Electromagnetic Near Field Array
French translation: champ proche multiéléments ou NFA
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| 10:33 Sep 19, 2019 |
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| English to French translations [PRO] Tech/Engineering - Engineering (general) / Non destructive testing | |||||||
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|  Selected response from: Johannes Gleim Local time: 01:32 | ||||||
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| Discussion entries: 8 | |
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45 mins confidence: 
| electromagnetic near field array réseau (matrice) de champ proche de rayonnement électromagnétique Explanation: https://tel.archives-ouvertes.fr/tel-00952974/document |
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| electromagnetic near field array courants de Foucault champ proche multiéléments Explanation: ECT = Eddy Current Testing = méthode électromagnétique de contrôle non destructif cf. https://www.eddyfi.com/technologies/near-field-array-nfa/ https://www.eddyfi.com/fr/technologies/champ-proche-multiele... https://www.ndt.net/article/cofrend2017/papers/MA2A1_A_RAUDE... |
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| electromagnetic near field array champ proche multiéléments ou NFA Explanation: The near field and far field are regions of the electromagnetic field (EM) around an object, such as a transmitting antenna, or the result of radiation scattering off an object. Non-radiative 'near-field' behaviours of electromagnetic fields dominate close to the antenna or scattering object, while electromagnetic radiation 'far-field' behaviours dominate at greater distances. Far-field E (electric) and B (magnetic) field strength decreases inversely with distance from the source, resulting in an inverse-square law for the radiated power intensity of electromagnetic radiation. By contrast, near-field E and B strength decrease more rapidly with distance: part decreases by the inverse-distance squared, the other part by an inverse cubed law, resulting in a diminished power in the parts of the electric field by an inverse fourth-power and sixth-power, respectively. The rapid drop in power contained in the near-field ensures that effects due to the near-field essentially vanish a few wavelengths away from the radiating part of the antenna. https://en.wikipedia.org/wiki/Near_and_far_field Near-field testing (NFT) is a technique commonly used to inspect air coolers and ferromagnetic heat exchanger tubing. : Near-field array (NFA) technology represents a unique alternative for this application. It provides scan results in the form of intuitive C-scan imaging, offers better sensitivity over other inspection methods, and is much faster. The development of NFA posed an impressive technical challenge, especially in terms of multiplexing and probe design. https://ndtlibrary.asnt.org/2015/NearFieldArrayTechnologyThe... wave interrogated near field array system and method for detection of subwavelength scale anomalies système et procédé de réseau en champ proche à interrogation par ondes pour détection d'anomalies à une échelle sublongueur d'onde https://context.reverso.net/traduction/anglais-francais/near... Near-field array (NFA) is the multiplexed evolution of near-field testing (NFT). : NFA technology functions in transmit-receive mode. A single bobbin coil acts as the transmitter to generate the near field, an absolute bobbin receiver coil detects and sizes the general internal wall loss, and up to two rows of multiplexed receiver coils cover the entire inner surface of aluminum-finned tubes (full 360°). With up to 30 optimized coils and thanks to channel multiplexing, NFA is capable of generating high-quality signals yielding a very good signal-to-noise ratio (SNR) that allow detecting circumferential and axial cracking. https://www.eddyfi.com/technologies/near-field-array-nfa/ Eddyfi a bonifié la technologie des sondes champ proche grâce à une matrice de bobines multiplexées. C’est ce qu’on appelle le champ proche multiéléments, une technique spécialement conçue pour contrôler efficacement les tubes à ailettes d’aluminium et les échangeurs de chaleur ferromagnétiques. : Nos sondes NFA sont en mesure de détecter les défauts les plus communs dans ces tubes comme les piqûres internes, la fissuration interne aux plaques tubulaires, l’érosion interne et l’amincissement des parois. https://www.eddyfi.com/fr/produits/sondes-champ-proche-multi... Fiche de produit sondes champ proche multiéléments (anglais) https://manualzz.com/doc/13999537/fiche-de-produit-sondes-ch... Introduction aux propriétés et mesures des rayonnement HF .. : La distance de transition entra la zone de champ proche et de champ lointain est déterminée exactement, à des distances • à 27 MHz de +- 27 meters • à 270 MHz de +- 2.7 meters • à 2700 MHz de +- 0.27 meters Cela signifie que les distances sont inversement proportionnelle aux fréquences Remarque : En champ proche, les champs électriques et magnétiques de haute fréquences doivent se mesurent séparément en V/m e A/m. Il n’est pas possible dans ce cas de calculer l’un par rapport à l’autre et vice versa. Par contre en champ éloignée, c’est possible. On doit mesurer la densité de puissance an mW/m² or µW/m. https://www.google.de/url?sa=t&rct=j&q=&esrc=s&source=web&cd... -------------------------------------------------- Note added at 3 hrs (2019-09-19 13:37:14 GMT) -------------------------------------------------- This is quite different from NLA technology, which uses electromagnetic waves rather than eddy currents (ECA). Inspection of stainless steel heat exchanger tube with eddy current array probe : The DefHi eddy current array probe provides several benefits for non-ferrous tubing inspection: www.eddyfi.com/wp-content/uploads/2014/04/inspection-stainl... Lorsqu’il s’agit de contrôler des tubes d’un condenseur ou tout autre faisceau tubulaire, en maintenance, om pense tout de suite aux Courant de Foucault. Sonde CF mulitéléments FIGURE 1 : Configuration des tubes à contrôler : Paramètre d’essais Dans le cas présent 3 fréquences sont injectées dans la sonde : 400, 250 et 100 kHz. www.eddyfi.com/wp-content/uploads/2014/08/etude-de-cas-cour... Note: this frequency is much lower than that used for NFA. Near-Field Array Probes www.eddyfi.com/wp-content/uploads/2016/12/specifications-sh... EDDY CURRENT ARRAY ECA technology used many individual coils, grouped in one probe … https://www.eddyfi.com/wp-content/uploads/2018/10/eddyfi-sur... And, last but not least, eddy currents are different from electromagnetic waves. -------------------------------------------------- Note added at 3 hrs (2019-09-19 13:39:44 GMT) -------------------------------------------------- Correction: eddy Current Arrays (ECA) technology differs from Near Field Arrays (NFA) by using electromagnetic waves rather than eddy currents. -------------------------------------------------- Note added at 22 hrs (2019-09-20 09:12:08 GMT) -------------------------------------------------- Eddy currents (also called Foucault's currents) are loops of electrical current induced within conductors by a changing magnetic field in the conductor according to Faraday's law of induction. Eddy currents flow in closed loops within conductors, in planes perpendicular to the magnetic field. They can be induced within nearby stationary conductors by a time-varying magnetic field created by an AC electromagnet or transformer, for example, or by relative motion between a magnet and a nearby conductor. The magnitude of the current in a given loop is proportional to the strength of the magnetic field, the area of the loop, and the rate of change of flux, and inversely proportional to the resistivity of the material. https://en.wikipedia.org/wiki/Eddy_current Eddy-current testing (also commonly seen as eddy current testing and ECT) is one of many electromagnetic testing methods used in nondestructive testing (NDT) making use of electromagnetic induction to detect and characterize surface and sub-surface flaws in conductive materials. In its most basic form — the single-element ECT probe — a coil of conductive wire is excited with an alternating electrical current. This wire coil produces an alternating magnetic field around itself. The magnetic field oscillates at the same frequency as the current running through the coil. When the coil approaches a conductive material, currents opposite to the ones in the coil are induced in the material — eddy currents. Variations in the electrical conductivity and magnetic permeability of the test object, and the presence of defects causes a change in eddy current and a corresponding change in phase and amplitude that can be detected by measuring the impedance changes in the coil, which is a telltale sign of the presence of defects. https://en.wikipedia.org/wiki/Eddy-current_testing The Near-Field-Technology was already described in my first reference. You will easily recognize the quite different measuring principles: eddy currents induced by alternating magnetic fields vs. electromagnetic fields (RF) consisting of magnetic and electrical fields. Radio frequency (RF) is the oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency range from around twenty thousand times per second (20 kHz) to around three hundred billion times per second (300 GHz). https://en.wikipedia.org/wiki/Radio_frequency In physics, electromagnetic radiation (EM radiation or EMR) refers to the waves (or their quanta, photons) of the electromagnetic field, propagating (radiating) through space, carrying electromagnetic radiant energy.[1] It includes radio waves, microwaves, infrared, (visible) light, ultraviolet, X-rays, and gamma rays. https://en.wikipedia.org/wiki/Electromagnetic_radiation You will easily recognized the different principles: eddy currents induced by alternating electromagnetic fields vs. radio frequencies consisting of electric fields alternating with magnetic fields. |
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