Technical FAQ

Unlike a Faraday cage, which primarily blocks electric fields and high-frequency electromagnetic waves, low-frequency magnetic shielding does not block the magnetic field like an impermeable barrier.
Its principle involves diverting and channeling the magnetic flux lines by providing them with a preferred path through a material with very high magnetic permeability, such as Mu-metal, Permimphy, or Cryophy. The flux then flows primarily through the shield rather than through the area to be protected.
This is why conventional electrical insulation solutions or high-frequency shielding are generally ineffective against low-frequency magnetic fields, such as those generated by transformers, electric motors, power lines, or railway equipment.

We measure magnetic field attenuation using our Helmholtz coil or Gauss meters. We always provide magnetic field measurements taken on test discs made from the same material batch and subjected to the same heat treatment as the delivered parts.

MECA MAGNETIC has been ISO 9001 certified since 2009. This certification, issued by TÜV and renewed in 2022, confirms that MECA MAGNETIC’s quality system is evaluated annually and found to comply with the manufacturing requirements for our low-frequency magnetic shields.

Composed primarily of nickel and iron, Permimphy is known for its very high magnetic permeability. In environments subject to weak to moderate magnetic fields, it offers excellent attenuation performance and is a proven solution for low-frequency shielding. Historically, it has been used in precision scientific instruments, shielded rooms, and sensitive measuring equipment.

Permimphy has two major limitations that must be taken into account during the design phase :
1. Mechanical sensitivity : Bending, cutting, or welding operations significantly degrade its intrinsic magnetic properties. To achieve theoretical performance, a specific heat treatment (magnetic-grade annealing in hydrogen) must be performed after the part is manufactured.
2. The risk of saturation : When the strength of the stray magnetic field becomes too high, Permimphy reaches its saturation limit and gradually loses its protective effectiveness.

Permimphy offers an excellent balance between high magnetic permeability and good resistance to saturation. It is particularly recommended for industrial and railway environments subject to significant magnetic disturbances. It performs well in demanding low-frequency shielding applications at ambient temperatures.

The magnetic properties of materials change with temperature, and certain alloys optimized for use at room temperature may experience a decline in performance in cryogenic environments. B CryophyB (or Cryoperm) was specifically developed to maintain very high magnetic permeability at low and very low temperatures (on the order of millikelvins). It is therefore a leading solution for cryogenic and quantum applications requiring high attenuation of stray magnetic fields at low temperatures.

Two parts made from the same alloy (whether Permimphy or Cryophy) may exhibit different attenuation factors in the field. The final performance depends not only on the material but also on the part’s geometry, its thickness, the number of layers, the distance from the source, as well as the design of the openings required for cable routing and mechanical assemblies.

There is no single “best” material between Permimphy and Cryophy. The choice depends primarily on the project’s thermal constraints—specifically, the operating temperature of the shielding and the specific magnetic requirements outlined in your specifications. In the low-frequency range, the material is only part of the solution : it is mechanical design expertise and mastery of manufacturing processes that make the difference.

Upon each material receipt and before stocking, we follow defined instructions and procedures:
– the material certificate, which includes a laboratory evaluation of the material’s performance
– the total weight of the shipment
– the dimensions of the sheets
– the thickness of the sheets
– for interior projects, we also conduct a material permeability test on samples taken after heat treatment

Yes, there are European standards on electromagnetic fields. Several European directives and recommendations regulate exposure to electromagnetic fields, with the aim of preventing risks to workers’ health and safety. For example, Directive 2013/35/EU sets exposure limit values and requires preventive measures. In addition, recommendations such as European Union Recommendation 1999/19/EC define thresholds for exposure to electromagnetic fields. These standards are essential for ensuring a safe and healthy work environment.

Each European country may have regulations at the national level that are stricter than these European regulations. This is the case, for example, in France with Decree No. 2013-1162—legifrance.gouv.fr Decree No. 2013-1162 of December 14, 2013—which establishes a stricter framework for certain sensitive environments (hospitals, schools, etc.).

Technical studies show that to optimize a system, it is often more effective to combine several layers of complementary materials rather than seeking a single alloy. A multilayer architecture allows for the division of labor: a first layer absorbs the field’s power to prevent saturation, while a second layer refines the attenuation and controls residual magnetic noise.