Coming soon……….When and where mumetal ® is commonly used
Whilst mu metal ® is available in many different gauges and indeed a single layer is suitable for most commercial applications, optimal shielding results are obtained when a shield is constructed of multiple layers of mu metal ®.
In theory each layer should be of a light gauge and the shield constructed of many layers (T. Rikitake – Magnetic and Electromagnetic Shielding 1987) in practice this not always possible from a mechanical point of view and it will be necessary to reach a compromise between number of layers for best shielding factor and structural requirements.
Evidence has shown that a multi layer shield of 4 layers has greatly improved shielding characteristics than one single layer of the same internal and external radii (example: 1 x layer of 10mm as opposed to 4 x layers of 1mm with 3 x 2mm air-gap) Adopting this method not only increases the shielding factor, it also Read the rest of Multiple Layer Shields »
What is field attenuation?
This is also known as the shielding factor (S) and is a ratio of the magnetic field strength outside of the magnetic shield (Ha) and the resultant field on the inside of the shield ie Ha/Hi (no units) or S = 20 x log(Ha/Hi) (Db). There are various formula based on the permeability of the material, the shape and size of the shield and the material thickness. In most cases these formulae are only approximate.
For a closed shielding can :
S = 4/3 X (Mu x d/D) where Mu : The permeability(relative)
d : material thickness Read the rest of Shielding calculation formula »
Tags: density, foil, magnetic fields, magnetic shield, magnetic shielding, magnetic shields, mu metal, mumetal, mumetal specifications, nickel-iron alloy, permeability, sheet, wire Posted in Shielding Information by
Admin.
Mumetal ® is one of a family of three Nickel-Iron alloys widely used to produce magnetic parts and shielding.
The three alloys concerned have the following approximate compositions and well known trade names:-
36%NiFe widely known as Supra 36, Nilomag36, Radiometal 36, Magnifer36
50%NiFe widely known as Supra 50, Nilomag 50, Radiometal 50, Magnifer 50
80%NiFe 5%Mo widely known as Mumetal ®, Magnifer
For shielding applications it is possible to use a combination Read the rest of Mumetal is one of a family of three Nickel-Iron alloys »
Mu Metal ® Mechanical properties at ambient temperature (reference guide)
Density: 8.7 [g/cm^3]
Youngs Modulus: 225 [GPa]
Poissons Ratio: 0.29 Read the rest of Mu Metal mechanical properties »
Specifications : ASTM A-753 Alloy 4, MIL N-14411C Composition. Mu metal is a 80 % Nickel, 4.5 % Molybdenum, balance Iron soft ferromagnetic alloy which means that it does not retain a field after the removal of an external magnetizing force. Mu-metal ® offers exceptionally high initial and maximum permeability with minimum hysteresis loss. It also has very low coercive force, very low core losses and a low remanence. To reach the required magnetic performance mumetal needs to undergo a full final Read the rest of Mu metal specifications »
The most efficient magnetic shield shape is a spherical shield but this is difficult to manufacture in production terms. The next best is a cylinder with closed ends. The rounded surface of the cylinder is conductive to the absorption of magnetic flux. If the cylinder does not have end caps, the ratio of the length to the diameter should be 4:1.
If space is at a premium, as well as being more practical for mechanical reasons then a flat sided box Read the rest of What is the best shield shape? »
Most people are familiar with what a Magnetic Shield does, it simply stops or negates unwanted interference from magnetic fields. Not so many people are familiar with how it actually does it.
There are various types of ways and materials used in Magnetic Shielding depending on the frequency and strengths of the magnetic field.
Read the rest of How does a Magnetic Shield work? »
Most people are familiar with what a Magnetic Shield does, it simply stops or negates unwanted interference from magnetic fields. Not so many people are familiar with how it actually does it.