Shielding Effectiveness (SE)
Given the sensitivity of human living organisms to subtle electromagnetic fields (EMFs), a number of shielding techniques have been developed to counter or alleviate their impact on health.
When shielding material is placed or applied between the source of radiation and the point of measurement, shielding effectiveness is characterized by i) frequency, ii) reflection, iii) absorption & iv) transmission whose characteristics are defined by the following parameters:
- Geometric characteristics: thickness and distance vs wavelength,
- Physical properties: the ability to transmit or permit electric field (electrical conductivity) & to support the formation of a magnetic field within itself in response to an applied magnetic field (permeability). Material absorption increases with thickness, permeability, conductivity, and frequency. That is why shielding effectiveness increases with frequency,
- Properties of incident radiation: Electric field intensity E in V/m, magnetic field intensity B in µT or nT, magneticfield H in A/m, radio frequency radiation density µW/m², frequency f, and angle of incidence θ.
Let us assume:
I= Incident radiation R= Primary reflection B= secondary reflection A= absorption T= transmission
Transmission T = I-R-B-A this leads to :
Radio frequency shielding effectiveness in -dB = 10 log T/I
Electric field shielding effectiveness in -dB = 20 log Ea/Eb
Magnetic field shielding effectiveness in -dB = 20 log Ba/Bb a=after & b=before
Shielding effectiveness …examples 1) Austria —referencr Yshield catalog...
Fig 1)—————————— Fig 2) ———————- Fig 3)
Fig 1) Painting in process Fig 2) Exterior painted Fig 3) Back to its original color
Shielding a family house from 194 µW/m² to 0.01 µW/m² Austria (using HSF 54 paint)
Results: Shielding effectiveness as reported -42 dB, in percentage: 99.994%
Shielding effectiveness …examples 2) New Zealand
Shielding one corner of a study room against Smart Meter’s RF signal burst at 650 µW/m² down to 0.4 µW/m² using aluminum foil.
Results: Shielding effectiveness -32 dB, in percentage: 99.938%
Please take note that choosing the right shielding material/fabric requires correct interpretation of measurements, evaluation, and proper remediation. It is not a trial and error. It is to do with the most precious asset “Human Health”. If deemed necessary, we take the shielding effectiveness to new levels, follow through with health improvement of our customers.
As you may have noticed from reading through the pages, shielding could be a long interactive process with the client. Every case is different.
For more information/comments, don’t hesitate to contact us. Drop us a line at email@example.com Auckland 2016, New Zealand.
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