I teach you how to read inductance (II)

The role of the inductor in the circuit:

Basic role: filtering, oscillation, delay, notch, etc.

Image said: "through DC, blocking communication"

Detailed explanation: In the electronic circuit, the inductor coil acts on the AC finite current, and it can form a high-pass or low-pass filter, a phase shift circuit and a resonant circuit with a resistor or a capacitor; the transformer can be AC-coupled, transformed, and changed. Flow and impedance transformations, etc.

It is known from the inductive reactance XL=2πfL that the larger the inductance L is, the higher the frequency f is, and the larger the inductive reactance is. The voltage across the inductor is proportional to the inductance L, and also the electrical change speed Δi/Δt

The inductor coil is also an energy storage component that stores electrical energy in the form of magnets. The amount of stored energy can be expressed as: WL = 1/2 Li2. It can be seen that the larger the inductance of the coil, the larger the flow, and the more energy is stored.

Inductance symbol:

Nominal of inductance: straight standard, color ring standard, non-standard

Inductance directionality: no direction

Check the inductance or not: use the inductance meter to measure its inductance; use a multimeter to measure its on-off, the ideal inductance is very small, almost zero.

Common magnetic core ring:

Iron powder core series

Materials are: -2 (red / transparent), -8 (yellow / red), -18 (green / red), -26 (yellow / white), -28 (grey / green), -33 (gray/yellow), -38 (grey/black), -40 (green/yellow), -45 (black), -52 (green/blue); size: outer diameter from 30 to 400D (Note: OD from 7.8mm to 102mm).

Iron silicon aluminum series

The main u values are: 60, 75, 90, 125; size: outer diameter from 3.5mm to 77.8mm. In addition to the main ring shape, the specifications of the two products are E-shaped, rod-shaped, etc., and can also be customized according to various parameters provided by customers. They are widely used in computer motherboards, computer power supplies, power supplies, mobile phone chargers, lighting transformer dimmers, uninterruptible power supplies (UPS), various home appliance control panels, and more.

What is the connection and difference between the inductor and the magnetic bead:

The inductor is an energy storage component, and the magnetic beads are energy conversion (consumption) devices;

Inductors are mostly used in power supply filter circuits, and magnetic beads are mostly used in signal loops for EMC countermeasures;

Magnetic beads are mainly used to suppress electromagnetic radiation interference, while inductors are used in this respect to focus on suppressing conducted interference. Both can be used to handle EMC and EMI issues. There are two ways of EMI, namely: radiation and conduction, and different approaches use different suppression methods. The former uses magnetic beads, the latter uses inductance;

Magnetic beads are used to absorb ultra-high frequency signals. Like some RF circuits, PLLs, oscillator circuits, and ultra-high frequency memory circuits (DDR SDRAM, RAMBUS, etc.), it is necessary to add magnetic beads to the input part of the power supply. Energy component, used in LC oscillator circuit, low-frequency filter circuit, etc., its application frequency range rarely exceeds 50MHZ;

Inductors are commonly used for circuit matching and signal quality control. General connection and power connection. Magnetic beads are used where analog ground and digital ground are combined. Magnetic beads are also used for the signal lines;

Inductance measurement:

Two types of instruments for inductive measurement: RLC measurement (three types of resistance, inductance, capacitance can be measured) and inductance measuring instrument.

Inductance measurement: no-load measurement (theoretical value) and measurement (actual value) in the actual circuit.

Because the actual circuit used by the inductor is too much, it is difficult to classify. So we will explain the measurement under no-load conditions.

Inductance measurement steps: (RLC measurement is familiar with the operating rules of the instrument (instructions for use), and precautions.

Turn on the power and prepare for 15~30 minutes;

Select the L file and select the measured inductance;

Clamp the two clips together and reset them to zero;

Clamp the two clips at the ends of the inductor, read the value and record the inductance;

Repeat steps 4 and 5 to record the measured values. Have 5~8 data;

Compare several measured values: if the phase difference is not large (0.2uH), take the average value, remember the theoretical value of the inductor; if the phase difference is too large () 0.3 uH), repeat steps 2 to 6 until the theoretical value of the inductor is taken. ;

There are some discrepancies in the inductance parameters that can be measured by different instruments. So, be familiar with your measuring instrument before making any measurements. What can your instrument do. Then follow the instructions for it to do;

Intentions for the inductor during use:

Where the inductor is used

Wet and dry, the temperature of the environment, high-frequency or low-frequency environment, the inductance should be expressed inductive, or impedance characteristics, etc., should pay attention.

Frequency characteristics of the inductor:

At low frequencies, the inductor generally exhibits an inductive characteristic, which only functions to store energy and filter high frequencies.

However, at high frequencies, its impedance characteristics are very obvious. There are energy consumption and heat, and the inductive effect is reduced. The high frequency characteristics of different inductors are different.