Unlike resistors and capacitors, inductance coils do not have a full range of standard products. In particular, some high-frequency small inductors usually need to be designed and manufactured according to circuit requirements. 1. Small fixed reactors Small fixed reactors (color-coded inductors) refer to the reactors with magnetic cores manufactured by manufacturers, which are horizontal and vertical. The inductance is generally between 0.1uH ~ 3000mH, and the operating frequency is 10kHz ~ 200MHz. Small fixed reactors generally allow a relatively small current and a large DC resistance. It should not be used as a resonant circuit. 2. Pot-shaped magnetic core ring adopts pot-shaped magnet; reactor made by Lu. With high permeability and inductance, it is usually used in LC filters and resonant circuits. The parameters of the reactor can be measured with special instruments, such as Q meter, digital bridge, etc. Use a multimeter to electrically block and measure the resistance of the coil to roughly judge its quality (note; the multimeter should be ohm-zeroed first). Generally, the DC resistance of the inductive coil should be very small (from a few ohms to tens of ohms). When the measured wire reading resistance is infinite, it indicates that the inside of the coil or the leading end has been disconnected. Usb Charger,Usb Charger Adapter,Usb Charger Adapter Plug,Usb Port Travel Adapter Guang Er Zhong(Zhaoqing)Electronics Co., Ltd , http://www.poweradapter.com.cn