Inductors are generally coils wrapped with enameled round copper wire on a cylindrical frame. According to the different frequencies used, the material of the coil inner core is determined. Silicon steel sheet is generally used for low frequency, and soft ferrite (also known as iron oxide and magnetic porcelain) is generally used for intermediate frequency. Applications in various frequency ranges include: silicon steel sheets are used at 10 Hz ~ 1 kHz, and 1 kHz ~. Nickel-zinc ferrite for 2 MHz ~ 20 MHz, carbon-based ferrite for 20 MHz ~ 50MHz, and hollow core or brass core for high frequency above 50MHz (for adjusting inductance).
The main parameter of inductance is inductance (L), and the unit is Henry (H), which is defined as: when the current in the inductance changes 1 amp per second, the voltage across the inductance changes 1 volt, and its inductance is 1 Henry. Generally, the inductance exceeding 1H is a large inductance with the core inserted into the silicon steel sheet. This part is called "choke" and looks like a transformer, but it has only one coil and two terminals, so it can't be used as a transformer. Small inductance is called color code inductance, which is represented by color ring. Its expression is exactly the same as resistance, except that the basic unit is neither ohm (ω) nor Henry (h), but micro-heng (? H). Convert to:
1 Henry (H)= 1 000 mh = 1 000,000 mh (? h)
The specific reading method is: from left to right, three color rings represent inductance, the first ring represents the first digit, the second ring represents the second digit, the third ring represents the number of zeros behind, and the fourth ring represents the error percentage. The numbers represented by various colors are: black 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, purple 7, gray 8, white 9, silver 0.0 1 or 10%, and gold 0. 1 or 5%. For example, red, silver and silver represent 2.2 micro-henries10%; Rayna Sue brown gold, representing 5% error of 470 micro-hens; Blue-gray-red-silver, representing 6.8 millihends, with an error of10%; Brown, black and gold represent the 5% error of 100 millihends.
Inductance is almost the same as resistance in appearance. Which of the four cycles is the first? I'll tell you the solution: measure the resistance with a multimeter. Resistance is resistance, and resistance without resistance (resistance is 0) is inductance. In addition, the question about which is the first ring: the last ring of the color-coded inductor is either gold or silver, but the first ring can't be gold or silver, so it's easy to distinguish: either gold or silver is the first ring.