The DC resistance of the coil can be measured using the multimeter resistance stop first, and then compared with the original determined resistance value or nominal resistance value, if the measured resistance value is much larger than the original determined resistance value or nominal resistance value, or even the pointer is not moving (resistance value tends to infinity X), the coil can be judged to be broken; If the measured resistance value is very small, it is difficult to determine that it is a serious short circuit or a local short circuit. In these two cases, it can be determined that the coil is bad and cannot be used. If the detected resistance is not much different from the original determined or nominal resistance value, the coil can be judged to be good.

In this case, we can judge the quality of the coil, that is, the size of the Q value, according to the following circumstances. When the inductance of the coil is the same, the smaller the DC resistance, the higher the Q value; The larger the diameter of the wire, the larger the Q value. If multi-strand wire winding is used, the more strands of the conductor, the higher the Q value; The smaller the loss of the material used in the coil skeleton (or iron core), the higher its Q value.

For example, when the high-silicon silicon steel sheet is used as the iron core, its Q value is higher than that when the ordinary silicon steel sheet is used as the iron core; The smaller the coil distribution capacitance and magnetic leakage, the higher the Q value. For example, the Q value of a honeycomb winding coil is higher than that of a flat winding and higher than that of a disorderly winding. When the coil has no shield and there is no metal component around the installation position, its Q value is higher, and on the contrary, the Q value is lower. The closer the shield or metal component is to the coil, the more serious the Q value decrease; The location of the magnetic core should be properly arranged and reasonable; The antenna coil and the oscillation coil should be perpendicular to each other, which avoids the effect of mutual coupling.