Commonly Used Testing Methods & Standards for
Magnets & Magnetic Assemblies
For more than 50 years, Integrated Magnetics has been a leading provider of custom magnets and magnetic assemblies. We design, engineer, and manufacture advanced magnetic solutions from sensor and high-temperature magnets, to Halbach arrays, magnetic yokes, and more. Request a quote or contact us for more information about custom technical magnets and magnetic assemblies.
Here are some of the more commonly used testing methods & standards for technical magnets and magnetic assemblies:
This test uses a gaussmeter to measure the flux density of a magnet at a determined distance. Typically, the measurement is made either at the magnet's surface or at the distance at which the flux will be used in the magnetic circuit. Flux density testing verifies that the magnet material used for our custom magnets will perform as predicted when the measurement matches the calculated values.
This test uses a Helmholtz coil to verify magnetic values. A Helmholtz coil is a pair of coils, each with known number of turns, placed at a determined distance from the magnet being tested. When a permanent magnet of known volume is placed at the center of both coils, the magnetic flux of the magnet produces a current in the coils which can be related to a measurement of flux (Maxwells) based on the displacement and number of turns.
By measuring the displacement caused by the magnet, the magnet volume, the permeance coefficient, and the recoil permeability of the magnet, we can determine values such as Br, Hc, BHmax and the orientation angles.
Helmholtz coils can be used to determine the relationship between the mechanical zero axis and the magnetic zero axis. This is accomplished by placing the magnet in the coil and measuring the flux output in three different axes. The perfectly aligned magnet will have a maximum displacement on the orientation axis, and a null displacement in either of the other two axes. As a displacement is measured in the other two directions, these can be used to calculate the angle variation by vector summation using C2= SQRT(A2+B2).
A permeameter can be used to trace all or a portion of the hysteresis loop of a material. A sample of the material to be tested is magnetized to saturation and then demagnetized while the flux output is measured and plotted in a closed-circuit condition. The resulting curve is the B-H curve for the material.
A Search Coil is a coil with a known number of turns, that is placed around a magnet. As the magnet is moved into and out of the coil, the lines of magnetic flux produced by the magnet produce a current in the coil. This current is integrated in the flux meter to provide a reading of the total flux emanating from the magnet.
Search coils are designed specifically for certain magnet geometries. They can be used to verify the saturation of magnets after the magnetizing process. Typical applications are motor and generator rotor assemblies.
A flux map of a magnet array, analogous to a geographical contour map, can be produced by scanning the array with a 3-axis Hall Effect probe and plotting the resulting data as a flux contour map. The data can be presented in many other ways, but the contour plot is a useful way of visualizing the effect of the magnet array.
Integrated Magnetics uses pull testing to determine the holding strength of our custom magnet assemblies. Holding strength is directly related to the square of the flux density and the magnetic gap between the assembly and the surface which it will adhere to.
Although there are various methods that can be used to verify this value, we have developed a simple test stand that allows our custom magnet assemblies to be pulled away from a 3" steel plate in a vertical motion. It is critical to the accuracy of the test that the assembly be pulled away evenly from the plate, and not lifted from one end first.
Integrated Magnetics wrote the specification (MDFA-101-95) for the standard methodology to be used when a pull test is required. This standard was adopted by the MDFA (Magnet Distributors and Fabricators Association) and published as the association's own standard.
Published by the Magnet Materials Producers Association (MMPA), the forerunners of the International Magnet Association, these standards are widely used today.
- MMPA Standard on Specifications for Permanent Magnet Materials
- MMPA PMS-88 Permanent Magnet Guidelines
Send us a request for quote or contact us today to discuss testing and verification for your custom magnets and magnetic assemblies, and our experienced team of engineers will help you determine the most cost effective way of providing you with a solution. We also offer a wide variety of stock permanent magnets available for on-line purchase at MagnetShop.com.Request A Quote Contact Us Form