electromagnetic radiations protection

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2. Radiation : The process by which unstable nuclei of
atom emit a quantity of energy, or a particle. This emitted
particle or energy is known as radiation.
Classification of radiations:
1. Particle radiation (tiny and fast moving material having
both energy and weight)
2. Electro magnetic radiation (pure energy )
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3. Electromagnetic radiation (EM radiation or EMR) is a form of energy
emitted by charged particles, which exhibits wave-like behavior as it
travels through space.
EMR has both electric and magnetic field components, which stand
in a fixed ratio of intensity to each other, and which oscillate in phase
perpendicular to each other and perpendicular to the direction of
energy and wave propagation.
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5. 1. Electromagnetic waves are propagated by oscillating electric
and magnetic fields oscillating at right angles to each other.
2. Electromagnetic waves travel with a constant velocity of 3 x
108 ms-1 in vacuum.
3. Electromagnetic waves are not deflected by electric or
magnetic field
4. Electromagnetic waves can show interference or diffraction.
5. Electromagnetic waves are transverse waves.
6. Electromagnetic waves may be polarized.
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6. Natural sources Man made sources
cosmic exposure at public places
terrestrial occupational exposure
internal
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7. Broadcast antennas Cell towers
Digital TV signals Doppler weather radar
Electric trains Over telephone wires
Microwave beacons Pagers
Power lines Radio transmitters
Satellite radiation Wi-Fi antennas
Wiring in airplanes Digital display
Cell phone chargers Cell phones
Compact fluorescent light (CFL) Computers
Cordless phones
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10. Electrical hazards : Strong radiation can induced current capable
of delivering an electric shock to persons and animals. It can also
overload and destroy electrical equipment.
Fire hazards : EMR can cause electric currents strong enough to
create sparks and can ignite flammable material and gases , leading
to an explosion.
Biological hazards : EM field can cause dielectric heating ex.
Touching and antenna can cause severe burns.
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11. EMR can cause cancer , high blood pressure , brain tumors ,
headache, leukemia, brain damage etc.
WHO facts says that EMR can cause depression , cardiovascular
disorder, reproductive function, developmental disorders,
immunological modification etc. but these have lesser chances
than for child hood leukemia.
Electromagnetic interference : it is an unwanted disturbance
that effect the electrical circuit due to EMR emitted from an
external source .
It May interrupt , obstruct or limit the effective performance of
the circuit.
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12. Energy of the incident radiation
Depth of penetration
Source of emission
Duration of exposure
Frequency of EMR waves
Type of EMR waves
Distance from the object
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13. It is a process by which a material is able to reduce the
transmission of EMR that effects the humans or equipments.
EMS material are used to exclude the unwanted EMR or signals. It
also provide protection against the EM pulses which can disrupt
neighbouring computers .
It provides protection by reducing signals to level at which they no
longer effect equipment or can no longer be received. This is
achieved by reflecting and absorbing the radiation.
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14. The primary mechanism of EMI shielding is usually reflection.
For reflection of the radiation by the shield, the shield must have
mobile charge carriers (electrons or holes) which interact with the
electromagnetic fields in the radiation.
A secondary mechanism of EMI shielding is usually absorption. For
significant absorption of the radiation by the shield, the shield
should have electric and/or magnetic dipoles which interact with the
electromagnetic fields in the radiation.
Other than reflection and absorption, a mechanism of shielding is
multiple reflections, which refer to the reflections at various surfaces
or interfaces in the shield.
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15. How EMS Works
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16. Electromagnetic shielding is used in,
Aerospace aviation: In protection of highly advanced avionic
equipments.
Anti-terrorism: Encryption of relevant secret codes related to
national security.
Communication: Safeguarding highly sensitive digital signal
processing and microwave operating band
Defense: To protect equipment related to military, navy or air force.
Information Technology: Protect users from radioactive effects of
computers and peripherals.
Medical: Prevents interference of electromagnetic waves given out
by medical devices especially during critical operations.
Transport: For improved performances of automomotive
electronics luxury devices, vehicle tracking system and detection
surveillance systems, electric cars etc. 16

17. 1. Conductive materials
2. Nano and micro-carbon black
3. Sub micro- and micro-powders of Al, Cu, Ni etc.
4. Stainless steel fibers
5. Silver-coated polyamide fibres
6. Plastic fibre such as poly phenylene vinylene , poly
Acetylene(doped form)
7. Cellulosic fibers.
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18. Reflection /absorption / multi reflection of EM waves
It should be flexible & light weight.
Conductivity
Corrosion resistant
Durability
Low cost etc.
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19. Material used for EMS include sheet metal mesh , metal form ,And
plasma .
Multi layer knitted fabric such as interlock structure
Textile Multi layer structure
Composite materials for shielding
Conductive fabric
Shielding foil tapes
EMI conductive adhesives
Mostly conductive fabric are used prepared with different
techniques.
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20. Incorporation of conductive fibres or yarns in to the fabric
Lamination of conductive layer on to the surface of the fabric such
as conductive coating , spray ,ionic plating .
Addition to the conductive fillers such as conductive carbon black,
carbon fibre ,metal fibre (stainless steal AL, CU),metal powder and
flex to the insulating material
Grafting a conductive polymer such as poly anilines , poly pyrolle
, poly vinyl alchol,poly amide on to the fabric
Coating of individual fibre by conductive polymer
Few examples : Filosano fabric , Flectron , Phantom fabric, High
performance silver mesh fabric etc.
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21. Shielding effectiveness:- It is the ratio of electromagnetic field
strength measured without (E0) & with (E1) the tested material
when it separates the field source and the receptor. It I s given by
SE = Eo /E1
Insertion loss (A) : It is a measure of losses in a transmission
signal cause by the tested material being inserted in to the
measuring channel . It is given by
A = Uo/ U1
Where Uo = channel out put voltage without tested material
U1 = output voltage with tested material
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22. For woven fabric :
1. Effect of type of material: metals have significantly higher
EMS value compare to polymer or cellulosic material
Metal > cellulose > polyester (synthetic polymer)
2. Effect of no. of apertures : EMS value decreases with
increase in no. of holes . However for metals no significance
difference is there in shielding.
3. Effect of yarn count and thread density : with increase in
yarn count the effectiveness increases.
4. Effect of no. of fabric layers : the shielding of the material is
directly proportional to the thickness of the material.
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23. 1. Effect of metal wire diameter: With increase in dia. the
shielding effectiveness decreases .
2. Effect of knitted structure : Interlock and rib structure have
more shielding effectiveness then the plain structure.
3. Effect of thickness: Thickness of the knitted fabric shows
negligible influence on EMS effectiveness at low to higher
frequency.
4. Effect of tightness factor : Fabric with higher tightness factor
have good shielding effectiveness then lower.
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24. Mil –STD 285 :
1. Introduced in 1956
2. This standard has an upper frequency limit of 400 MHz
3. Developed for large-enclosure and shelter assessment.
IEEE-STD 299:
1. Developed by institute of electrical and electronics engg.
2. Upper freq. limit 100 GHz.
3. This standard is only applicable to an enclosure whose
smallest linear dimension is > 2mt.
4. It does not apply on small and medium size enclosure .
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27. ASTM-E1851 :
1. Developed by the American society for testing and materials .
2. It requires freq. range between 140 and 160 KHz and between 14
to 16 MHz.
3. Far field shielding measurement between 300 to 500 MHz, 900
to 1000 MHz , and 8.5 and 10.5 GHz are required .
4. Used for large enclosure and shelters.
VG 95373 part 15 :
1. German military standard.
2. The freq. range above 30 to 200 MHz
3. Minimum antenna to enclosure separation distance of 2.5 mt.
4. Only standard applicable to small and medium sized enclosures.
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28. ASTM-D 4935 :
1. Developed for evaluation of flat thin samples .
2. This standard is used for plastic materials .
3. Freq. range from 30 MHz to 100 MHz.
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29. The EMR are increasing day by day due the increasing use of
electronics equipment and other sources of EMR . Since the EMR are
harmful for us, so it’s a big issue of concern. Due to the new
technologies and advancement such as use of conductive polymer
,multi layer fabrics and composites etc. the EMR hazards can be reduce
to some extent. After considering the different parameters of
construction for EMS , the effectiveness can be increased . In recent
year conductive fabric considered mainly due to their characteristics of
flexibility , lightness and competitive price.
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30. 1. R Perumalraj, B.S. Dasaradan and are Nagaswarana, Electrically
conductive polymer materials for EMI Shielding, Asian Textile Journal,
Jan. 2009 (p- 49 to 57).
2. R Perumalraj, B.S. Dasaradan, Electromagnetic shielding fabric, Asian
Textile Journal , Oct. 2008 (p-62to 68).
3. R Perumalraj , B.S. Dasaradan , Electromagnetic shielding effectiveness
of copper core yarn knitted fabric , Indian Journal of Fibre and Textile
Research, vol-34 , June 2009 (p-149-154).
4. A.Das, V.K. Kothari, A. Kothari and A.Kumar, effect of various
parameter on EMS effectiveness of textile fabric , Indian Journal of
Fibre and Textile Research, vol-34 , June 2009 (p-144-148).
5. K.K.Gupta , S.M. Abbas and A.Srivastava, Microwave interactive fabric:
A review , Man Made Textiles in India , Feb 2012 (p-41t0 48).
6. P.R.Surwase, EMI shielding Material and measuring methods : A
Review , Man Made Textiles in India , Sep. 2011 (p-327 to 330).
7. Department of defense, United States of America,MIL – STD 285 .
8. V.K. Kothari ,Progress in Textile Science & Technology, vol. 3, (p-396).
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