Contactless measurement of electric current using magnetic sensors

We review recent advances in magnetic sensors for DC/AC current transducers, especially novel AMR sensors and integrated fluxgates, and we make critical comparison of their properties. Most contactless electric current transducers use magnetic cores to concentrate the flux generated by the measured current and to shield the sensor against external magnetic fields. In order to achieve this, the magnetic core should be massive. We present coreless current transducers which are lightweight, linear and free of hysteresis and remanence. We also show how to suppress their weak point: crosstalk from external currents and magnetic fields

A Magnetic Distance Sensor with High Precision

A magnetic distance sensor working at very low frequency has been developed to measure distances up to 1 m. The principle is similar to that of the 3-D magnetic tracker, but the system is optimized to minimize the error in distance for static measurements. The system is not affected by conductive objects. The uncertainty caused by noise and interference is below 2 mm, even in a noisy environment. The measurement time of 3 min can be decreased to 1 min, depending on the amplitude of the interferences and the required accuracy. After applying corrections, systematic error of 5 mm was achieved by using a calibration model. The system is scalable up to 20 m range

Metal Detector Signal Imprints of Detected Objects

Humanitarian de-mining missions are activities in which an operator safety and time consumption are key issues. To increase a discrimination ability of ATMID metal detector, which we have been using, we extended the capability of the detector with mounting Inertial Measurement Unit (IMU) supplemented by two optical distance sensors on the detector head. That enabled us to perform dead reckoning based on accelerations and angular rates measured by IMU in all three axes. Optical distance sensors have been used for compensation purposes and an initial distance measurement. Our main aim was to interconnect magnetic imprint sensed by the detector with precise localization of its head, which led to imprint size estimation as well as its position. Due to low-cost MEMS (Micro-Electro-Mechanical System) based IMU implementation we have had to deal with unstable dead reckoning outcomes. For this reason we used our designed Complex Magnetic Markers (CMMs) which demarked a searched area plus provided us with precise positioning at its both edges. The main contribution of this paper is in the study and identification of CMM magnetic imprints characteristics and their differences related to various aspects of CMM usage during de-mining procedure and its conditions. The characteristics of CMMs have been studied and analyzed according to several laboratory experiments and results are presented

Kaons and pions in strange quark matter

The behavior of kaons and pions in strange quark matter in weak equilibrium, is investigated within the SU(3) Nambu-Jona-Lasinio [NJL] model. This work focuses a region of high densities where the behavior of mesons has not been explored in the framework of this model. It is found that above the density where strange valence quarks appear in the medium, $\rho = 3.8 \rho_0$, a change of behavior of different observables is observed indicating a tendency to the restoration of flavor symmetry. In particular, the splitting between charge multiplets, $K^+, K^-; K^0, {\bar K^0} {and} \pi^+, \pi^-$ decrease and the low energy modes with quantum numbers of $K^-, \bar K^0 {and} \pi^+$, which are excitations of the Fermi sea, are less relevant than for lower densities.Comment: 10 pages, 3 figures included; revised version, some changes in the discussio

Tester for space micro-accelerometer

AbstractMicro-accelerometer MAC04 has been developed in order to measure very low accelerations such as those caused to satellites by atmospheric drag and other non-gravitational forces. The instrument uses a cubic proof-mass inside a small cavity. In an open loop the change of capacitance between the cube and 12 electrodes on the inner cavity surface is a measure of the applied acceleration. It is very difficult to ground test and calibrate such a device due to gravity. The tester simulates the change of capacitances (base capacitance 13,5pF, changes in a range of ±1.5pF). Complete closed loop system is presented

Eddy current speed sensor with magnetic shielding

This paper presents the design and analysis of a new eddy current speed sensor with ferromagnetic shielding. Aluminum and solid iron are considered for the moving part. One excitation coil and two antiserially connected pick up coils are shielded by a thin steel lamination. 3D time stepping finite element analysis is used to analyze the sensor performance with different magnetic materials and compare with experimental results. The compactness, simplicity and excellent linearity with different magnetic materials for the moving part show uniqueness of the proposed speed sensor. The shielding increases sensitivity and reduces the influence of close ferromagnetic objects and interferences on the sensor performance

Transformer position sensor for a pneumatic cylinder

A novel transformer-based sensor for a pneumatic cylinder enables measurements of the piston position to be made through a thick conductive cylinder. Unlike existing industrial solutions, which are mainly based on a moving magnet, our sensors do not require modifications to the parts inside the cylinder

Self-consistent symmetries in the proton-neutron Hartree-Fock-Bogoliubov approach

Symmetry properties of densities and mean fields appearing in the nuclear Density Functional Theory with pairing are studied. We consider energy functionals that depend only on local densities and their derivatives. The most important self-consistent symmetries are discussed: spherical, axial, space-inversion, and mirror symmetries. In each case, the consequences of breaking or conserving the time-reversal and/or proton-neutron symmetries are discussed and summarized in a tabulated form, useful in practical applications.Comment: 26 RevTex pages, 1 eps figure, 9 tables, submitted to Physical Review

Are There Diquarks in the Nucleon?

This work is devoted to the study of diquark correlations inside the nucleon. We analyze some matrix elements which encode information about the non-perturbative forces, in different color anti-triplet diquark channels. We suggest a lattice calculation to check the quark-diquark picture and clarify the role of instanton-mediated interactions. We study in detail the physical properties of the 0+ diquark, using the Random Instanton Liquid Model. We find that instanton forces are sufficiently strong to form a diquark bound-state, with a mass of ~500 MeV, which is compatible with earlier estimates. We also compute its electro-magnetic form factor and find that the diquark is a broad object, with a size comparable with that of the proton.Comment: Final version, accepted for publication on Phys. Rev.

Computing the Effective Hamiltonian of Low-Energy Vacuum Gauge Fields

A standard approach to investigate the non-perturbative QCD dynamics is through vacuum models which emphasize the role played by specific gauge field fluctuations, such as instantons, monopoles or vortexes. The effective Hamiltonian describing the dynamics of the low-energy degrees of freedom in such approaches is usually postulated phenomenologically, or obtained through uncontrolled approximations. In a recent paper, we have shown how lattice field theory simulations can be used to rigorously compute the effective Hamiltonian of arbitrary vacuum models by stochastically performing the path integral over all the vacuum field fluctuations which are not explicitly taken into account. In this work, we present the first illustrative application of such an approach to a gauge theory and we use it to compute the instanton size distribution in SU(2) gluon-dynamics in a fully model independent and parameter-free way.Comment: 10 pages, 4 figure