Electromagnetic shielding:
Electromagnetic shielding is the practice of reducing the "electromagnetic field" in a space by blocking the field with barriers made of conductive or magnetic materials. Shielding is typically applied to enclosures to isolate electrical devices from the 'outside world', and to cables to isolate wires from the environment through which the cable runs. Electromagnetic shielding that blocks "radio frequency electromagnetic radiation" is also known as RF shielding.
The shielding can reduce the coupling of "radio waves, electromagnetic fields and electrostatic fields". A conductive enclosure used to block electrostatic fields is also known as a "Faraday cage". The amount of reduction depends very much upon the material used, its thickness, the size of the shielded volume and the frequency of the fields of interest and the size, shape and orientation of apertures in a shield to an incident electromagnetic field.
Electromagnetic shielding is the practice of reducing the "electromagnetic field" in a space by blocking the field with barriers made of conductive or magnetic materials. Shielding is typically applied to enclosures to isolate electrical devices from the 'outside world', and to cables to isolate wires from the environment through which the cable runs. Electromagnetic shielding that blocks "radio frequency electromagnetic radiation" is also known as RF shielding.
The shielding can reduce the coupling of "radio waves, electromagnetic fields and electrostatic fields". A conductive enclosure used to block electrostatic fields is also known as a "Faraday cage". The amount of reduction depends very much upon the material used, its thickness, the size of the shielded volume and the frequency of the fields of interest and the size, shape and orientation of apertures in a shield to an incident electromagnetic field.
Electromagnetic radiation shielding products:
• Meters..
• Bed canopies.
• Shielding fabrics
• Shielding films.
• Shielding paints & covers.
• “Dirty Electricity” Meter and Filters.
• Cell Phone Warning Signage.
• Low Radiation Mobile Headset / Mobile cases.
• Grounding Devices.
• Computer accessories.
• Smart meters.
• Faraday cage.
• Anechoic chamber.
• Meters..
• Bed canopies.
• Shielding fabrics
• Shielding films.
• Shielding paints & covers.
• “Dirty Electricity” Meter and Filters.
• Cell Phone Warning Signage.
• Low Radiation Mobile Headset / Mobile cases.
• Grounding Devices.
• Computer accessories.
• Smart meters.
• Faraday cage.
• Anechoic chamber.
EMR Meters:
RF Spectrum analyzer:
|
|
Acoustimeter:
Microtesla meter:
Bed canopies:
|
|
Shielding fabrics:
|
|
Shielding films:
Shielding Paints and Covers:
|
|
Reducing Cell Phone Headsets, Cell Phone Cases:
|
|
|
|
CRUZ CASE for iPhone 6:
|
|
|
|
|
|
Grounding Devices:
|
|
|
|
|
|
Faraday cage:
Faraday shield is an enclosure formed by conductive material or by a mesh of such material, used to block electric fields. Faraday cages are named after the English scientist Michael Faraday, who invented them in 1836.
A Faraday cage operates because an external electrical field causes the electric charges within the cage's conducting material to be distributed such that they cancel the field's effect in the cage's interior. This phenomenon is used to protect sensitive electronic equipment from external radio frequency interference (RFI). Faraday cages are also used to enclose devices that produce RFI, such as radio transmitters, to prevent their radio waves from interfering with other nearby equipment. They are also used to protect people and equipment against actual electric currents such as lightning strikes and electrostatic discharges, since the enclosing cage conducts current around the outside of the enclosed space and none passes though the interior.
Faraday shield is an enclosure formed by conductive material or by a mesh of such material, used to block electric fields. Faraday cages are named after the English scientist Michael Faraday, who invented them in 1836.
A Faraday cage operates because an external electrical field causes the electric charges within the cage's conducting material to be distributed such that they cancel the field's effect in the cage's interior. This phenomenon is used to protect sensitive electronic equipment from external radio frequency interference (RFI). Faraday cages are also used to enclose devices that produce RFI, such as radio transmitters, to prevent their radio waves from interfering with other nearby equipment. They are also used to protect people and equipment against actual electric currents such as lightning strikes and electrostatic discharges, since the enclosing cage conducts current around the outside of the enclosed space and none passes though the interior.
|
|
|
|
Anechoic chamber:
|
|
Materials used:
Typical materials used for electromagnetic shielding include "sheet metal, metal screen, and metal foam". Any holes in the shield or mesh must be significantly smaller than the "wavelength" of the radiation that is being kept out, or the enclosure will not effectively approximate an unbroken conducting surface.
Another commonly used shielding method, especially with electronic goods housed in plastic enclosures, is to coat the inside of the enclosure with a metallic ink or similar material. The ink consists of a carrier material loaded with a suitable metal, typically "copper or nickel", in the form of very small particulates. It is sprayed on to the enclosure and, once dry, produces a continuous conductive layer of metal, which can be electrically connected to the chassis ground of the equipment, thus providing effective shielding.
RF shielding enclosures filter a range of frequencies for specific conditions. "Copper is used for radio frequency (RF) shielding because it absorbs radio and magnetic waves". Properly designed and constructed "copper RF shielding enclosures satisfy most RF shielding needs, from computer and electrical switching rooms to hospital CAT-scan and MRI facilities".
Typical materials used for electromagnetic shielding include "sheet metal, metal screen, and metal foam". Any holes in the shield or mesh must be significantly smaller than the "wavelength" of the radiation that is being kept out, or the enclosure will not effectively approximate an unbroken conducting surface.
Another commonly used shielding method, especially with electronic goods housed in plastic enclosures, is to coat the inside of the enclosure with a metallic ink or similar material. The ink consists of a carrier material loaded with a suitable metal, typically "copper or nickel", in the form of very small particulates. It is sprayed on to the enclosure and, once dry, produces a continuous conductive layer of metal, which can be electrically connected to the chassis ground of the equipment, thus providing effective shielding.
RF shielding enclosures filter a range of frequencies for specific conditions. "Copper is used for radio frequency (RF) shielding because it absorbs radio and magnetic waves". Properly designed and constructed "copper RF shielding enclosures satisfy most RF shielding needs, from computer and electrical switching rooms to hospital CAT-scan and MRI facilities".
Example applications:
Electromagnetic radiation consists of coupled "electric and magnetic fields". The electric field produces "forces" on the "charge" carriers (i.e., electrons) within the conductor. As soon as an electric field is applied to the surface of an ideal conductor, it induces a "current" that causes displacement of charge inside the conductor that cancels the applied field inside, at which point the current stops.
Similarly, varying "magnetic fields" generate "eddy currents" that act to cancel the applied magnetic field. (The conductor does not respond to static magnetic fields unless the conductor is moving relative to the magnetic field.) The result is that "electromagnetic radiation" is reflected from the surface of the conductor: internal fields stay inside, and external fields stay outside.
Several factors serve to limit the shielding capability of real RF shields. One is that, due to the "electrical resistance" of the conductor, the excited field does not completely cancel the incident field. Also, most conductors exhibit a "ferromagnetic" response to low-frequency magnetic fields, so that such fields are not fully attenuated by the conductor. Any holes in the shield force current to flow around them, so that fields passing through the holes do not excite opposing electromagnetic fields. These effects reduce the field-reflecting capability of the shield.
In the case of "high-frequency electromagnetic radiation", the above-mentioned adjustments take a non-negligible amount of time, yet any such radiation energy, as far as it is not reflected, is absorbed by the skin (unless it is extremely thin), so in this case there is no electromagnetic field inside either. This is one aspect of a greater phenomenon called the "skin effect". A measure of the depth to which radiation can penetrate the shield is the so-called "skin depth".
Electromagnetic radiation consists of coupled "electric and magnetic fields". The electric field produces "forces" on the "charge" carriers (i.e., electrons) within the conductor. As soon as an electric field is applied to the surface of an ideal conductor, it induces a "current" that causes displacement of charge inside the conductor that cancels the applied field inside, at which point the current stops.
Similarly, varying "magnetic fields" generate "eddy currents" that act to cancel the applied magnetic field. (The conductor does not respond to static magnetic fields unless the conductor is moving relative to the magnetic field.) The result is that "electromagnetic radiation" is reflected from the surface of the conductor: internal fields stay inside, and external fields stay outside.
Several factors serve to limit the shielding capability of real RF shields. One is that, due to the "electrical resistance" of the conductor, the excited field does not completely cancel the incident field. Also, most conductors exhibit a "ferromagnetic" response to low-frequency magnetic fields, so that such fields are not fully attenuated by the conductor. Any holes in the shield force current to flow around them, so that fields passing through the holes do not excite opposing electromagnetic fields. These effects reduce the field-reflecting capability of the shield.
In the case of "high-frequency electromagnetic radiation", the above-mentioned adjustments take a non-negligible amount of time, yet any such radiation energy, as far as it is not reflected, is absorbed by the skin (unless it is extremely thin), so in this case there is no electromagnetic field inside either. This is one aspect of a greater phenomenon called the "skin effect". A measure of the depth to which radiation can penetrate the shield is the so-called "skin depth".
How electromagnetic shielding works:
Electromagnetic radiation consists of coupled "electric and magnetic fields". The electric field produces "forces on the charge carriers"
(i.e., electrons) within the conductor. As soon as an electric field is applied to the surface of an ideal conductor, it induces a current that causes displacement of charge inside the conductor that cancels the applied field inside, at which point the current stops.
Similarly, varying "magnetic fields generate eddy currents" that act to cancel the applied magnetic field. (The conductor does not respond to static magnetic fields unless the conductor is moving relative to the magnetic field.) The result is that "electromagnetic radiation" is reflected from the surface of the conductor: internal fields stay inside, and external fields stay outside.
Several factors serve to limit the shielding capability of real RF shields. One is that, due to the "electrical resistance" of the conductor, the excited field does not completely cancel the incident field. Also, most conductors exhibit a "ferromagnetic" response to low-frequency magnetic fields, so that such fields are not fully attenuated by the conductor. Any holes in the shield force current to flow around them, so that fields passing through the holes do not excite opposing electromagnetic fields. These effects reduce the field-reflecting capability of the shield.
In the case of high-frequency electromagnetic radiation, the above-mentioned adjustments take a non-negligible amount of time, yet any such radiation energy, as far as it is not reflected, is absorbed by the skin (unless it is extremely thin), so in this case there is no electromagnetic field inside either. This is one aspect of a greater phenomenon called the "skin effect". A measure of the depth to which radiation can penetrate the shield is the so-called "skin depth".
Electromagnetic radiation consists of coupled "electric and magnetic fields". The electric field produces "forces on the charge carriers"
(i.e., electrons) within the conductor. As soon as an electric field is applied to the surface of an ideal conductor, it induces a current that causes displacement of charge inside the conductor that cancels the applied field inside, at which point the current stops.
Similarly, varying "magnetic fields generate eddy currents" that act to cancel the applied magnetic field. (The conductor does not respond to static magnetic fields unless the conductor is moving relative to the magnetic field.) The result is that "electromagnetic radiation" is reflected from the surface of the conductor: internal fields stay inside, and external fields stay outside.
Several factors serve to limit the shielding capability of real RF shields. One is that, due to the "electrical resistance" of the conductor, the excited field does not completely cancel the incident field. Also, most conductors exhibit a "ferromagnetic" response to low-frequency magnetic fields, so that such fields are not fully attenuated by the conductor. Any holes in the shield force current to flow around them, so that fields passing through the holes do not excite opposing electromagnetic fields. These effects reduce the field-reflecting capability of the shield.
In the case of high-frequency electromagnetic radiation, the above-mentioned adjustments take a non-negligible amount of time, yet any such radiation energy, as far as it is not reflected, is absorbed by the skin (unless it is extremely thin), so in this case there is no electromagnetic field inside either. This is one aspect of a greater phenomenon called the "skin effect". A measure of the depth to which radiation can penetrate the shield is the so-called "skin depth".
Magnetic shielding:
Equipment sometimes requires isolation from external magnetic fields. For static or slowly varying magnetic fields (below about 100 kHz) the Faraday shielding described above is ineffective. In these cases shields made of high "magnetic permeability metal alloys" can be used, such as sheets of "Permalloy and Mu-Metal", or with nano crystalline grain structure ferromagnetic metal coatings. These materials don't block the magnetic field, as with electric shielding, but rather draw the field into themselves, providing a path for the "magnetic field lines" around the shielded volume. The best shape for magnetic shields is thus a closed container surrounding the shielded volume. The effectiveness of this type of shielding depends on the material's permeability, which generally drops off at both very low magnetic field strengths and at high field strengths where the material becomes "saturated". So to achieve low residual fields, magnetic shields often consist of several enclosures one inside the other, each of which successively reduces the field inside it.
Because of the above limitations of passive shielding, an alternative used with static or low-frequency fields is active shielding; using a field created by "electromagnets" to cancel the ambient field within a volume."Solenoids and Helmholtz coils" are types of coils that can be used for this purpose.
Additionally, "superconducting materials" can expel magnetic fields via the Meissner effect.
Equipment sometimes requires isolation from external magnetic fields. For static or slowly varying magnetic fields (below about 100 kHz) the Faraday shielding described above is ineffective. In these cases shields made of high "magnetic permeability metal alloys" can be used, such as sheets of "Permalloy and Mu-Metal", or with nano crystalline grain structure ferromagnetic metal coatings. These materials don't block the magnetic field, as with electric shielding, but rather draw the field into themselves, providing a path for the "magnetic field lines" around the shielded volume. The best shape for magnetic shields is thus a closed container surrounding the shielded volume. The effectiveness of this type of shielding depends on the material's permeability, which generally drops off at both very low magnetic field strengths and at high field strengths where the material becomes "saturated". So to achieve low residual fields, magnetic shields often consist of several enclosures one inside the other, each of which successively reduces the field inside it.
Because of the above limitations of passive shielding, an alternative used with static or low-frequency fields is active shielding; using a field created by "electromagnets" to cancel the ambient field within a volume."Solenoids and Helmholtz coils" are types of coils that can be used for this purpose.
Additionally, "superconducting materials" can expel magnetic fields via the Meissner effect.