Lecture on Capacitor knowledge(IV)

Judging Capacitor quality by Multimeter. 
The capacitance of the apparent electrolytic capacitor is usually measured and judged by using the R × 10, R × 100 and R × 1K blocks of the multimeter. The red and black meter pens are respectively connected with the negative electrodes of the capacitors (before each test, the capacitors should be discharged, and the quality of the capacitors should be judged by the deflection of the gauge pins. If the watch needle is quickly set to the right, and then slowly back to the left in situ, generally speaking, the capacitor is good. If the watch needle does not turn again after the needle is set, the capacitor has been broken down. If the gauge needle is gradually returned to a certain position after setting up, then the capacitor has leakage. If the gauge needle can not be set, the capacitor electrolyte has dried up to push the loss of capacity. 
Some leakage capacitors, with the above method is not easy to accurately judge the good or bad. When the voltage value of capacitor is larger than that of battery voltage in multimeter, according to the characteristics of low leakage current in forward charging of electrolytic capacitor and large leakage current in reverse charge, R × 10K block can be used to reverse charge capacitor. It is observed whether the stopover of the gauge needle is stable (that is, whether the reverse leakage current is constant or not, so that the quality of the capacitor is judged and the accuracy is high. . Any watch needle in a certain position stay unstable or after staying slowly moving slowly to the right of the capacitor has leakage, can not continue to use. The needle generally stays and is stable in the range of 50-200 K scale