What are the detection methods of capacitors? Electronic third party testing organization

Date：2022-09-05 15:29:37Views：675

Capacitor is a kind of device that can accommodate electric charges. It is one of the electronic components widely used in electronic equipment. It is widely used in circuit isolation, AC, coupling, bypass, filtering, tuning loop, energy conversion, control and so on. The detection of capacitors can be divided into three categories: the detection of fixed capacitors, the detection of electrolytic capacitors and the detection of variable capacitors. What are the detection methods of capacitors? Detection technology plays an important role in all walks of life. Through detection, we can ensure product quality to a certain extent.

1、 Detection of fixed capacitor

1. Detect small capacitors below 10PF. Since the capacity of fixed capacitors below 10PF is too small, use a multimeter to measure them, and only qualitatively check whether there is leakage, internal short circuit or breakdown. Multimeter R can be selected for measurement × 10K gear, use two probes to connect two pins of the capacitor at will, and the resistance should be infinite. If the measured resistance (the pointer swings to the right) is zero, it indicates that the capacitor is damaged by leakage or internal breakdown.

2. Test 10PF ～ 0.01 μ F check whether the fixed capacitor is charged, and then judge whether it is good or bad. R is selected as the multimeter × 1K gear. Two triodes β The values are all above 100, and the penetration current can be composed of 3DG6 and other silicon triodes. The red and black probes of the multimeter are respectively connected to the emitter E and collector C of the composite tube. Due to the amplification effect of the composite triode, the charging and discharging process of the measured capacitance is amplified, so that the swing range of the multimeter pointer is increased, which is convenient for observation. It should be noted that during the test operation, especially when measuring the capacitance of small capacity, it is necessary to repeatedly exchange the measured capacitance pin contact points a and B, so that the swinging of the multimeter pointer can be clearly seen.

3. For 0.01 μ For fixed capacitance above F, R of multimeter can be used × 10K gear directly tests whether the capacitor has charging process and internal short circuit or leakage, and can estimate the capacity of the capacitor according to the amplitude of the pointer swinging to the right.

2、 Detection of electrolytic capacitors

1. Because the capacity of electrolytic capacitor is much larger than that of general fixed capacitor, appropriate measuring range shall be selected for different capacities during measurement. According to experience, in general, 1 ～ 47 μ Capacitance between F, R × 1K gear measurement, greater than 47 μ The capacitance of F can be r × 100 gear measurement.

2. Connect the red probe of the multimeter to the negative electrode and the black probe to the positive electrode. At the moment of contact, the pointer of the multimeter will deflect to the right by a large deflection (for the same electrical barrier, the larger the capacity, the larger the swing), and then turn to the left gradually until it stops at a certain position. The resistance at this time is the forward leakage resistance of the electrolytic capacitor, which is slightly larger than the reverse leakage resistance. Practical experience shows that the leakage resistance of electrolytic capacitor should be more than several hundred K Ω, otherwise, it will not work normally. In the test, if there is no charging in the forward and reverse directions, that is, the needle does not move, it means that the capacity disappears or the internal circuit is open; If the measured resistance is very small or zero, it means that the capacitor has large leakage or has been broken down and damaged, and can not be used again.

3. For electrolytic capacitors with unknown positive and negative marks, the above method of measuring leakage resistance can be used to identify them. That is, measure the leakage resistance at will, remember its size, and then exchange the probes to measure a resistance value. The one with the largest resistance in the two measurements is the positive connection method, that is, the black probe is connected to the positive electrode, and the red probe is connected to the negative electrode.

4. The capacity of the electrolytic capacitor can be estimated by using the resistance gear of the multimeter and the method of charging the electrolytic capacitor in the forward and reverse directions, according to the swing range of the pointer to the right.

3、 Detection of variable capacitor

1. Gently rotate the rotating shaft by hand, and it should feel very smooth. It should not feel loose, tight or even stuck sometimes. When the load shaft is pushed forward, backward, up, down, left, right and other directions, the rotating shaft shall not be loose.

2. Rotate the rotating shaft with one hand and gently touch the outer edge of the moving piece group with the other hand, without any looseness. The variable capacitor with poor contact between the rotating shaft and the rotor can no longer be used.

3. Place the multimeter in R × At 10K gear, connect the two probes to the leading ends of the moving piece and the fixed piece of the variable capacitor respectively with one hand, and slowly rotate the rotating shaft several times with the other hand. The multimeter pointer should not move at infinity. In the process of rotating the shaft, if the pointer sometimes points to zero, it indicates that there is a short circuit between the moving piece and the stator; If the reading of the multimeter is not infinite but has a certain resistance at a certain angle, it indicates that there is leakage between the moving piece and the fixed piece of the variable capacitor.

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