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. Since the actual circuit used by the inductor is too much, it is difficult to classify it. Only the measurements under no-load conditions are explained. Inductance measurement step (RLC measurement):
1. Familiar with the operating rules of the instrument (instructions for use), and precautions.
2. Turn on the power and prepare for 15-30 minutes.
3. Select the L file and select the measured inductance.
4. Clip the two clips together and reset them to zero.
5. Hold the two clips at each end of the inductor, read the value and record the inductance.
6. Repeat steps 4 and 5 to record the measured values. Have 5-8 data.
7. Compare several measured values: if the phase difference is not large (0.2uH), take the average value and remember the theoretical value of the inductor; if the phase difference is too large (0.3uH), repeat steps 2 - 6 until the theory of inductance is taken. value.
There are some discrepancies in the inductance parameters that can be measured by different instruments. Therefore, do any familiarity with the measuring instrument used before the measurement, understand what the instrument can do, and then follow the instructions given to it.
circuit diagram
Labeling method
Inductor
1. Straight standard method: directly mark the inductance of the inductor, the allowable error and the maximum operating current, etc., directly on the outer casing of the inductor coil.
2, color standard method: color standard method: that is, the color ring represents the inductance, the unit is mH, the first two digits represent the effective digits, the third digit represents the magnification, and the fourth digit is the error.
Good or bad judgment
1. Inductance measurement: Turn the multimeter to the buzzer diode and place the test leads on the two pins to see the reading of the multimeter.
2. Good or bad judgment: For the chip inductor, the reading at this time should be zero. If the multimeter reading is too large or infinite, the inductance is damaged.
For the number of turns of the inductor coil, the coil diameter of the coil will be several tens to hundreds of times. Usually, the DC resistance of the coil is only a few ohms. The damage is manifested as obvious damage to the hot or inductive magnetic ring. If the induction coil is not seriously damaged and cannot be determined, the inductance can be measured by the inductance meter or judged by the replacement method.
Precautions
1. Inductive components, the core and winding are easy to change due to the temperature rise effect. It should be noted that the body temperature must be within the specification range.
Second, the winding of the inductor easily forms an electromagnetic field after the current passes. When placing the component position, care should be taken to keep the adjacent inductors away from each other, or the winding groups are at right angles to each other to reduce the mutual inductance.
3. The windings of the layers of the inductor, especially the multi-turn thin wires, will also generate gap capacitance, which will cause high-frequency signal bypass and reduce the actual filtering effect of the inductor.
4. When testing the inductance value and Q value with the meter, in order to obtain the correct data, the test leads should be as close as possible to the component body..
Functional use editing
The inductor mainly plays the role of filtering, oscillation, delay, trapping, etc. in the circuit, as well as screening signals, filtering noise, stabilizing current and suppressing electromagnetic interference. The most common function of the inductor in the circuit is to form an LC filter circuit together with the capacitor. The capacitor has the characteristics of "resistance to DC, AC", while the inductor has the function of "DC, DC". If the DC current with many interference signals is passed through the LC filter circuit, the AC interference signal will be consumed by the inductor into heat energy; when the relatively pure DC current passes through the inductor, the AC interference signal is also turned into a magnetic sense. And thermal energy, the higher the frequency is the most easily inductive impedance, which can suppress higher frequency interference signals.
The inductor has the characteristic of preventing the passage of the alternating current and allowing the direct current to pass smoothly. The higher the frequency, the larger the impedance of the coil. Therefore, the main function of the inductor is to isolate, filter or form a resonant circuit with a capacitor or a resistor.
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