of a source of the radial electromagnetic vibrationof the motor is more accurate; and the vibration characteristic can be quickly assessed.

A method for determining the location of an underground sonde transmitter is disclosed. In some embodiments, the method includes measuring a set of complex electromagnetic field magnitude and phase strengths at one or more of positions while traversing a target sonde path at any angle using one or more electromagnetic coil sensors, modeling a set of expected complex electromagnetic strengths of a hypothetical sonde at the one or more of positions for one or more of the electromagnetic coil sensors, the set of expected electromagnetic field values corresponding to a model for the target sonde, and estimating parameters related to the target sonde based on the residual error between the measured set of complex electromagnetic field values and the modeled set of expected complex electromagnetic field strengths, wherein a final estimated parameter set is determined after the residual error has converged to a minimum tolerance.

The invention relates to a magnetic resistance imaging sensor array which comprises a medium magnetic field stimulation and offset device, a magnetic resistance sensor chip, a plurality of magnetic resistance inducting elements, an electric excitation source, an element selecting circuit and an output signal circuit, wherein the magnetic resistance sensor chip comprises a main surface and an inducting surface, and an axis X and an axis Y which are perpendicular to each other are built in the main surface; the magnetic resistance inducting elements for forming an array are arranged in the inducting surface, one or more magnetic resistance inducting elements, of which the main inducting axes are parallel to the direction of the axis X, are X-axis inducting elements, and one or more magnetic resistance inducting elements, of which the main inducting axes are parallel to the direction of the axis Y, are Y-axis inducting elements; the electric excitation source is used for the excitation of the magnetic resistance inducting elements; the element selecting circuit is used for selecting the magnetic resistance inducting elements. The magnetic resistance imaging sensor array provided by the invention can be used for measuring magnetic field amplitude and magnetic field gradient in the axial direction, and the double-axis sensing capability enables pictures to be clearer and have fewer blind spots; the element selecting circuit can be used for monitoring absolute value and difference value of the magnetic field at any time and on any required time sequence.

A digital output semiconductor magnetic field sensor integrated circuit provides a low-cost and dense packaging solution for providing digital indicators of magnetic field magnitudes. A delta-sigma modulator based analog-to-digital converter (ADC) is integrated on a die with a semiconductor magnetic field sensor. The delta-sigma modulator provides for noise-shaping the sensor output and the co-location of the sensor and the converter on the die provides for improved noise immunity. The current loops of the ADC and digital interface are made as small as possible and are disposed on the die so that they are orthogonal to the axis of the magnetic field sensor, so that noise from the converter operation is isolated from the sensor.

A method is disclosed for analyzing body composition. The method includes inducing a static magnetic field in the body. The static magnetic field has a known distribution along a longitudinal axis of the body. A radio frequency magnetic field is induced in the body. The radio frequency and a bandwidth thereof are selected to induce nuclear magnetic resonance phenomena in a selected axial segment along the body. Nuclear magnetic resonance phenomena are from the selected axial segment. Composition is determined from the magnetic resonance signals. The measurement may be repeated in different axial segments by changing the static field amplitude or a frequency of the RF magnetic field. In some embodiments, a gradient field is superimposed over the static field.

Sensor devices and methods for calculating an orientation of a sensor device including a magnetometer are disclosed. In one embodiment, a method of computing an orientation of a sensor device includes receiving a current magnetic field reading including at least a magnetic field magnitude, calculating a difference between the current magnetic field magnitude and a reference magnetic field magnitude, and comparing the difference between the current magnetic field magnitude and the reference magnetic field magnitude with a threshold. The method further includes adjusting a trust value of the magnetometer such that the trust value is decreased if the difference between the current magnetic field magnitude is greater than or equal to the threshold, and computing an orientation of the sensor device based at least on the trust value and the current magnetic field reading, wherein the trust value affects a reliance on the magnetic field reading in computing the orientation.

Aged deterioration of ferromagnetic construction materials is nondestructively evaluated by applying to an evaluating material a magnetic field whose magnetic field amplitude is rather low, distinguishing various lattice defects, and quantifying them separately. A method includes obtaining a stress-strain relation in advance by a tensile test, evaluating a minor hysteresis loop (reference minor loop) while applying an applied stress (σ) thereto, obtaining correlation between physical quantities for evaluating aged deterioration, obtaining a subject minor hysteresis loop (subject minor loop) by a tensile test, obtaining measured values of the physical quantities from the loop, and evaluating aged deterioration of the evaluating material from the measured values.

A closed loop broadband geophone which is made by using a high performance method to measure a mechanical vibration is disclosed. All coil portions of the two or more coil sets are located in at least 4 separate recesses of the bobbin. Each coil portion of these coil sets has an individual magnetic field magnitude using Faraday's Law and Lorentz's Law. This mathematic method, significantly improves the accuracy of both measuring the mechanical vibration and providing feedback control to the sensor coils. These coil sets are connected to an electronic device which processes the measuring signal and a feedback signal to the sensing coil as a precision digital forcing signal for a reference position.

The present invention discloses a position detection method based on flexible traveling wave pre-excitation and a non-contact electric energy transmission device. The non-contact electric energy transmission device comprises a power conversion unit for pre-excitation, a pre-excitation winding, a primary side magnetic core, a primary side controller, a secondary side power winding, a secondary sidemagnetic core, a load and a secondary side power conversion unit. The position detection method comprises the steps that: free, flexible and variable excitation is applied to a primary side pre-excitation winding in advance to construct flexible traveling waves with adjustable magnetic field amplitudes, wave peaks and wave trough positions, a variable excitation extreme value is employed to search and find output feedback or excitation features corresponding to the peak of primary side sampling signals to determine and obtain the center position of the secondary side winding so as to provideposition information for alignment of the primary and secondary side winding or non-contact electric energy transmission system control. According to the position detection method based on flexible traveling wave pre-excitation, the primary side pre-excitation winding can be a primary side power emission winding, and can be additional winding. The method is suitable for two typical secondary sidewinding structures (a disc type and a DD type).

The invention relates to the field of superconducting electrical engineering and especially relates to a superconducting tape current transfer capability measuring probe, a measuring device and a method thereof. The superconducting tape current transfer capability measuring probe comprises a magnetic circuit, a detection winding and a measuring circuit which is connected to the detection winding. The magnetic circuit comprises a magnetic circuit core, an excitation winding and an adjustable power supply which provides current to the excitation winding. The excitation winding and the detection winding are respectively wounded around the magnetic circuit core which is provided with a slot for containing a superconducting tape sample to be measured. A closed magnetic circuit is formed by the magnetic circuit core and the slot. The magnetic field amplitude in the slot is adjusted through the excitation winding and the adjustable power supply which provides current to the excitation winding, and the detection winding and the measuring circuit which is connected to the detection winding measure the current transmission capacity of the superconducting tape sample to be measured in the slot. The superconducting tape current transfer capability measuring probe can measure the local current transmission characteristic of a superconducting tape along a tape width direction and can measure the overall current transmission characteristic of the superconducting tape in an external magnetic field.

A method and system for determining a maximum function for a magnetic resonance imaging scanner. The maximum function indicates the upper bound of a magnetic field magnitude in an examination volume in dependence on activation signals of magnetic coils acting on the examination volume. The examination volume is divided into a plurality of partial volumes. The method determines matrices (MB), which, when multiplied by a vector of the activation signals of the magnetic coils, indicate a resultant square of the magnetic field magnitude for each partial volume.

A method for determining the location of underground cables and pipes is disclosed. In some embodiments, the method includes measuring a set of electromagnetic field magnitudes and phases at a plurality of positions while traversing a target line parallelly using 3D electromagnetic coil sensors, the 3D electromagnetic coil sensors being orthogonally oriented to the target line, modeling a set of expected complex electromagnetic field magnitudes of a single underground conductor at each of the positions to form a set of values corresponding to a set of individual models for the target line, determining which of the set of individuals models is a best model, determining confidence information at each of the positions based on a comparison between the measured set of complex electromagnetic magnitudes and phases and the best model, and determining parameters at each of positions related to the target line from the best model.

The invention discloses a standard fluctuating magnetic field reproducing device and a method. The device comprises a moving axis type fluctuating magnetic field coil device and a fluctuating magnetic field exciting device, wherein the moving axis type fluctuating magnetic field coil device comprises a magnetic axis detector, a fluctuating magnetic field coil body and a magnetic axis adjusting table, the fluctuating magnetic field coil body is of a tricyclic three-route winding structure which is axisymmetric, and the fluctuating magnetic field exciting device comprises a random waveform generator, a linear power amplifier, a signal conditioning unit, a current precision measurement unit and a control software. The fluctuating magnetic field exciting device is capable of outputting signals which are stable in amplitude and continuous in frequency change under the situation of load impedance change by means of the current measuring and feedback control technology. Magnetic signals reproduced by the device are composed of constant magnetic field components and alternating magnetic field components, magnetic field amplitudes are stabilized within the range of 20 microteslas and 100 microteslas and do not change along with frequency change, and magnetic field frequencies can change continuously within the range of 0.1 hertz and 1 kilohertz.

The invention discloses a shimming coil optimization design and manufacturing method and a structure thereof, and relates to the technical field of the nuclear magnetic resonance gyroscope. The designflow is as follows: S1, determining to-be-optimized parameters r0, L0, D, m and e; S2, establishing an optimization model, and determining r0, L0, D, m and e; S3, designing a shimming coil satisfyingthe minimum constraint condition volume; the manufacturing method comprises the following steps: S1, determining a substrate; S2, selecting electrifying conductors; S3, mounting the electrifying conductors on the substrate; S4, communicating each line of electrifying conductor; and S5, plugging a male connector and in a female connector. The shimming coil manufactured through the method can control the coil volume when the coil magnetic field amplitude and the uniformity constraint are satisfied; the current direction of the electrifying conductor is vertical to a central axis of the substrate, and the stray magnetic field is reduced; the output conductor and the connecting line are arranged with the same current size and opposite directions, the stray magnetic field produced by the connecting line can be counteracted, and the coil magnetic field precision is guaranteed.

The invention discloses a medium manganese steel martensite phase transformation magnetic measurement device, which comprises a magnetic shielding space and a gantry-type measurement frame. The medium manganese steel martensite phase transformation magnetic measurement device also comprises a probe clamp fixedly arranged in the gantry-type measurement frame, a magnetometer probe arranged under the probe clamp, a fluxgate magnetometer digital displayer connected with the magnetometer probe and arranged outside the magnetic shielding space, a non-magnetic sliding table arranged under the magnetometer probe and used for placing medium manganese steel samples and positioning sample coordinates, a screw rod connected with the non-magnetic sliding table and used for enabling the non-magnetic sliding table to carry out reciprocating rectilinear movement, and a fixation base arranged on the gantry-type measurement frame and used for fixing the two ends of the screw rod. The DC remanent magnetism in the magnetic shielding space is 1mGs. The medium manganese steel martensite phase transformation magnetic measurement device and the realization method thereof belong to nondestructive test, not only can qualitatively judge the content of martensite in medium manganese steel and measure positive correlation relation between the magnetic field amplitude and sample impact toughness, but also is flexible in detection mode and does no harm to human body.

An apparatus, method, and system are disclosed for improving uniformity of RF magnetic field in an MRI system, and thereby improving both signal-to-noise ratio and uniformity of imaging sensitivity across a sampling volume, to provide more uniform MRI images. A passive LC resonator develops induced EMF and induced currents in a primary RF magnetic field; the secondary magnetic field produced thereby can counteract magnetic field amplitude gradients to produce a more homogeneous RF magnetic field. In systems with separate transmit and receive coils, a shunt detuning circuit is pulsed ON to prevent interference during the transmit period. In a dual-frequency MRI machine (e.g. 19F and 1H), the RF magnetic field at the lower operating frequency can be homogenized by tuning the resonance of the passive resonator between the two operating frequencies. Another resonator can improve RF field uniformity at the higher operating frequency. Variants and experimental results are disclosed.

The invention relates to a method and a device for imaging magnetic resonance electromagnetic characteristic parameters of human body biological tissues. The method comprises the following steps of respectively carrying out spin echo and proton density imaging sequence scanning to obtain image data, dividing the spin echo reconstruction image data by the proton density image data to obtain decoupled pure receiving magnetic field data, and on the basis of pure receiving magnetic field data, conducting synchronous reconstruction by utilizing a convection-reaction-diffusion or gradient indirect inversion algorithm to obtain parameter value distribution of the electrical conductivity, the dielectric constant and the magnetic conductivity of the tissue. A result obtained by utilizing the spin echo sequence and receiving magnetic field amplitude and phase component inversion does not contain contribution of quasi-static frequency components related to main magnetic field uniformity distortion in image data acquisition. The measurement process is noninvasive, and the obtained measured value does not need to be assisted by a contrast agent.