1. The detection of safety regulation capacitor requires connecting the red lead of the multimeter to the negative pole and the black lead to the positive pole. At the moment of contact, the pointer of the multimeter deflects to the right with a large deviation. For the same electric block, the greater the capacity, the greater the swing, and then gradually turn left until it stops at a certain position. At this time, the resistance value is the forward leakage resistance of the safety capacitor, which is slightly greater than the reverse leakage resistance.

2. The actual use experience shows that the leakage resistance of the capacitor should generally be more than several hundred k Ω, otherwise, it will not work normally. In the test, if there is no charging phenomenon in the forward and reverse directions, that is, the meter needle does not move, it means that the capacity disappears or the internal circuit is open; If the measured resistance value is very small or zero, it means that the capacitor has large leakage or has been broken down and cannot be used again.

3. Gently rotate the rotating shaft by hand. It should feel smooth, and should not feel loose, tight and stuck sometimes. When the load shaft is pushed forward, backward, up, down, left and right, the rotating shaft shall not be loose.

4. Rotate the rotating shaft with one hand, and touch the outer edge of the film group with the other hand gently, without feeling loose. The variable capacitor with poor contact between the rotating shaft and the moving piece cannot be used any more.

5. Place the multimeter in R × At 10k gear, one hand connects the two probes to the movable and fixed end of the variable capacitor respectively, and the other hand slowly rotates the rotating shaft several times. The multimeter pointer should not move at infinity. In the process of rotating the shaft, if the pointer sometimes points to zero, there is a short circuit between the moving piece and the fixed piece; If a certain angle is encountered, the reading of the multimeter is not infinite, but some resistance values appear, indicating that there is leakage between the moving and fixed parts of the variable capacitor.