Measurement Of Magnetic Field Intensity Research Articles

Design of a magnetic field and temperature fiber sensor based on Fabry–Pérot interferometer and OAM interrogation

We have designed a Fabry–Pérot interferometric fiber sensor based on the principal component analysis (PCA) assisted orbital angular momentum (OAM) interrogation for simultaneous measurement of magnetic field intensity and temperature. A hollow core fiber sandwiched between two segments of single mode fiber serving as the sensing probe, is introduced to the Gaussian interference arm. Encapsulated with magnetic fluid, the intensity and phase of Gaussian beam are highly sensitive to the variations of magnetic field and temperature, exerting a modulation on the intensity and rotation angle of OAM interferograms. A dual-parameter sensing matrix to discrimination the cross-sensitivity could be established via the PCA-assisted OAM interrogation. The minimum sensing resolutions of magnetic field and temperature are calculated as 0.06 G and 0.0079 °C, respectively.

A permanent magnet tool in ultrasonic assisted magnetic abrasive finishing for 30CrMnSi grooves part

The grooves of hydraulic cylinders are the main feature of its sealing structure. However, improving of the surface quality of grooves is a challenge problem using the present processing method such as magnetic abrasive finishing (MAF) and ultrasonic assisted magnetic abrasive finishing (UAMAF). A novel permanent magnet tool in UAMAF is developed for finishing 30CrMnSi grooves parts. The trapezoidal cross-section permanent magnet with a curved bottom is designed and applied with ultrasonic vibration. The ultrasonic vibration is produced by a 50 kHz piezoelectric transducer and transferred to a horn. The horn and permanent magnet are connected by the metal welding glue. The permanent magnet can absorb and excite bonded magnetic abrasives to process the surface of the grooves. Experimental measurements of magnetic field intensity and ultrasonic amplitude of the permanent magnet tool are conducted to certify the characteristics of UAMAF. The magnetic field intensity in the middle position is higher than the other positions on the curved bottom of the permanent magnet. The average ultrasonic amplitude of the permanent magnet at the curved bottom is 5.076 μm, and the maximum ultrasonic amplitude is 8.26 μm. Ultrasonic vibration slightly weaken the magnetic field intensity by 0.2 mT. The surface quality of the bottom surface and the sidewall of grooves parts under UAMAF and MAF are measured experimentally. Advantages of UAMAF are noticeable in the middle and later stages of processing between 15 and 25min. The boron carbide abrasives can allow for the lowest surface roughness value of 0.507 μm and the greatest roughness decline rates of 90.79% under UAMAF. The material removal ratio of UAMAF is 1.9 times than that of MAF. UAMAF can achieve a more uniform surface quality compared to MAF. The sidewall of grooves parts under UAMAF has a better surface quality than the bottom of grooves parts. It provides a novel method for finishing the grooves of hydraulic cylinders.

A New Structural Health Monitoring Approach Based on Smartphone Measurements of Magnetic Field Intensity

In this paper, a new structural damage detection approach is proposed, based on monitoring of the magnetic field intensity variations using smartphones. Experimental and numerical studies are conducted on steel plates to verify the efficiency of the proposed approach. Various damage scenarios are introduced to the steel plates. Then, a smartphone magnetometer sensor is deployed to measure the changes of the magnetic flux due to damage progression. The experimental and numerical results agree well with each other. Based on the results, the magnetic field intensity increases as the damage progresses. Furthermore, the damage detection accuracy declines as the distance of the smartphone increases from the steel plate surface. The proposed method can be considered as a promising, cost-effective and crowdsourcing sensing platform empowered by citizens for structural health monitoring of civil infrastructure systems.

Design, Fabrication, and Characterization of a Water-Cooled Electromagnet and Magnetic Field Mapping

In this paper, a prototype solenoid magnet was designed and fabricated to be used in Micro Wave Discharge Ion Sources in the Turkish Accelerator Center Proton Accelerator Project and magnetic field mapping was performed with an experiment and also investigation was conducted by using finite element method. For this, a water-cooled electromagnet was designed and fabricated from 1010 steel with a thickness of 10 cm. Magnetic field sensor was connected to a new designed robotic arm and 2570 magnetic field intensity measurements were performed in the core of magnet with the size of 20 cm diameter and 10 cm depth of cylinder. The robotic arm was driven by three stepper motors and the measurement was automated with the Arduino physical programming platform. The UGN3503U Hall Effect sensor was used to measure the magnetic field and for the data processing ROOT was used. The magnetic field distribution inside the core of the solenoid magnet was investigated by using the finite element method. The commercial version of The Flexible Generalized Minimal Residual method (FGMRES) solver (built-in COMSOL) was used for the numerical part and magnetic field was calculated and compared with experiment to correlate simulation accuracy of this study. Abstract

Fiber-Optic Vector Magnetic Field Sensor Based on Mode Interference and Magnetic Fluid in a Two-Channel Tapered Structure

An innovative approach to high-sensitivity simultaneous intensity and direction measurement in a two-channel tapered sensor is proposed and demonstrated. The sensor is comprised of magnetic fluid (MF)- filled micro-capillary and two accompanying micro-fiber, thus enabling evanescent interaction to take place between the optical mode in the capillary and MF. Given the magnetic nanoparticles (MNPs) of MF manifest anisotropic magnetic field. Experimental and numerical simulations were performed simultaneously, which provided a better understanding of the interaction between light and MF in addition to clarifying the dynamic process of MNPs within MF with the assistance of varying magnetic field. The experimental results are well consistent with the numerical simulation results and show that the sensitivity of this sensor reaches up to 244 pm/mT, with the direction error being merely ±1.4°. Therefore, the proposed sensor exhibits a unique sensitivity for the measurement of magnetic field intensity and direction in 3D space, which makes it best suitable for applications in transportation, medicine, and smart device.

Measurement of Magnetic Field Intensity within Captain Elechi Amadi Polytechnic Rumuola, Rivers State, Nigeria


 
 
 
 The measurement of magnetic field intensity within Captain Elechi Amadi Polytechnic, Rumuola was carried out with the aid of a handheld Bentech (GM-3120) Model Electromagnetic Radiation Metre. A total of 6 sampled locations were recorded; randomly with six distinct measurement and their coordinates at each of the sampled location with the aid of the global system position satellite (GPS) device. The measurement took place between 2017 November to 2018 March. A minimum value of 0.3417 0.65 T was recorded at the Administrative Block and a maximum value of 1.9767 1.43 T at the Business Centre. The overall mean values of all the sampled locations all fall below the recommended limit for the outdoor magnetic field intensity exposure of 100T of the International Commission of Non-Ionizing Radiation Protection (ICNIRP). The outcome of the measurement reveals that the exposure to magnetic field intensity to staffs, students and commercial workers within the campus of the Captain Elechi Amadi Polytechnic poses no health hazard.
 
 
 
 

A Novel Indoor Positioning Technique Using Magnetic Fingerprint Difference

Utilizing the pattern of magnetic field intensity (MFI) variation over a distance as a fingerprint for indoor positioning of mobile devices has gained increasingly wide attention. However, pattern matching with a large fingerprint is computationally expensive, and magnetometers are vulnerable to ferromagnetic perturbations and prone to have unknown magnetic offset (MO) in MFI measurements, which may result in large positioning error. In addition, the time-varying attitude of mobile devices and unreliable attitude determination with power consuming gyroscopes in mobile devices can render the 3-D MFI measurement useless for indoor positioning. In this paper, we propose a low power consuming and computationally efficient indoor positioning technique using the difference in 2-D (horizontal and vertical) MFI measurements that are collected over a distance, where 3-D accelerometers are used to find the vertical direction, and the MFI measurement difference is used to enhance robustness to unknown MO fixed in the body frame but time varying due to user dynamics in the navigation frame. The analysis of real data verifies that the proposed technique affords superior positioning performance relative to the conventional magnetic fingerprint techniques and achieves a similar performance to the conventional magnetic fingerprint techniques with MO-free measurements.

All-fiber-optic vector magnetometer based on nano-magnetic fluids filled double-clad photonic crystal fiber

We demonstrate a compact all-fiber-optic vector magnetometer based on Mach-Zehnder interferometer by utilizing nano-magnetic fluid filled double-clad photonic crystal fiber (DC-PCF). The magnetic fluid (MF) serving as sensing elements is injected into the micro-channel-arrays of DC-PCF. The magnetometer is constructed by splicing a section of MF-filled DC-PCF between two standard single mode fibers forming a high stable all-fiber structure without any additional sealed capillary. The vector magnetometer has the capability of simultaneous measurement of magnetic field intensity and orientation by monitoring a specific dip wavelength shift or transmission loss of Mach-Zehnder interference spectrum. The magnetometer with response sensitivities of 114.5pm/mT, 1.79dB/mT (X-axis) and 41.9pm/mT, 0.52dB/mT (Y-axis) at two particular orthogonal magnetic field orientations was fabricated and investigated.

DEVELOPMENT OF EMBEDDED SYSTEM FOR REMOTE MEASURING OF DYNAMIC MAGNETIC FIELDS USING ZIGBEE

This paper aims to describe the development and implementation of an embedded system applied to remote measurement of dynamic artificial magnetic fields using Zigbee, which is a set of specifications for wireless data communication (based on IEEE standard 802.15.4). In the implementation of this system, Arduino microcontrolled platforms were used integrated to a Hall effect sensor intended for measuring the strength of these dynamic magnetic fields. The Zigbee technology aims to enable the execution of real-time and in remote character of these measurements of magnetic field intensity, presenting them in a graphical view.

Main field and secular variation candidate models for the 12th IGRF generation after 10 months of Swarm measurements

We describe the main field and secular variation candidate models for the 12th generation of the International Geomagnetic Reference Field model. These two models are derived from the same parent model, in which the main field is extrapolated to epoch 2015.0 using its associated secular variation. The parent model is exclusively based on measurements acquired by the European Space Agency Swarm mission between its launch on 11/22/2013 and 09/18/2014. It is computed up to spherical harmonic degree and order 25 for the main field, 13 for the secular variation, and 2 for the external field. A selection on local time rather than on true illumination of the spacecraft was chosen in order to keep more measurements. Data selection based on geomagnetic indices was used to minimize the external field contributions. Measurements were screened and outliers were carefully removed. The model uses magnetic field intensity measurements at all latitudes and magnetic field vector measurements equatorward of 50° absolute quasi-dipole magnetic latitude. A second model using only the vertical component of the measured magnetic field and the total intensity was computed. This companion model offers a slightly better fit to the measurements. These two models are compared and discussed.We discuss in particular the quality of the model which does not use the full vector measurements and underline that this approach may be used when only partial directional information is known. The candidate models and their associated companion models are retrospectively compared to the adopted IGRF which allows us to criticize our own choices.

보현산천문대 고분산 편광 분광기 개념 설계

We plan to install the polarimetric optics in the AGU(acqusition and guiding unit) of the 1.8 m telescope at the BOAO(Bohyunsan Optical Astronomy Observatory). With this, the spectropolarimetric observations with the resolution of 45,000 and 60,000 in 4,000 to <TEX>$8,000{\AA}$</TEX> ange could be done by the BOES(BOao Echelle Spectrograph). If we use the precision radial velocity measurement capability of the BOES, the accuracy of the magnetic field intensity measurements with this new BOES stokesmeter will be much increased. We present here the design concept of the BOES stokesmeter. Some details on the optics, mechanical parts, fiber parts and the lab test procedures of this stokesmeter are explained.

A temperature-compensated system for magnetic field measurements based on artificial neural networks

This paper presents a personal-computer-controlled system, assembled mainly with IEEE 488 general purpose instruments and aimed at the measurement of magnetic field intensity. The main sensor element in the system is a magnetoresistive field sensor which includes four permalloy strips connected in a Wheatstone bridge configuration. The temperature dependence of this sensor can vary almost 25% in the experimental operating temperature range (20/spl deg/C-100/spl deg/C). In order to overcome this problem, a two-terminal integrated circuit temperature transducer is connected to the system, and its temperature information is used to correct the temperature drift error of the magnetic sensor. Artificial neural networks are used for data reduction and final results show an improvement in the system's accuracy from 20% to 2%.

Measurement of magnetic field intensity by means of NMR. I. Accuracy of measurement

The influence of various parameters (e.g. polarization and intensity of high frequency field, NMR relaxation times, signal to noise ratio of the measuring apparatus) on the determination of NMR resonance point of a nuclear system with exactly known value of gyromagnetic factor is discussed. Special attention is given to the case of real field, which is not stable in time. It is shown that the transverse NMR relaxation time of the nuclei in the sample has to be selected in correlation with the properties of the field (e.g. time instability, spatial inhomogeneity) and of the measuring equipment (e.g. signal to noise ratio), if the lowest obtainable uncertainty of field intensity NMR measurement is to be achieved.

Increasing the accuracy of measurement of magnetic field intensity in permeameters

If the extrapolative transducer is well designed, the amplitude error can be reduced to 2–3% and the angular error to 30–40′. The extrapolative transducer can be constructed without difficulty; it may be used both in the laboratory and in industry.

Experimental evidence of degradation effects in short samples of hard superconductors : Fakan, John C., Lewis Research Center, and Edward R. Schrader, Radio Corp. of America, NASA Technical Note, NASA TN D-2345, June 1964, 11 pp.

It is practicable to obtain accurate measurements of magnetic field intensity in non-uniform fields by the nuclear resonance method with the aid of a set of current-carrying coils which neutralize the field gradient. For use on an electromagnet, a method of controlling the compensating currents by reference to the magnet current is described. This method simplifies the adjustment of the compensating currents. Field gradients up to 150 gauss/cm may be neutralized by the equipment described, which has been used so far in fields ranging from 2 to 10 kilogauss. In the instruments constructed, it has only been necessary to compensate for variations of the field along the two axes normal to the field itself. However, it should be possible to compensate for variation along the axis parallel to the field as well, without difficulty, and the coil arrangement required for this is described also.

The study of the decomposition of a potassium solution in liquid ammonia by the paramagnetic electron resonance method

The quantitative results of measurements of the decomposition of a potassium solution in liquid ammonia at room temperature by paramagnetic electron resonance are given in this paper. Changes of the paramagnetic susceptibility of the solution were measured during the decomposition. Then the results of measurements were converted using data given by other authors and a dependence of the potassium concentration in the solution on the time was thus obtained. The obtained results cannot be explained by previous concepts on the course of this decomposition. A reaction kinetic diagram of this chemical decomposition has already been proposed according to our results. The obtained results show that sufficiently stable solutions can be prepared even at room temperature so that they can be used for longer-lasting physical measurements, e.g. for an accurate measurement of magnetic field intensity.

Dynamics and structure of the outer radiation belt

From an analysis of electron measurements in the Explorer VI satellite (August 7–October 6, 1959) four time-dependent parameters which characterize the outer electron belt have been investigated. They are: (1) the equatorial electron intensity I0; (2) the equatorial range from the earth R0 of the peak intensity; (3) the electron-density distribution along a line of force through the intensity peak; and (4) a measure of the change in electron spectrum with time. These parameters, along with measurements of magnetic field intensity, make it possible to study the origin of the changes in electron intensity and distribution which are known to occur in the outer belt. Several magnetic storms occurred during the observation on Explorer VI. Within the sequence of changes in the outer belt induced by these geomagnetic storms, there are some changes of the parameters which are accounted for only by invoking an irreversible energy gain or loss within the outer belt. The energy gain process appears to be through irreversible local acceleration of electrons. The energy loss process leads to a stable mirror-point distribution characteristic of the periods between geomagnetic storms. The time intervals within which each of these processes is operative are identified. Reversible processes are possibly the cause for other changes. The foregoing analysis rests upon the proof given in this paper that the outer-belt peak intensity coincides over a wide range of geomagnetic latitudes with magnetic field lines of force in the centered dipole approximation. Consequently, the measured electron-intensity maximum is used as a ‘tracer’ of the geomagnetic field lines of force for analyzing changes in the outer belt with time. It is shown that even during geomagnetic storms the trace of the electron-intensity maximum followed a centered dipole line of force. This indicates that at all times the particle-energy density of the radiation belt is much less than the energy density of the magnetic field in the region. The electron fluxes, high-energy proton fluxes, and possible electron spectra are investigated. Two distinct peaks of electron intensity are identified to persist in the outer belt for about 2 months, and it is shown that these peak distributions undergo radial motion during geomagnetic disturbances.

Magnetic Field Measurement Using Ultrasonics

The detection and measurement of magnetic field intensity for purposes of field plotting and uniformity studies is a most important consideration in the field of magnetics. Field plotting and uniformity studies have been conducted on certain sizes of magnetic geometries with rotating coil instruments and Hall generators and quartz crystal magnetometer. The obvious limit of such devices is their minimum resolving power which can be defined in terms of sampling area and mimimum air gap. For the rotating coil instruments, the minimum air gap is 14 in. and the sampling area is roughly 1.2 × 10−2 sq in. Commercially available Hall generators which can be fitted into air gaps of approximately 0.011 in. have sampling areas in the order of 3.2 × 10−3 sq in. Hall generators with sampling areas in the order of 10−7 sq in. have been reported in the literature. Minimum thickness of this type device is presumably less than 0.01 in. The more recent work with the vibrating quartz crystal magnetometer has been used to measure flux density normal to the surface of permanent magnets. The sampling area of this type of equipment is 0.56 × 10−6 sq in. The minimum thickness of this equipment has not yet been reported in the literature. The flux-measuring equipment being described in this paper has a sampling area of approximately 6.25 × 10−6 sq in. and a senstivity of approximately 0.01 × 10−3 v/gauss. The probe consists of a single turn inductor of length 116 in. which vibrates ±0.00005 in. The inductor is fastened to a probe of 0.01 in. thickness and the 0.0001 in. motion is perpendicular to this 0.01 in. probe thickness. The physical geometry and size of this probe permits measurements in a variety of positions relative to the magnetic circuit. This type of probe is applicable for measuring flux density in air gaps as small as 0.017 in. The driving device for this equipment is a 60 Kcps magnetostrictive transducer. The complete probe consists of the transducer reactor, a coupling bar of nonmagnetic stainless steel and the thin strip of the nonmagnetic stainless to which the inductoris fastened. The geometry and size of this thin strip can be changed to accommodate variations in both inductor length and displacement.

A modification of the nuclear resonance method for measurements of non-uniform magnetic fields

It is practicable to obtain accurate measurements of magnetic field intensity in non-uniform fields by the nuclear resonance method with the aid of a set of current-carrying coils which neutralize the field gradient. For use on an electromagnet, a method of controlling the compensating currents by reference to the magnet current is described. This method simplifies the adjustment of the compensating currents. Field gradients up to 150 gauss/cm may be neutralized by the equipment described, which has been used so far in fields ranging from 2 to 10 kilogauss. In the instruments constructed, it has only been necessary to compensate for variations of the field along the two axes normal to the field itself. However, it should be possible to compensate for variation along the axis parallel to the field as well, without difficulty, and the coil arrangement required for this is described also.