When choosing and using inductance coil, the first thing to think of inspection measurement of coil, then to judge the quality of the coil and the advantages and disadvantages. To accurately measure inductance coil inductance and quality factor Q, generally all need special instruments, and the test method is more complicated. In actual work, generally don't do this test, inspection and Q value of the coil on and off only the size of the judgment. Can use multimeter electric stop first measuring dc resistance of the coil, and then compared with the original fixed value or nominal value, if the measured value compared to the original value or nominal value increase many, even a pointer (resistance tends to infinity), can judge the coil wire break; If the measured resistance tiny, the judgement is serious short circuit (if it is hard to compare local short circuit). In both cases, which can determine the coil is bad, can't use. If the measuring resistance with the original uncertain or nominal resistance were similar, can determine the coil is good. This kind of situation, can according to the following conditions, to judge the quality of the coil that is the size of the Q value. Coil inductance phase at the same time, the dc resistance is smaller, the higher the Q value. The bigger the diameter of wire used and its Q value. If using the multi-strand wire winding, wire the more the number of shares, the higher the Q value; Coil skeleton (or core) the smaller the loss of the materials used, the higher Q value. For example, high silicon iron core, silicon steel sheet do the high Q value is the use of common silicon steel sheet in iron core; Coil distributed capacitance and leakage is smaller, the higher Q value. Such as, honeycomb type winding coil, the Q value is for high level wound, also higher than mess around; Coil shield, installation location surrounded by five metal components, the Q value is higher, on the contrary, the Q value is low. The nearer the coil shield or metal components, the Q value to reduce the more serious; For high frequency coil with magnetic core, the Q value is coreless is high; The wastage of the magnetic core is smaller, the higher Q value it has. In power supply filter used in the low frequency choke coil, the size of the Q value is not too important, and the size of the inductance L is larger influence on filtering effect. Note that the low-frequency choke coil in use, much larger by dc, to prevent magnetic saturation, inserted with the core requirements, make its have the air gap. In order to prevent the occurrence breakdown phenomenon, of a coil and iron core insulation between should comply with the requirements. So, before use should also test the insulation resistance between coil and iron core. For high frequency coil inductance L of the test is more trouble, is generally used in the circuit according to the effect the appropriate adjustments, to determine whether the inductance is appropriate. Money on multiple winding coil and the multimeter test for a short circuit between the winding coil; With iron core and the metal shield of the coil to measure the winding and iron core or whether short circuit between the metal shield. SN65240PWR