scholarly journals Soft and Hard Iron Compensation for the Compasses of an Operational Towed Hydrophone Array without Sensor Motion by a Helmholtz Coil

Sensors ◽  
2021 ◽  
Vol 21 (23) ◽  
pp. 8104
Author(s):  
Tommaso Lapucci ◽  
Luigi Troiano ◽  
Carlo Carobbi ◽  
Lorenzo Capineri
Keyword(s):  
Magnetic Field ◽  
Geomagnetic Field ◽  
Calibration Procedure ◽  
Helmholtz Coil ◽  
Bearing Estimation ◽  
Field Uniformity ◽  
Standard Calibration ◽  
Commercial Off The Shelf ◽  
Set Up ◽  
Hydrophone Array

Usually, towed hydrophone arrays are instrumented with a set of compasses. Data from these sensors are utilized while beamforming the acoustic signal for target bearing estimation. However, elements of the hydrophone array mounted in the neighborhood of a compass can affect the Earth’s magnetic field detection. The effects depend upon the materials and magnetic environment present in the vicinity of the platform hosting the compass. If the disturbances are constant in time, they can be compensated for by means of a magnetic calibration procedure. This process is commonly known as soft and hard iron compensation. In this paper, a solution is presented for carrying out the magnetic calibration of a COTS (Commercial Off the Shelf) digital compass without sensor motion. This approach is particularly suited in applications where a physical rotation of the platform that hosts the sensor is unfeasible. In our case, the platform consists in an assembled and operational towed hydrophone array. A standard calibration process relies on physical rotation of the platform and thus on the use of the geomagnetic field as a reference during the compensation. As a variation on this approach, we generate an artificial reference magnetic field to simulate the impractical physical rotation. We obtain this by using a tri-axial Helmholtz coil, which enables programmability of the reference magnetic field and assures the required field uniformity. In our work, the simulated geomagnetic field is characterized in terms of its uncertainty. The analysis indicates that our method and experimental set-up represent a suitably accurate approach for the soft and hard iron compensation of the compasses equipped in the hydrophone array under test.

scholarly journals Soft and Hard Iron Compensation for the Compasses of an Operational Towed Hydrophone Array without Sensor Motion by a Helmholtz Coil

2021 ◽  
Author(s):  
Tommaso Lapucci ◽  
Luigi Troiano ◽  
Carlo Carobbi ◽  
Lorenzo Capineri
Keyword(s):  
Magnetic Field ◽  
Geomagnetic Field ◽  
Helmholtz Coil ◽  
The Earth ◽  
Bearing Estimation ◽  
Field Uniformity ◽  
Standard Calibration ◽  
Commercial Off The Shelf ◽  
Set Up ◽  
Hydrophone Array

Usually, towed hydrophone arrays are instrumented with a set of compasses. Data from these sensors are utilized while beamforming the acoustic signal for target bearing estimation. However, elements of the hydrophone array mounted in the neighborhood of a compass can affect the Earth’s magnetic field detection. The effects depend upon the kind of elements present in the platform hosting the compass. If the disturbances are constant in time, they can be compensated for by means of a magnetic calibration. This process is commonly known as soft and hard iron compensation. In this paper, a solution is presented to carry out the magnetic calibration of a COTS (Commercial Off The Shelf) digital compass without unattainable sensor motion. This approach is particularly suited in applications where a physical rotation of the platform that hosts the sensor is unfeasible. In our case, the platform consists in an assembled and operational towed hydrophone array. A standard calibration process relies on physical rotation of the platform and thus on the use of the geomagnetic field as a reference during the compensation. As a variation on this approach, we provide to the sensor an artificial reference magnetic field to simulate the unfeasible physical rotation. We obtain this by using a tri-axial Helmholtz coil, which enables programmability of the reference magnetic field and assures the required field uniformity. In our work, the simulated geomagnetic field is characterized in terms of its uncertainty. The analysis indicates that our method and experimental set-up represent a suitably accurate approach for the soft and hard iron compensation of the compasses equipped in the hydrophone array under test.

Magnetic Field Uniformity around Near‐Helmholtz Coil Configurations

1969 ◽  
Vol 40 (11) ◽  
pp. 1468-1470 ◽  
Author(s):  
R. K. Cacak ◽  
J. R. Craig
Keyword(s):  
Magnetic Field ◽  
Helmholtz Coil ◽  
Field Uniformity

Effect of Purging Rate on the Calibration of Dew Point Sensor and the Estimation of Measurement Uncertainty

2014 ◽  
Vol 627 ◽  
pp. 161-167 ◽  
Author(s):  
Yun Kyung Bae ◽  
Dong Hoon Hyun
Keyword(s):  
Measurement Uncertainty ◽  
Calibration Procedure ◽  
Standard Uncertainty ◽  
International Standards ◽  
Dew Point ◽  
Measurement Condition ◽  
Testing Laboratory ◽  
Standard Calibration ◽  
Set Up ◽  
Uncertainty Source

The purpose of this paper is to study the effect of purging rate on calibration or test of the dew point sensors and estimation of measurement uncertainty. The measurement is carried out to analyze the variation on measured dew point temperatures for the sample dew point sensors (DPS) due to various durations of purge by using calibrated standard chilled mirror hygrometer. To set up measurement condition, the whole measurement system were kept in the state of purging for 3 hours, 15 hours, 65 hours, 140 hours, 200 hours. The dew point temperatures were measured in the range from-50 °C to 10 °C. In order to investigate the effect of purging rate as an uncertainty source on the measurement uncertainty, the contributions to the standard uncertainty for purging rate were also estimated due to reference dew point temperatures. The measurement was conducted according to standard calibration procedure of Korea Testing Laboratory which assures suitability and traceable results. It is also based on international standards.

Calibration Procedure for Magnetization Loop Tracers

2013 ◽  
Vol 543 ◽  
pp. 472-475
Author(s):  
Vasiliki Roussi ◽  
Clio G. Vossou
Keyword(s):  
Magnetic Field ◽  
Coming Out ◽  
Calibration Procedure ◽  
The Finite Element Method ◽  
Vertical Array ◽  
Steel Sheets ◽  
Excitation Coil ◽  
Set Up ◽  
Electrical Steel Sheets ◽  
The Magnetic Field

The purpose of this paper is to calibrate the magnetic field coming out of an excitation coil of certain specifications, fabricated for non-destructing testing of electrical steel sheets. Thus, a comparison between experimental and numerical analysis is discussed. For the experimental estimation of the magnetic field, a sensitive Hall sensor is used to measure the dc field at a vertical array of three selected points inside the coil. These are the lower, the middle and the upper point of the coil cross section, respectively. The magnetic field is then computed theoretically using the finite element method and the BiotSavart law. Measured results are in agreement with the calculated results of the excitation field very well, within the limits of our experimental set-up.

scholarly journals Predictions of the geomagnetic secular variation based on the ensemble sequential assimilation of geomagnetic field models by dynamo simulations

2020 ◽  
Vol 72 (1) ◽  
Author(s):  
Sabrina Sanchez ◽  
Johannes Wicht ◽  
Julien Bärenzung
Keyword(s):  
Magnetic Field ◽  
Secular Variation ◽  
Geomagnetic Field ◽  
Wave Number ◽  
Main Magnetic Field ◽  
Candidate Model ◽  
Uncertainty Estimates ◽  
Geomagnetic Field Models ◽  
Dipole Configuration

Abstract The IGRF offers an important incentive for testing algorithms predicting the Earth’s magnetic field changes, known as secular variation (SV), in a 5-year range. Here, we present a SV candidate model for the 13th IGRF that stems from a sequential ensemble data assimilation approach (EnKF). The ensemble consists of a number of parallel-running 3D-dynamo simulations. The assimilated data are geomagnetic field snapshots covering the years 1840 to 2000 from the COV-OBS.x1 model and for 2001 to 2020 from the Kalmag model. A spectral covariance localization method, considering the couplings between spherical harmonics of the same equatorial symmetry and same azimuthal wave number, allows decreasing the ensemble size to about a 100 while maintaining the stability of the assimilation. The quality of 5-year predictions is tested for the past two decades. These tests show that the assimilation scheme is able to reconstruct the overall SV evolution. They also suggest that a better 5-year forecast is obtained keeping the SV constant compared to the dynamically evolving SV. However, the quality of the dynamical forecast steadily improves over the full assimilation window (180 years). We therefore propose the instantaneous SV estimate for 2020 from our assimilation as a candidate model for the IGRF-13. The ensemble approach provides uncertainty estimates, which closely match the residual differences with respect to the IGRF-13. Longer term predictions for the evolution of the main magnetic field features over a 50-year range are also presented. We observe the further decrease of the axial dipole at a mean rate of 8 nT/year as well as a deepening and broadening of the South Atlantic Anomaly. The magnetic dip poles are seen to approach an eccentric dipole configuration.

Humanity Imperiled by the Geomagnetic Field and Human Corruption

2021 ◽  
Vol 8 (1) ◽  
pp. 456-478
Author(s):  
J. Marvin Herndon
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Charged Particle ◽  
Geomagnetic Field ◽  
Paradigm Shift ◽  
Government Officials ◽  
The Public ◽  
Person Perspective ◽  
First Person Perspective ◽  
The Many

Earth’s magnetic field acts as a shield, protecting life and our electrically-based infrastructure from the rampaging, charged-particle solar wind. In the geologic past, the geomagnetic field has collapsed, with or without polarity reversal, and inevitably it will again. The potential consequences of geomagnetic collapse have not only been greatly underestimated, but governments, scientists, and the public have been deceived as to the underlying science. Instead of trying to refute or advance a paradigm shift that occurred in 1979, global geoscientists, individuals and institutions, chose to function as a cartel and continued to promote their very-flawed concepts that had their origin in the 1930s and 1940s, consequently wasting vast amounts of taxpayer-provided research money, and making no meaningful advances or understanding. Here, from a first person perspective, I describe the logical progression of understanding from that paradigm shift, review the advances made and their concomitant implications, and touch upon a few of the many efforts that were made to deceive government officials, scientists, and the public. It is worrisome that geoscientists almost universally have engaged in suppressing or ignoring sound scientific advances, including those with potentially adverse implications for humanity. All of this suggests that the entire institutional structure of the geophysical sciences, funding, institutions, and bureaucracies should be radically reformed.

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