There are many ways to classify magnetic cores, and at present there are more numbering methods mainly by appearance. In the process of use, it is necessary to understand all aspects of the characteristics of the material in order to accurately determine whether the incoming material meets the requirements. Some materials have the same appearance size, color, inductance value, but it is two completely different materials, if the inspector has limited understanding, rash judgment will certainly lead to heavy losses.

a. Appearance: There are many kinds of cores according to their appearance, including ring (T-shaped), E-shaped, C-shaped, etc.

　　b. Coating: The coating of the magnetic ring plays a protective role for the ring. Usually, the manufacturer's numbering expresses the coating of the magnetic ring in English letters, with different letters indicating different coating thickness and different pressure resistance. This is specified on the numbering instructions below.

　　c. Material: In the case of the same size, the magnetic ring material is different, the inductance value of the ring is also different, there are more than a dozen parameters to characterize the material of the ring, as a feed inspection personnel, at least three of the parameters to understand.

　　ui value: Chinese means relative magnetic permeability, no unit. At present, the ui value of magnetic rings used by our company are: 850(1000), 4700(5000), 10000, etc. When the appearance and size of magnetic rings are exactly the same, the higher the ui value, the higher the inductance of magnetic rings. In addition, this parameter also characterizes the frequency characteristics, temperature characteristics, and losses of the ring.

　　AL value: AL value is defined as the single-turn inductance of the ring, and this parameter is directly used for the level sorting of the ring. The higher the ui value, the higher the AL value of the ring, when the rings have identical dimensions.

　　Current resistance: For the magnetic ring used in 100/1000BASE products, it is required to withstand a DC current of 8mA, which means that the magnetic ring used for these products needs to increase the DC8mA test when it is used for incoming inspection.