For permanent magnet materials, remanence, coercivity, intrinsic coercivity and maximum magnetic energy product are the most common four parameters to measure the performance of magnetic materials, in addition to the finished magnet we will often see another two parameters – surface magnetic and magnetic flux (also known as magnetic flux), they often appear in our magnet inspection report inside. So the magnet test meter magnetic and magnetic flux which is more accurate, or should be based on which parameters as the quality of the magnet or qualified or not? Let’s first introduce their concept.
Surface magnetism
The simple understanding of surface magnetism is the magnetic induction intensity of the surface, defined as the magnetic flux through the unit area, so it is also called the surface magnetic flux density, the unit is Gaussian Gs or Tesla T, the measuring instrument is a Gaussian meter or a test instrument with Hall chip.
Surface magnetic refers to a measuring point, to be exact, is a small measurement area of value, and the magnetic field distribution of the magnet is changing, so the surface magnetic at different points is generally different. For applications that require the use of space magnetic fields, the surface magnetic field or the magnetic induction intensity value at a specified point is usually regarded as an important technical requirement.
Table magnetic and magnet length-diameter ratio (the ratio of the height of the magnet to the diameter, here the default height or thickness is the magnetization direction of the magnet), the higher the high-diameter ratio, the higher the table magnetic, that is, the larger the magnetization direction size, the higher the table magnetic; The larger the surface area perpendicular to the direction of magnetization, the lower the surface magnetic field. In addition, the Hall components on the Gauss meter of different manufacturers are different, and the table magnetism measured by the same magnet is also slightly different.
Magnetic flux Φ
The definition of magnetic flux physics is perpendicular to a certain area through the magnetic field line, our simple understanding is to measure the overall magnetic size of the physical quantity, the unit is Wb, expressed by Φ, Φ=B×S, B represents the magnetic induction intensity, S represents the magnetic pole area, that is to say, the size of the magnetic flux depends on the magnetic pole area and magnetic induction intensity.
The measuring instrument of the flux is the flux meter, and the Helmholtz coil can not only measure the flux, but also calculate its magnetic moment, because the measurement value of the flux will change with the parameters of the flux meter and the Helmholtz coil. Magnetic flux and magnetic moment, like the difference between weight and mass, weight is affected by the gravitational constant, the weight of the same object on Earth and Mars is different, but the mass is the same. Similarly, affected by the number of turns of the coil, the magnetic flux results of different flux meters and coils measuring the same magnet may be different, but the magnetic moment of the magnet is the same.
So which is more accurate, magnetic or magnetic flux?
In general, we recommend that customers use the magnetic flux as a reference to evaluate the consistency of the same batch of magnet products. Because the measurement of the table magnetic is the Gaussian value of a certain point, even if the same magnet is measured by different inspectors and different times, it is likely to be not the same point, so the measured data results themselves have a large error. The measurement of magnetic flux is much more accurate. Therefore, we recommend using the magnetic flux as a reference for consistency and the surface magnetic as an auxiliary reference.
In general, the consistency of the magnetic flux of the same batch of magnets will be less than 3%, and the magnetic flux value between batches may also vary by about 1%. I hope the above information is helpful.
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