Digital Magnetometer Research Articles

Structural, Thermal, and Magnetic Characterization Analysis of Synthesized Fe<sub>3</sub>O<sub>4</sub>-Spinel Ferrite Nanoparticles

Spinel ferrite nanoparticles are potential candidates for multiple biomedical applications. Spinel ferrite nanoparticles have been studied extensively for understanding physical, chemical, electro-optical as well as magnetic properties which are fascinating due to cationic distributions corresponding to tetrahedral sites and octahedral sites in a cubic phase. Biocompatibility and large magnetic moment are basic requirements in spinel ferrite nanoparticles for efficient functioning in specific application purpose. Fe3O4(magnetite) is an important member of spinel ferrite group with high chemical stability and ferrimagetic material property at nanodimension. Superparamagnetic state and biocompatibility of magnetite (Fe3O4) spinel ferrite nanoparticle has already been proven. Spinel ferrite magnetite nanoparticles have been developed based on precipitation of iron oxide using ferric and ferrous ions at the ratio 2:1 in alkaline media at and above 100°C. The experimental parameters have been set to synthesize pure and uniformly sized magnetite nanoparticles. No other phases of iron oxides were detected other than magnetite spinel phase in the XRD result. The average crystal size has been determined from XRD peak broadening. Absorption spectra were investigated using UV-Vis Spectrometer and FTIR. Thermal and magnetic measurements were carried out Digital Scanning Calorimeter and SQUID Magnetometer. One sample of the prepared nanoparticles with polymer coating of polyvinyl alcohol has been studied for superparamagnetic nature. Superparamagnetic particles show saturation value of magnetization 51.26 emu/g at 100 K. ZFC-FC curves for two samples with polymer coating of polyvinyl alcohol and hydroxy-propyl methyl cellulose have also been studied. Keywords: Spinel Ferrite, Magnetite, Ferrimagnetism, Transition metal oxide, Superparamagnetism. Statements and declarations Competing Interests: The authors declare that there is no competing financial interest that are related directly or indirectly to the reported work in this paper. Conflict of interest: There is no conflict of interest. Acknowledgements The Authors are grateful to IISER Bhopal, CRF facility for providing instrumentation facility to characterize magnetic properties. We acknowledge thanks to Lovely Professional University for providing us necessary characterization technique for the XRD analysis and thermal analysis.

Stability Criteria of a High Sensitivity Digital GMI Magnetometer

This article presents a model that allows deriving the stability conditions of a newly developed digital high sensitivity giant magneto-impedance (GMI) magnetometer as a function of the time delay, induced by digital processing, and of the sensitivity. The description of the developed digital magnetometer is given. The transfer function of each involved stage as well as the whole transfer function of the direct open-loop chain were derived. The analysis of the stability was performed by calculating the gain and the phase margins of this transfer function in the Black–Nickols diagram. The experimental results were in good agreement with the modeling and showed that, with a tradeoff between the time delay and the sensitivity, the stability of the magnetometer can be guaranteed.

Patterns of geomagnetic Pc1 pulsations in different solar cycles in the near-equatorial region from the Indian subcontinent

Pc1 geomagnetic pulsations have been investigated at very low latitudes using 13 years of archived records covering solar cycle 20–21 from the equatorial site Choutuppal (CPL, L = 1.03), and 5 years of digital induction coil magnetometer data covering descending phase of solar cycle 24 from the low latitude site Desalpar (DSP, L = 1.07). At CPL, the maximum number of Pc1 events is seen in the declining phase of the solar cycle 20 and minimum occurrence is observed in the ascending phase of the solar cycle 21. In contrast, at DSP, the Pc1 occurrence shows a maximum during solar maximum and a minimum in the declining phase of solar cycle 24. The annual and seasonal patterns of Pc1 occurrence show an inverse relation with sunspot numbers at both stations. The seasonal variation of Pc1 occurrence has a maximum in December solstice at CPL and in June solstice at DSP, respectively. The diurnal variations of Pc1 activity show similar trends at both locations with maximum Pc1 occurrence during pre- and post-midnight sectors. The superposed epoch analysis shows minimum number of Pc1s in the initial phase, followed by Pc1 occurrence in the main phase, increasing significantly in the recovery phase of geomagnetic storms. The role of ionospheric plasma density and attenuation of Pc1 waves upon propagation via the ionospheric waveguide is presented.

Alex magnetometer and telluric station in Egypt: First results on pulsation analysis

This study presents the first results of a newly installed ground-based station Alex Magnetometer and Telluric Station (AMTS) located in Alexandria governorate in Egypt (geographic coordinate: 30° 51.68′ N, 29° 33.67′ E). The station consists of a fluxgate digital magnetometer and a two-channel digital Long Period Telluric Recorder (LPTR). The station commenced operation on October 12th, 2021, by providing real-time data of the geoelectric and geomagnetic field components. Despite the low solar activity, the AMTS detected several signatures of geomagnetic storms. An illustrative case study was conducted on the strong geomagnetic storm of November 4th, 2021. The magnetic field components recorded by the station demonstrated a prompt increase synchronized with the Sudden Storm Commencement (SSC) captured by the ACE satellite arriving at 19:42 UT on November 3rd, 2021. The three geomagnetic field components recorded by the AMTS during the storm were consistent with the nearby INTERMAGNET stations. The digital fluxgate magnetometer’s high sampling frequency (400 Hz) and the LPTR with a sampling frequency (1 Hz), allowed us to capture all ULF pulsations. The structural pearl-shaped Pc1 pulsation was obtained in all phases of the geomagnetic storm with repetitive oscillations in the main storm phase. The wavelet analysis of micropulsations recorded at AMTS showed a high coherence with the nearby-four INTERMAGNET stations demonstrating high data integrity and reliability. The magnetometer and telluric measurements at the AMTS will fill the data gap in the northern section of Africa and allow us to study geoelectric and geomagnetic micropulsations in the region.

Airfoil Anemometer With Integrated Flexible Piezo-Capacitive Pressure Sensor

Demand is expected to accelerate for autonomous air vehicles that transport people and goods, making wind sensors on these vehicles and in the air space where they operate critical to ensure safe control of many simultaneous take-offs and landings. Conventional anemometers such as pitot tubes as well as rotating, heated-element, acoustic, and drag technologies have drawbacks for small and micro-aerial vehicles including high power consumption, high aerodynamic drag, complex signal processing, and high cost. This paper presents an airfoil-shaped anemometer that provides low drag while integrating sensors for measuring wind speed and direction on tethered kites, balloons, and drones. Wind speed is measured by an integrated dual-layer capacitive pressure sensor with a polyvinylidene fluoride (PVDF) diaphragm while wind direction is measured by a 3D digital magnetometer that senses the orientation of the airfoil relative to the earth’s magnetic field. A model is presented for a dual-layer capacitive sensor and validated through quasistatic pressure chamber testing. The capacitive sensor as well as a commercial digital magnetometer are integrated into a NACA 2412 profile airfoil and tested in a laboratory-scale wind tunnel. The capacitive sensor provides a sensitivity of 1.84 fF m2s−2 and the airfoil exhibits a unique stable angle-of-attack to within ±2° as measured by the magnetometer.

A new digital single-axis fluxgate magnetometer according to the cobalt-based amorphous effects.

Fluxgate sensors are currently widely used for weak magnetic field measurement because of their relatively great performance, such as resolution, power consumption, and measurement of vector magnetic fields directly. Since the analog fluxgate sensor has some drawbacks, e.g., it would be influenced by the noise of the analog circuit. Hence, in recent years, the analog circuit is gradually inclined to be realized by digital processing in which the software parameter adjustment is employed to replace the analog components, which can greatly improve the flexibility of the design. This paper proposes a digital single-axis fluxgate sensor according to the cobalt-based amorphous effect. To be specific, the analog signal output by the fluxgate is sampled directly by an analog-to-digital converter to obtain the signal waveform in digital form after amplification. The demodulation, filtering, and integration of the signal are all solved by mathematical algorithms. Based on the working principle of the fluxgate sensor, the selection of the magnetic core material and coil winding method of the fluxgate sensor probe is introduced in detail. The design and function of the excitation circuit and preamplifier circuit, as well as the specific realization of digital signal processing, are described. Finally, the performance test of the digital fluxgate sensor was performed under laboratory conditions, and the magnetic anomaly detection comparison experiment was performed outdoors with commercial fluxgate sensors. To sum up, the linearity of the digital single-axis fluxgate sensor is better than 1 × 10-5, and the root mean square noise value is below 0.1 nT. At the same time, it has good magnetic field tracking performance and is extremely sensitive to the magnetic field of the measurement area.

Characterization of a Digital AMR Magnetometer for Space Applications

In this article, we present research, development, calibration, and characterization of a novel concept of a digitally compensated, low-noise magnetometer based on anisotropic magnetoresistance sensors that is suitable for space applications. The main idea of the design was to reduce the number of precise analog components while using the digital signal processing power available in a modern microcontroller. Our most recent effort targeted lowering power consumption, enhancement of radiation hardness, and overall improvement of the parameters. The principle of operation is presented in detail, along with a detailed description of the instrumentation used to characterize the real instrument, including its noise, linearity, and temperature stability in the range of −20 °C to +70°C. The results of total ionizing dose (TID) testing at a gamma-ray irradiation facility are discussed at the complete magnetometer and part levels. This is an extended version of an article presented at I2MTC 2020 that contains the results of a second radiation test done with a slightly modified design. The instrument worked well throughout the entire irradiation session (TID of 1.05 kGy over 72 h), and the stability of main parameters was very good (50 pT/Gy offset and 1 ppm/Gy sensitivity stability).

The Experimental Albertan Satellite #1 (Ex-Alta 1) Cube-Satellite Mission

The Experimental Albertan satellite #1 (Ex-Alta 1) was a three-unit cube satellite (CubeSat) developed at the University of Alberta (UAlberta). As the first ‘made in Alberta’ spacecraft, the Ex-Alta 1 CubeSat was the Canadian contribution to the international QB50 CubeSat constellation mission ( www.qb50.eu ). Ex-Alta 1’s mission incorporated four science objectives, two technical objectives, and one educational outreach objective. These are reviewed in the context of the Ex-Alta 1 mission design, as well as future CubeSat constellation missions that may follow demonstration missions such as Ex-Alta 1 and the experiences of the QB50 project. In support of its objectives, Ex-Alta 1 flew the multi-needle Langmuir probe (m-NLP) QB50 standardized payload, a UAlberta developed miniaturized digital fluxgate magnetometer (DFGM) mounted on a two-element articulated deployable boom, a radiation dosimeter from Teledyne, and an open source onboard computer (OBC) developed at UAlberta. Ex-Alta 1 was released by a NanoRacks deployer from the International Space Station on May 26, 2017, and commanded and controlled from a ground-station developed and operated at UAlberta. Ex-Alta 1 operated continuously throughout its mission until it burned up in the atmosphere on November 14, 2018. The last two-way contact occurred on that day at 07:49:29 UTC, when the spacecraft reported an onboard temperature of 47 °C in eclipse at an altitude of 152 km and which marked the effective end of the mission. This paper provides an overview of the Ex-Alta 1 mission, its development, the spacecraft and mission design, and reports preliminary results from the payload focusing on the DFGM instrument. We also report briefly on related education and outreach activities, including the development and delivery of curriculum-targeted and CubeSat focused classroom sessions inspired by the Ex-Alta 1 mission to school pupils in Alberta.

Implementation of Interface Circuit for Digital SQUID with Sub-Flux Quantum Feedback Resolution

Digital SQUIDs with single flux quantum (SFQ) feedback have attracted much attention because of the feasibility of realizing a wide dynamic range and high slew rate for digital magnetometers. To achieve a higher resolution, we studied a digital SQUID with sub-flux quantum feedback. We studied implementation methods for an interface circuit by considering the circuit size, power consumption and signal processing to achieve high-resolution and highspeed operation of the digital SQUID magnetometer. Assuming the decimation filter and the up/down counter implemented on a FPGA board, a 1-bit to 16-bit deserializer with an output frequency of 500 MHz could be used for the interface circuit. The circuit scale was 1940 µm × 1720 µm, and the bias current was 302 mA. From the simulation results, a sufficient wide bias margin could be obtained up to 30 GHz.

Performance of Digital SQUID with Sub-Flux Quantum Feedback Resolution Fabricated using 10 kA/cm2 Nb Process

Digital superconducting quantum interference device (SQUID with Single Flux Quantum (SFQ) feedback operates as a Δ-type oversampling A/D converter. Magnetic flux resolution at Nyquist frequency can be improved by taking sub SFQ feedback resolution and large oversampling ratio. Using high critical current density Nb process for fabricating SFQ circuits, we expected more higher operation speed for the digital SQUID and resulting to higher magnetic flux resolutions. We expected a performance of the digital SQUID magnetometer fabricated using 10 kA/cm2 Nb process based on CAD layout, with an up/down counter using T2FF cells and parallel SFQ feedback. For the clock frequency of 13 GHz and the Nyquist frequency of 1.587 MHz, the magnetic field noise was lower than and the slew rate was exceeded 500 mT/s.

High-Resolution Digital SQUID Magnetometer using Sub-Flux Quantum Feedback

Digital SQUIDs with the single flux quantum (SFQ) feedback have attracted much attention because of the feasibility of realizing a wide dynamic range and high slew rate for digital magnetometers. In order to realize higher resolution, we have studied a digital SQUID with sub-flux quantum feedback. Combining the sub-flux quantum feedback to a feedback loop and the direct SFQ feedback to a main loop triggered by carry SFQ pulses from an up/down counter. In this study, we discuss the method of multi-flux quantum generation and compact design of the SFQ up/down counter for high-speed operation of the digital SQUID magnetometer.

Simple and Efficient Relaxation-Oscillator-Based Digital Techniques for Resistive Sensors — Design and Performance Evaluation

This article proposes simple relaxation-oscillator-based digital interfacing schemes for resistive sensors in single-element and quarter-bridge forms. The proposed interfaces, equipped with novel compensation techniques, render a direct-digital output proportional to sensor resistance. These interfaces offer many meritorious features, such as simplicity of design, nonrequirement of the reference voltage, lower execution time, and negligible influences from circuit nonidealities. The methodology of the interfaces and their design criteria and error analysis are described in this article. The first two interfaces are suitable for nonremote resistive sensors, while the third interface has been developed for remotely located resistive sensors. The functionality of the proposed interfaces has been verified using simulation as well as detailed experimental studies. The developed interfaces provide a linear direct-digital output, and the maximum experimental nonlinearity is merely 0.08%. Later, a representative sensor based on the giant magnetoresistance (GMR) phenomenon is selected, characterized, and tested with the developed interfaces. The complete instrumentation system is shown to act as a linear digital magnetometer. Finally, the performance of the developed interfaces is compared and shown to be better/comparable with respect to the existing works.

Some problems with old magnetic data processing

Continues magnetic measurements at the IKIR FEB RAS obser-vatories Magadan (MGD), Paratunka (PET), Yuzhno-Sakhalinsk (YSS), Cape Schmidt (CPS) and Khabarovsk (KHB) and CSIR-NGRI observatories Hyder-abad (HYB) and Choutuppal (CPL) have been started almost since their formation. A significant part of the results obtained is presented in the WDC and INTERMAGNET databases. However, a large amount of raw data remains un-processed and unavailable for using by scientific community. In the past few years, institutes has been making efforts to process and reprocess old magnetic data. Digital images of analog magnetograms of the Observatory Paratunka since 1967 were obtained and the possibility of their use for calculation hourly and minute values of magnetic field elements was evaluated. Old digital data that was available during the conversion from analog to digital magnetometers is processed. The main problem of processing or re-processing archived data is the lack of information (metadata) about the measurement conditions. First of all, these are the results of absolute observations, which are necessary to obtain the values of the elements of the total field vector. In this paper, some technologies are proposed that allow to use the data obtained during processing of analog magnetograms to adjust the digital magnetometers records. A signif-icant problem is the lack or inaccuracy of information about the temperature conditions in the variation pavilion, about magnetometers or support equipment maintenance or about works in and near the pavilions. As we accumulate the experience during the processing of old magnetic data, a “catalog” of noise and its typical images is formed. This makes it more reliable and efficient to identify and remove this noise from records.

Calibration of Off-the-Shelf Anisotropic Magnetoresistance Magnetometers.

Magnetometers based on the anisotropic magnetoresistive effect are used in many applications for orientation determination, by measuring the magnetic field of the Earth. As sensors of this type are commercial, off-the-shelf components, manufacturers provide limited information on their measurement performance. Therefore, we present a (to date) unprecedented comprehensive calibration study on three state-of-the-art digital anisotropic magnetoresistance magnetometers, to precisely determine various performance parameters and stability across different sensors of the same model. With the evaluation of sensitivity, noise, offset, and orientation determination, as well as considering dependencies on temperature and frequency, the performance of each sensor can be improved significantly, enabling their implementation in demanding fields of application (such as in satellites). Different measurement and calibration techniques, specifically aimed at the characteristics of the examined magnetometers, were utilized, using a sophisticated magnetic laboratory that has served as a calibration facility for several interplanetary space missions. Our study allows operators to decide whether to consider anisotropic magnetoresitance magnetometers for their application and, more importantly, to be able to (at least partially) skip a time-intensive and complicated calibration by using the sensor parameters given in this paper. To that end, the most promising sensor is recommended. The sensor examination suggests a good comparability of different sensors of the same model, and shows the importance of noise regarding the sensor performance with a noise floor up to 124 nT/ at 1 Hz. Additionally, depending on the sensor model, the sensitivity is 14 nT at best, and the attitude determination error can be reduced to about 0.3° with the given calibration.

Influence of Ba Substitutions on Microstructure and Magnetic Properties of La–Ca–Co System Permanent Ferrite

La0.6Ca0.4−xBaxO⋅n/2(Fe1−yCoy)2O3(x = 0, 0.05, 0.1, 0.15 and 0.2) permanent ferrite materials were prepared by ceramic technique. The topography and the structure were characterized by scanning electron microscopy (SEM) and x-ray diffraction (XRD), respectively. The magnetic properties were measured using vibrating sample magnetometer (VSM) and digital magnetometer. Single M-phase and flake-like grains were obtained for samples without Ba substitution(x = 0), and the magnetic properties of the pre-sintering La–Ca–Co ferrite were as follows: Br = 440 mT, Hcb = 296 kA/m, Hcj = 426 kA/m, (BH)max = 36.6 kJ/m3 and Hk/Hcj = 0.83. When Ca was substituted by Ba, pre-sintered powder presents single M-phase structure and close three-dimensional size of grains, resulting in an improved rectangle ratio of sintered magnet. The rectangle ratio of sintered magnet reaches a maximum of 0.93 when x = 0.1. By optimizing process parameters, M-type La–Ca–Ba–Co sintered magnet was prepared with Br = 445 mT, Hcb = 337 kA/m, Hcj = 420 kA/m, (BH)max = 38.6 kJ/m3 and Hk/Hcj = 0.95.

Effect of second harmonic in pulse-width-modulation-based DAC for feedback of digital fluxgate magnetometer

Digital fluxgate magnetometers employ processing of the measured pickup signal to produce the value of the compensation current. Using pulse-width modulation with filtering for digital to analog conversion is a convenient approach, but it can introduce an intrinsic source of nonlinearity, which we discuss in this design note. A code shift of one least significant bit changes the second harmonic content of the pulse train, which feeds into the pick-up signal chain despite the heavy filtering. This effect produces a code-dependent nonlinearity. This nonlinearity can be overcome by the specific design of the timing of the pulse train signal. The second harmonic is suppressed if the first and third quarters of the excitation period pulse train are repeated in the second and fourth quarters. We demonstrate this principle on a digital magnetometer, achieving a magnetometer noise level corresponding to that of the sensor itself.

Science objectives of the magnetic field experiment onboard Aditya-L1 spacecraft

The Aditya-L1 is first Indian solar mission scheduled to be placed in a halo orbit around the first Lagrangian point (L1) of Sun-Earth system in the year 2018–19. The approved scientific payloads onboard Aditya-L1 spacecraft includes a Fluxgate Digital Magnetometer (FGM) to measure the local magnetic field which is necessary to supplement the outcome of other scientific experiments onboard. The in-situ vector magnetic field data at L1 is essential for better understanding of the data provided by the particle and plasma analysis experiments, onboard Aditya-L1 mission. Also, the dynamics of Coronal Mass Ejections (CMEs) can be better understood with the help of in-situ magnetic field data at the L1 point region. This data will also serve as crucial input for the short lead-time space weather forecasting models.The proposed FGM is a dual range magnetic sensor on a 6 m long boom mounted on the Sun viewing panel deck and configured to deploy along the negative roll direction of the spacecraft. Two sets of sensors (tri-axial each) are proposed to be mounted, one at the tip of boom (6 m from the spacecraft) and other, midway (3 m from the spacecraft). The main science objective of this experiment is to measure the magnitude and nature of the interplanetary magnetic field (IMF) locally and to study the disturbed magnetic conditions and extreme solar events by detecting the CME from Sun as a transient event. The proposed secondary science objectives are to study the impact of interplanetary structures and shock solar wind interaction on geo-space environment and to detect low frequency plasma waves emanating from the solar corona at L1 point. This will provide a better understanding on how the Sun affects interplanetary space.In this paper, we shall give the main scientific objectives of the magnetic field experiment and brief technical details of the FGM onboard Aditya-1 spacecraft.

Sensor module for testing magnetometric borehole inclinometers under field conditions

The paper presents the testing procedure and the test unit for borehole inclinometers using a reference system of orientation incorporated in the sensor module. Computational algorithms are developed for azimuth, zenith and apsidal angles. The estimated error is obtained for the detection of zenith angles. The sensor module uses the Honeywell HMS1053, a digital resistance magnetometer and the Colibrys MS9000 accelerometer. The size and weight of the test unit are rather small that provides its easy transportation. The test unit is universal as it can be used for inclinometers with different casing diameters. The cost of the test unit is much lower than that of the stationary one. Easy servicing reduces the labor content during the inclinometer in situ testing.

A scalable decimation filter ASIC for high resolution digital magnetometer with sigma-delta modulator feedback loop

High-resolution digital magnetometers often use sigma-delta modulator feedback loops for large dynamic range, good linearity and low power consumption. A decimation filter is usually needed to obtain the high-resolution output data and reduce the output data rate at the same time. A scalable decimation filter application specific integrated circuit (ASIC) for high-resolution digital magnetometer with sigma-delta modulator feedback loop has been designed, implemented and fabricated. Keeping the decimation ratio of 128 to 1 fixed, the ASIC chip was carefully designed to be scaled with input data rate accordingly, thus maintaining the same resolution of 24 bits for the digital magnetometer. The ASIC chip consists of a cascaded integrator-comb (CIC) filter decimated by 16, a droop compensation programmable FIR1 filter decimated by 4, a brick-wall programmable FIR2 filter decimated by 2 and a 5th order sigma-delta bit stream generator for built-in-self-testing (BIST). The chip was designed and fabricated based on the GlobalFoundries 0.18µm CMOS process. Its total die size is about 3×3mm2, having 256,000 equivalent logic gates. In a typical working scenario with an input data rate of 128kHz, the measured power consumption of the core powered with 1.8V is about 0.9mW.

Loud and clear: Characterization of particle motion in Humpback whale song and its potential role in communication

Acoustic communication can rapidly transfer a substantial amount of information, yet emitted signals must be conveyed with enough clarity to allow appropriate responses. Many mysticete calls such as humpback whale (Megaptera novaeangliae) song can be detected over large distances as a result of the propagating acoustic pressure wave, yet little is known regarding the particle motion component of these signals. To explore the particle velocity of humpback whale song, three singing whales were recorded from a vessel off Maui, HI in March 2015, using a sensor that contained a digital magnetometer, tri-axial accelerometer, and an omnidirectional hydrophone. The median magnitude of the acoustic particle velocity signal was substantial (64.5 dB re: 1m/s) for song components with a median pressure of 135.4 dB re: 1μPa. As vessel and sensor gradually drifted away or toward the whales, acoustic particle velocity and sound pressure correspondingly decreased or increased (range: 49.3-77.9 dB re: 1m/s and 118.4-148.1 dB re: 1μPa). The particle velocity signals were high even at 200m from the whale indicating this cue is substantial well into the far-field. There were predictable trends in the acoustic particle motion signal component and this component of song is a cue available to nearby animals.