scholarly journals A broadband two axis flux-gate magnetometer

1998 ◽  
Vol 41 (3) ◽  
Author(s):  
P. Palangio
Keyword(s):  
Magnetic Field ◽  
Low Frequency ◽  
High Sensitivity ◽  
Magnetic Sensors ◽  
Frequency Range ◽  
Field Station ◽  
Low Weight ◽  
Highly Sensitive ◽  
Flux Gate ◽  
Magnetic Field Variations

A broadband two axis flux-gate magnetometer was developed to obtain high sensitivity in magnetotelluric measurements. In magnetotelluric sounding, natural low frequency electromagnetic fields are used to estimate the conductivity of the Earth's interior. Because variations in the natural magnetic field have small amplitude(10-100 pT) in the frequency range 1 Hz to 100 Hz, highly sensitive magnetic sensors are required. In magnetotelluric measurements two long and heavy solenoids, which must be installed, in the field station, perpendicular to each other (north-south and east-west) and levelled in the horizontal plane are used. The coil is a critical component in magnetotelluric measurements because very slight motions create noise voltages, particularly troublesome in wooded areas; generally the installation takes place in a shallow trench. Moreover the coil records the derivative of the variations rather than the magnetic field variations, consequently the transfer function (amplitude and phase) of this sensor is not constant throughout the frequency range 0.001-100 Hz. The instrument, developed at L'Aquila Geomagnetic Observatory, has a flat response in both amplitude and phase in the frequency band DC-100 Hz, in addition it has low weight, low power, small volume and it is easier to install in the field than induction magnetometers. The sensivity of this magnetometer is 10 pT rms.

Topographic Correction for the Data of SQUID-based TEM Using a Ground Loop

2019 ◽  
Vol 24 (1) ◽  
pp. 111-117
Author(s):  
Yanju Ji ◽  
Yi Zhao ◽  
Shangyu Du ◽  
Dongsheng Li ◽  
Yi Zhang ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Quantum Interference ◽  
Low Frequency ◽  
High Sensitivity ◽  
Absolute Error ◽  
Correction Method ◽  
Topographic Effects ◽  
Topographic Correction ◽  
Transient Electromagnetic ◽  
Ground Loop

Superconducting quantum interference device (SQUID) can be used to detect the signal of transient electromagnetic method (TEM) due to its superiority of high sensitivity in the low frequency range. However, the measuring direction of SQUID is hardly consistent with the normal direction of the transmitting coil of a TEM system because of the undulating topography in the field. In this case, the central magnetic field measured by SQUID is only a component of the theoretical central magnetic field. There will be larger errors if we directly use the measured central magnetic field for geological interpretation. To solve this problem, we propose a topographic correction method for the data of SQUID-based TEM using ground loop. The theoretical central magnetic field of the ground loop is calculated after the trapezoidal transmitting current wave is turned off. Then, we use the theoretical central magnetic field of the ground loop as the reference to correct the measured central magnetic field of SQUID-based on the trigonometric function relation between the measuring direction of SQUID and the topographic inclination. The experiment of SQUID-based TEM using a ground loop was carried out in the field. The result shows that at the measurement point with larger topographic inclination, the average absolute error of the measured central magnetic field reduces significantly with the proposed correction method. This method can also be applied to the correction of complex topographic effects when using SQUID to measure three components of magnetic field.

scholarly journals An overview of commercially available Teslameters for applications in modern science and industry

ACTA IMEKO ◽  
2017 ◽  
Vol 6 (1) ◽  
pp. 43 ◽  
Author(s):  
Dragana Popovic Renella ◽  
Sasa Spasic ◽  
Sasa Dimitrijevic ◽  
Marjan Blagojevic ◽  
Radivoje S Popovic
Keyword(s):  
Magnetic Field ◽  
Temperature Coefficient ◽  
Low Frequency ◽  
Modern Science ◽  
Calibration Procedure ◽  
Magnetic Sensors ◽  
Performance Ratio ◽  
Frequency Noise ◽  
Hall Probe ◽  
Sensitive Volume

<p>The Hall-effect based Teslameters (also called Gaussmeters) are the mostly applied instruments for measuring DC and AC magnetic flux densities in modern science and industry. This paper gives an overview of commercially available Teslameters at the high-end performance level. The Teslameters have been evaluated by following characteristics that are published by suppliers: probe dimensions, magnetic field sensitive volume, accuracy, magnetic resolution, measurement range, frequency bandwidth, temperature coefficient sensitivity, and price/performance ratio.</p><p>The Teslameter that best matches the measurement needs in various application fields incorporates a 3-axis integrated Hall probe, analog electronics based on the spinning-current technique, an analog-to-digital converter, an embedded computer, and a touch-screen display. The 3-axis Hall probe is a single silicon chip integrating both horizontal and vertical Hall magnetic sensors and a temperature sensor. The spinning-current eliminates most of the Hall probe offset, low-frequency noise, and the planar Hall voltage. The errors due to the Hall sensor non-linearity and the variations in the probe and electronics temperatures are eliminated by a calibration procedure. The errors due to the angular imperfections of the Hall probe are eliminated by a calibration of the sensitivity tensor of the probe. This Teslameter can measure magnetic field vectors from about 100 nT to 30 T, with the spatial resolution of 100 µm, magnetic resolution ±2 ppm of the range, the accuracy 0.002 % of the range, a temperature coefficient less than 5 ppm/°C, and angular errors less than 0.1°.</p>

High-Sensitivity Tunnel Magnetoresistance Sensors Based on Double Indirect and Direct Exchange Coupling Effect*

2021 ◽  
Vol 38 (12) ◽  
pp. 128501
Author(s):  
Xiufeng Han ◽  
Yu Zhang ◽  
Yizhan Wang ◽  
Li Huang ◽  
Qinli Ma ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Noise Level ◽  
Exchange Coupling ◽  
Coupling Effect ◽  
High Sensitivity ◽  
Wheatstone Bridge ◽  
Low Noise ◽  
Magnetic Sensors ◽  
Tunnel Magnetoresistance ◽  
Current Detection

Abstract Detection of ultralow magnetic field requires magnetic sensors with high sensitivity and low noise level, especially for low operating frequency applications. We investigated the transport properties of tunnel magnetoresistance (TMR) sensors based on the double indirect exchange coupling effect. The TMR ratio of about 150% was obtained in the magnetic tunnel junctions and linear response to an in-plane magnetic field was successfully achieved. A high sensitivity of 1.85%/Oe was achieved due to a designed soft pinned sensing layer of CoFeB/NiFe/Ru/IrMn. Furthermore, the voltage output sensitivity and the noise level of 10.7 mV/V/Oe, 10 nT/Hz1/2 at 1 Hz and 3.3 nT/Hz1/2 at 10 Hz were achieved in Full Wheatstone Bridge configuration. This kind of magnetic sensors can be used in the field of smart grid for current detection and sensing.

Magnetic Sensors for Space Applications

2018 ◽  
pp. 248-283 ◽  
Author(s):  
Neoclis Hadjigergiou ◽  
Marios Sophocleous ◽  
Evangelos Hristoforou ◽  
Paul Peter Sotiriadis
Keyword(s):  
Magnetic Field ◽  
Quantum Interference ◽  
Measurement Techniques ◽  
General Information ◽  
Magnetic Sensors ◽  
Normal Operation ◽  
Space Applications ◽  
Flux Gate ◽  
Magneto Resistance ◽  
The Magnetic Field

This chapter is composed of three parts. The first is an introductory part, providing general information about magnetism and related phenomena. Magnetic materials are also discussed and presented. Afterwards, the magnetic field and various measurement techniques are discussed. In the second part, different magnetic sensors used in a laboratory or space are presented. Magnetic sensors that are discussed include anisotropic magneto-resistance (AMR), giant magneto-resistance (GMR), giant magneto-impedance (GMI), flux-gate and superconducting quantum interference device (SQUID). Although some of them may be outdated and well known, they are widespread and they still pose an excellent choice for certain applications. Magnetic cleanliness is an important factor both in calibration and in normal operation of a system; in the third part, current techniques to isolate a system from the external magnetic field providing cleanliness are discussed.

Effect of Magnetic Field on the Magnetic Structure of Nanocrystalline Electroplated NiFe Layers

2005 ◽  
Vol 23 ◽  
pp. 167-170
Author(s):  
Xiao Ping Li ◽  
Z.J. Zhao ◽  
T.B. Oh ◽  
H.L. Seet
Keyword(s):  
Magnetic Field ◽  
Magnetic Structure ◽  
High Frequency ◽  
Longitudinal Magnetic Field ◽  
High Sensitivity ◽  
Frequency Range ◽  
Gmi Effect ◽  
Double Peaks ◽  
Field Sensor ◽  
The Magnetic Field

In order to develop high sensitivity micro sensors for bio-magnetic field using NiFe electroplated composite sensing elements, it is important to study how different plating processes can affect the magnetic properties in terms of the chemical composition and magnetic structure of the plated layer. In this study, to study the effect of the magnetic field on the magnetic structure of the electroplated NiFe layers, magnetic controlled plating in which a longitudinal magnetic field ranging from 0 to 400 Oe is applied during nanocrystalline electroplating of permalloy Ni80Fe20 layer of 2 µm thick onto a 20 µm diameter Cu wire. The magnetic structure of the plated layers is studied by investigating the Giant magneto-impedance (GMI) effect of the plated layer. GMI has been measured from a frequency range of 100 kHz to 50 MHz. It is observed that under conventional electroplating without an external magnetic controlling field, the anisotropy of the plated layer is generally circumferential as indicted by the double peaks of the MI curves in testing at high frequency. When a longitudinal magnetic field is applied during electroplating, the plated layer shows single peak MI curves, suggesting that the anisotropy is changed from circumferential to longitudinal. The results also show that the sensitivity and resolution of a magnetic field sensor is improved greatly by changing the anisotropy of the plated layer from circumferential to longitudinal.

Low-Frequency Magnetic Localization of Capsule Endoscopes with an Integrated Coil

2021 ◽  
Vol 6 (1) ◽  
pp. 38
Author(s):  
Samuel Zeising ◽  
Rebecca Seidl ◽  
Angelika Thalmayer ◽  
Georg Fischer ◽  
Jens Kirchner
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Flux Density ◽  
Eddy Currents ◽  
Low Frequency ◽  
Magnetic Sensors ◽  
Video Frame ◽  
Magnetic Flux Density ◽  
Field Source ◽  
Localization Method

Wireless capsule endoscopy is a promising and less invasive alternative to conventional endoscopy. A patient swallows a small capsule with an integrated camera to capture a video of the gastrointestinal tract. For accurate diagnosis and therapy, the capsule position in terms of the travelled distance must be known for each video frame. However, to date, there is no reliable localization method for endoscopy capsules. In this paper, a novel magnetic localization method is proposed. A coil as a magnetic field source is integrated into a capsule and fed with a low-frequency alternating current to prevent static geomagnetic field interference. This alternating magnetic field is measured by twelve magnetic sensors arranged in rings around the abdomen. The coil and the capsule batteries were designed based on the geometry and power supply of a commercially available endoscopy capsule and simulated by COMSOL Multiphysics software. In this way, the coil position and orientation were determined with an accuracy below 1 mm and 1°, respectively. As an analytic model for the magnetic flux density of the coil in that setup, a modified dipole model was derived. It was used to show that the batteries help to increase the amplitude of the magnetic flux density. The model is valid when signals below 100 Hz are applied, and no eddy currents are generated within the batteries. It is concluded that the magnetic flux density generated by the developed coil would be measurable with state-of-the-art magnetic sensors.

Study of Energy Methods to Strongly Nonlinear Vibrations in a Loudspeaker Cone-Shaped Shell

2005 ◽  
Author(s):  
F. D. Zong ◽  
Z. L. Zhang ◽  
J. W. Fang ◽  
Y. J. Yu ◽  
Q. Chen
Keyword(s):  
Magnetic Field ◽  
Limit Cycles ◽  
Nonlinear Oscillations ◽  
Low Frequency ◽  
Approximate Solutions ◽  
Energy Methods ◽  
Frequency Range ◽  
Strongly Nonlinear ◽  
Harmonic Vibrations ◽  
Strongly Nonlinear Oscillations

H. F. Olson points out that a loudspeaker cone-shaped shell, as a nonlinear oscillation system, can be described as the Classical Duffing Equation in low frequency range. Yoshinisa, a Japanese scholar, studied the nonlinear phenomena of the loudspeaker cone-shaped shell in low frequency range driven by a stable galvanic source, including the resonance frequency changing with amplitude and leap phenomena. But their research were not taken the influence of nonlinear magnetic field into account. Its work mostly related to getting solution of nonlinear differential equation by the Numerical Calculation, but it didn’t get approximate solutions. Through research and analysis of the experiment on the loudspeaker cone-shaped shell, we obtain the Generalized Duffing Equation that’s a strongly nonlinearity system which is used to describe the loudspeaker cone-shaped shell driven by a stable voltage source, it considers the nonlinearity of mechanical resilience and the magnetic field. This paper focuses on first finding the approximate solutions (limit cycles) of strongly nonlinear oscillations and nonlinear heteronomy of the loudspeaker cone-shaped shell in low frequency range by use of energy methods. They obtained the equation relating to the forced vibration amplitude with frequency and the corresponding relation about phase versus frequency, and analysed particularly complete stability of limit cycles belonged to the strongly nonlinear systems, and drew several important conclusions. (1) As to strongly nonlinear oscillations of the loudspeaker cone-shaped shell in low frequency range, it is only likely to appear main oscillation and odd-order sub-harmonic oscillations. But it cannot appear super-harmonic vibrations and even-order sub-harmonic vibrations. (2) As to strongly nonlinear oscillations of the loudspeaker cone-shaped shell in low frequency range, two cases about main oscillation and one third sub-harmonic oscillation whose approximate solutions accord with numerical solutions very well. (3) It is worthy to study strongly nonlinear oscillations of commonly thin shell structure such as a loudspeaker cone-shaped shell by use of energy methods, and we will continue to carry out this research.

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