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Measuring Magnetic Fields
How do you "see" magnetic fields? By using a Gauss Meter, the electromagnetic source field strength is measured in "Gauss", and output into numeric values. An example of measuring gauss before and after shielding an electrical panel with our MuMETAL® alloy can be seen on YouTube. We offer a cost effective, handheld, single-axis AC magnetic field meter, to provide quick & reliable measurements of electromagnetic field (EMF) radiation generated by external sources like power lines, electrical wiring, audio/visual equipment, motors and other devices. No probe is required - just hold the Gaussmeter in the affected area. Then measure the same after shielding with MuMETAL®, Co-NETIC®, NETIC®, or CRYO-NETIC® shielding alloys. To experiment and test "hands-on" with one of our evaluation kits, one including a Gaussmeter, specially priced with a 10% savings, get detailed specifications and order here: Evaluation Kits.
How do you calculate shielding requirements? At the bottom of this page are our Slide Rule Calculator, Online Calculator, and B-H Curve. These valuable tools can help you compare our shielding alloys, different thicknesses, and shielding efficiencies, and select the size of shielding required to reduce (attenuate) unwanted fields. But first, we want to familiarize you with our specialty alloys and explain their differences.
Shielding efficiency is a result of material composition, specific gravity, thickness, grain structure within the alloy, and hardness. Depending on strength of the unwanted field (HO) and the amount of field Attenuation you need, one of our four alloy types may be selected.
Our most popular shielding alloy - so popular the name has been used generically in worldwide markets. Buyers beware: MuMETAL® is a registered brand of Magnetic Shield Corporation, and we do not support other companies that sell shielding materials they claim are mumetal. MuMETAL® is not a generic name - it is a proprietary brand that we certify to exacting quality standards and material specifications. MuMETAL® offers maximum permeability µ (Mu) and is used primarily in low intensity fields where high attenuation, high initial permeability and high shielding efficiency are desired. Available as stress annealed (partially annealed for ease of machinability), sheet stock is used for fabricated shields such as enclosures, cylinders, cans, channels or 3D boxes. Typically, atmospherically controlled annealing is required after stamping, machining, bending, rolling or welding to provide maximum shielding performance. MuMETAL® is available in many forms, but most shields are fabricated from our MuMETAL® Sheet and Foil. Our sheet supply is stocked in gauges from 0.014" to 0.080" thickness [0,36mm to 2,00mm], and foil in gauges from .002" to .010" thickness [0,05mm to 0,25mm].
MuMETAL® Stress Annealed plate is used primarily in low intensity fields where high attenuation is desired (high initial permeability & high shielding efficiency). Available as stress annealed; partially annealed for ease of machinability. Our plate supply is stocked with the thickest select gauges from 0.098" to 0.197" thickness [2,5mm to 5,0mm].
Ready to use from stock, Co-NETIC® AA Perfection Annealed alloy is used for flat shields such as covers, doors, walls and simple two-dimensional shapes. Considered far superior to other alloys because of our Perfection Annealing process, it is used where maximum attenuation is desired. Co-NETIC® is fully annealed to exacting specifications in a quality controlled environment which builds grain structure, an important mechanical property for ultimate shielding performance. Co-NETIC® AA Perfection Annealed alloy is available in foil & sheet stock gauges from .002" to .062" thickness [0,05mm to 1,57mm].
Co-NETIC® B Stress Annealed Plate is a sheet form offered in thicker gauges. This alloy has a slightly different formulation than our Co-NETIC® AA with attenuation characteristics set between Co-NETIC® AA and NETIC® S3-6. It is useful in certain applications where the very high attenuation of Co-NETIC® AA is not required. Co-NETIC® B is useful when medium permeability is needed. Available in select stock gauges from 0.020" [0,50mm] to 0.098" [2,50mm]. Other gauges available by request.
Often applied in fields of high intensity (strong fields), NETIC® provides high magnetic saturation characteristics. It has the ability to absorb stronger electro-magnetic fields without saturating. In complex fields, NETIC® is commonly used in combination (in layers) with Co-NETIC® or MuMETAL®, with the NETIC® layer placed closest to the source of interference. Used for either fabricated or flat shields, it may be re-annealed for better performance. NETIC® Sheet and Foil are available in stock gauges from .004" to .095" thickness [0,10mm to 2,41mm].
Foil Types Available:
NETIC® S3-6 is Uncoated
NETIC® S3-6 with Pressure Sensitive Tape (PST)
NETIC® S3-6 Electro-Tin Plated (For electronics applications requiring corrosion resistance)
CRYO-NETIC® Sheet is our proprietary nickel-iron soft magnetic alloy that is ideal for shielding unwanted magnetic fields at extremely low temperatures, typically 77 Kelvin (liquid nitrogen) and 4 Kelvin (liquid helium). Many high energy physics research applications are conducted under cryogenic temperatures, but still require shielding. The permeability of our MuMETAL® and Co-NETIC® alloys begin to decline at -40 degrees, which is why we offer our CRYO-NETIC® magnetic shielding alloy for increasing permeability with decreasing temperature. These Stress Annealed Sheets are of soft temper for ease of fabricating shields such as enclosures, cylinders, cans, channels or 3D boxes. Stress Annealed Sheet is stocked in gauges 0.040" and 0.059" thickness [1,0mm to 1,50mm].
After fabricating a magnetic shield, final annealing is generally required to increase grain structure, which improves shielding efficiency. Final anneal is a critical process step and extra care must be taken to avoid dropping or denting as shock may weaken an annealed shield's grain structure. When MuMETAL® magnetic shields are provided they are Perfection Annealed (fully annealed in a controlled hydrogen atmosphere) to Magnetic Shield Corporation's exacting standards. Optimum magnetic properties are obtained by annealing at a temperature of 1950-2050°F [about 1120°C], and cooling at a consistent rate which is critical to maintaining grain structure and part dimensions.
Quality Control Lab Advantage
Fabrication to spec and parts production quality including the final Perfection Annealing process determines the overall shielding attenuation required for critical applications performance. Magnetic Shield Corp. has processes and procedures established as an ISO 9001:2015 certified company to verify manufacturing quality standards at our in-house Quality Control Lab facility. Stock and custom shields go through our QC Lab for inspection, testing, and measurement of attenuation (a shield's ability to absorb magnetic energy) using Helmholtz Coils. Fully annealed MuMETAL® offers attenuation properties that are considered the best available for most low field applications worldwide.
We are committed to excellence in providing our product solutions, alloy materials, fabrication, finishes, services, heat treatment annealing, and very importantly, taking great care with packing materials to protect your shielding investment.
Formulas may be used to determine which materials and thicknesses will provide the most effective shielding. The source (interfering) field known as HO is measured in Gauss. Knowing HO, and estimating the approximate size of your shield, shield thickness can be determined. Certain characteristics of shielding alloys are theoretically constant such as permeability µ (Mu), saturation induction, and flux density (B).
Usually, theory provides no finite answer to technical professionals. Validation is required. That is why Magnetic Shield Corporation has developed practical methods of evaluating performance. Evaluation begins with our Co-NETIC® Slide-Rule Calculator to determine alloy thickness required to attenuate unwanted fields. However, the slide-rule is based on mathematics derived for specific cylindrical shaped shields; therefore it is necessary to further evaluate using our "hands-on" developmental Lab Kits to provide real evidence of success.
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Online Calculator - Shield Size Vs. Source Field Strength
How do you determine field reduction (attenuation) ratios of different thicknesses of shielding alloy? The first thing to do is estimate the physical size (diameter in inches) of a cylinder required to separate the area you need to protect from the source. Then, measure the source field strength (HO) in Gauss, and enter the data below.
To determining possible attenuation ratios (A), we have developed an automated, online calculator. Simply input the estimated shield size (diameter in inches) and measured source field strength (gauss value); then click on the calculate button. The online calculator will return possible attenuation ratio values for various shielding alloy thicknesses. Now you can see the thickness of material required, and its effectiveness (attenuation ratio).
Over several decades, Magnetic Shield Corporation has performed hundreds of laboratory tests and calculated thousands of shielding equations - all in an effort to continually validate the theoretical application of magnetic interference control in both AC and DC applications, and to aid engineers in shield design. Theory behind the B-H curve is well documented, and it remains an effective reference tool. By use of the B-H curve, our shielding alloys MuMETAL®, Co-NETIC® and NETIC® have been developed and refined to offer the most effective shielding characteristics for a variety of applications and markets. The B-H curve (below) depicts our materials' capabilities to attenuate and absorb a wide range of magnetic fields. For a spreadsheet version of our BH curve please contact us.
Radio Frequency (RF) Shielding
Our alloys provide interference control of H-fields, DC or AC to 100 kiloHertz, and differ fundamentally from RF shielding. Shielding for E-fields at radio frequencies (RF) above 100 kiloHertz involves use of high conductivity materials such as Copper, Aluminum or certain conductive coatings. Because MuMETAL®, Co-NETIC® and NETIC® alloys are also conductive, they can shield high frequency (RF) fields, even though they are formulated specifically for low frequency magnetic fields. When both high frequency and low frequency fields are present, our alloys may be most effective if grounded and designed with proper RF shielding practices.
When it comes to magnetic shielding, remember: "Theory is one thing, practicality is another, evaluation is everything."
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