Magnetic Shield Effectiveness in Low Frequency

Abstract

Abstract-Since the early days of radio and telegraph communications, it has been known that a spark gap generates electromagnetic waves rich in spectral content (frequency components) and that these waves can cause interference or noise in various electronic and electrical devices such as radio receivers and telephone communications. Electromagnetic pulses are fields of energy that they can damage electrical and electronic circuits at once. New technology of microelectronic circuits is sensitive to interference power. An intentional or inadvertent risk and unforeseen create irreparable damages, so that it is important to investigate electromagnetic interference from viewpoint: generation source, the effectiveness on electronic components and safekeeping methods. One of the prevalent methods for safekeeping against these pulses is shielding. In this paper, at first, the effect of magnetic field intensity is investigated in frequency selected (0-545Hz) for various shields such as: paramagnetic materials, diamagnetic materials and ferromagnetic materials and shielding effectiveness is calculated for various low frequencies in one point in shield and shielding effectiveness variation with increase in frequency for any material is obtained. In The following of paper, the effect of magnetic field intensity is investigated on shield's two apertures and six apertures. Then, the apertures are displaced on shield surface and shielding effectiveness variation is obtained. This apertures displacement has done for various shield materials. Finally, the effects of composite shields are studied to shielding effectiveness. These shields have combined to two materials. We obtained interesting results from composite shields. In this paper, solution method has chosen 2DFEM and the whole of simulations have done Cosmos/M. Index Terms-Shielding effectiveness, Helmholtz coil, paramagnetic material, diamagnetic material, ferromagnetic material, low frequency.

Precision measurement and suppression of low-frequency noise in a current source with double-resonance alignment magnetometers

“…[20] The magnetic shielding material we used is permalloy, which has high shielding performance against lowfrequency noise. [21] The magnetic shielding coefficient of our two systems is about 1 × 10 6 for DC magnetic fields and AC magnetic fields above 1 Hz. As for the geomagnetic drift of about 200 nT/day, while the shielding coefficient for low frequencies will decrease, it is still in the order of 10 4 .…”

Estudio de blindaje magnético en materiales conductores en función de la frecuencia.

“…Cabe destacar que se realizó el análisis para el hierro a partir de los datos tomados del laboratorio y comparados con los obtenidos en el análisis teórico y en las simulaciones, donde no se observa que la permeabilidad alcanza su máximo valor; razón por la cual los resultados para este material discrepan para cada uno de los análisis [10,11]. En la figura 2 se observa cómo la eficiencia del cobre tiene un comportamiento creciente hasta cerca de los 50.000 Hz, punto en el cual empieza a descender levemente hasta llegar a los 100.000 Hz; este comportamiento se debe al efecto piel producido por las altas frecuencias a las cuales se somete el material [12,13]; esto hace que la resistencia aumente y, por lo tanto, la corriente tienda a circular por la periferia del material, provocando que la eficiencia de apantallamiento se vea disminuida. Lo mismo sucede para el aluminio en la figura 3, pero este descenso se presenta cerca a los 20.000 Hz [14].…”

Suppression of Magnetic Signal Error in Trigger Assembly by Simultaneous Sensing of Bipolar Magnets

“…Also, the magnetic shielding had proved experimentally that no virtual trigger signal can be generated by an external magnetic field [3]. However, the shape of the magnetic shielding was restricted by the limited space of small arms and the nature of magnetic sensors that can be operated by a particular magnetic field [4]. Because only partial magnetic shielding can be used for the trigger assembly, it may be impossible to fully shield the magnetic sensor against an external magnetic field in any direction.…”