There are many risks. We will protect you from all of them.

Every EMF project we undertake has unique challenges. Environmental factors, architectural variables, and equipment specifications are never identical from client to client and all require careful analysis and testing. There’s a lot to understand and no cookie-cutter solutions.

At Vitatech, we make sure you have all the essential information necessary to make informed decisions about your project. And we’re happy to walk you through any and all concerns and questions you may have. Give us a call for a free consultation. 1.540.286.1984

Electromagnetic Fields: An Overview

Whenever electricity (i.e., batteries-DC or electric power-AC) is in use, electric and magnetic fields are produced. If it is alternating current (AC) electric power, the fields fluctuate (expand and collapse) 120 times every second as the 60 cycles-per-second (known as Hertz) alternating current (AC) changes polarity.
Since the AC frequency is 60 Hertz it emanates extremely low frequency (ELF) electromagnetic fields (EMF) – hence the term ELF EMF.

The Sources

Electric fields emanate from unshielded power lines, wires, equipment, and appliances. The electric field strength is measured in volts per meter (V/m). So, under high voltage transmission lines (230 – 500 kV) there are very high electric fields—people can usually hear the crackle and feel the presence on their skin. Fortunately, electric fields can be shielded by grounded objects and materials including metal conduits, trees, and buildings.

Magnetic fields also emanate from unshielded power lines, wires, equipment, and appliances. The magnetic field strength is measured in amperes per meter (A/m) and is proportional to the load current. Therefore, high current loads such as transmission and distribution lines, transformers, feeders, switchgears, and heaters produce high magnetic field levels. Unfortunately, people are not able to sense the presence of high magnetic fields which are extremely difficult to shield—permeating people, buildings, and most metals.

How do you measure it?

Magnetic field exposure is measured as magnetic flux density with a gaussmeter in units of milligauss (mG), which is one-thousandth of a Gauss (G). In scientific terms Gauss (G) is the standard U.S. unit of magnetic flux density—the area permeated by magnetic fields. Therefore, in the United States human exposure to magnetic fields is normally measured and published in milligauss (mG). It should be noted that in Europe microtesla (µT) is the preferred unit – where 1 mG equals 0.1 µT.

Finally, there are both single and triple-axis gaussmeters on the market. A single axis gaussmeter has a magnetic probe (coil, fluxgate or hall-effect) that is sensitive in only one direction: the meter reading is dependent on the orientation of the probe. A triple-axis gaussmeter has three separate magnetic probes placed on the x, y, and z axis. This meter electronically computes the vector sum of the directional components and displays the resultant on a digital readout.

EMF Fundamentals

(excerpted from a published paper by Louis Vitale, Founder & Engineer)

Electric Charge, Current & Voltage

Electric and Magnetic Fields

Magnetic Flux Density & Handy Conversion Factors

ELF EMF, 60-Hz Wavelength, DC & AC Fields

Electrostatic & Electromagnetic Induction

Loop Magnetic Field Sources

Single Conductor Magnetic Field Sources

Dual Conductor Magnetic Field Sources

Three-Phase Magnetic Field Sources

Ground, Plumbing & Net Currents

Video Display Terminals

Magnetic Field Mitigation

Rigid Magnetic Shielding

To Shield or Not to Shield?

Magnetic Shielding Resources

References

Passive or Active? Flux-Entrapment or Lossy Magnetic?
What are the differences?

Passive and Active Mitigation

There are two basic 60-Hz magnetic shielding (reduction) methods: passive and active. Passive magnetic field mitigation includes rigid magnetic shielding with ferromagnetic and highly conductive materials, and the use of passive shield wires installed near transmission lines that generate opposing cancellation fields from electromagnetic induction (beyond the scope of this paper). Active magnetic field mitigation uses electronic feedback to sense a varying 60-Hz magnetic field, then generates a proportionally opposing (nulling) cancellation field within a defined area (room or building) surrounded by cancellation coils. Ideally, when the two opposing 180-degree out-of-phase magnetic fields of equal magnitude intersect, the resultant magnetic field is completely canceled (nullified). This technology has been successfully applied in both residential and commercial environments to mitigate magnetic fields from overhead transmission and distribution lines, and underground residential distribution (URD) lines.

Flux-Entrapment Shields

A flux-entrapment shield is constructed with ferromagnetic, highly permeable (µ-mu), 80% nickel-20% iron alloy (i.e., Hipernom Alloy, CO-NETIC AA, Aumetal, AD-MU-80, etc.) which either surrounds (cylinder or rectangular box) or separates (“U” shaped or flat-plate) the area from the magnetic source. Ideally, magnetic flux lines incident upon the flux entrapment shield prefers to enter the highly permeable (µ-mu) material, traveling inside the material via the path of least magnetic reluctance (R), rather than passing into the protected (shielded) space.

Lossy Magnetic Shields

Lossy magnetic shielding depends on the eddy-current losses that occur within highly conductive materials (i.e., copper, aluminum, iron, steel, silicon-iron, etc.). When a conductive material is subjected to a time-varying (60 hertz) magnetic field, currents are induced within the material that flow in closed circular paths – perpendicular to the inducing field. According to Lenz’s Law, these eddy-currents oppose the changes in the inducing field, so the magnetic fields produced by the circulating eddy- currents attempt to cancel the larger external inducing magnetic fields near the conductive surface, thereby generating a shielding effect.

Shielding Factor
Exposure Risks
To Shield or Not to Shield
Are You a Design Engineer?

Whatever your tool, we protect it

VITATECH protects the following list of equipment and many other sensitive tools:

  • Scanning Electron Microscope (SEM)
  • Transmission Electron Microscope (TEM)
  • Scanning Transmission Electron Microscope (STEM)
  • Atomic Force Microscope (AFM)
  • Focused Ion Beam (FIB)
  • Electron Beam (E-BEAM)
  • Nuclear Magnetic Resonance (NMR)
  • Electron Magnetic Resonance (EMR)
  • Magnetic Resonance Imaging (MRI)
  • Computed Axial Tomography (CAT)
  • Electroencephalography (EEG)
  • Electrocardiography (EKG)
  • Electromyography (EMG)
  • Positron Emission Tomography (PET)
  • Magnetoencephalography (MEG)