Electrolytic capacitance is the capacitance with the oxide layer formed on the electrode by the action of electrolyte as the insulating layer, which usually has large capacity. Electrolyte is a liquid, jelly like substance rich in ions. Most electrolytic capacitors are polar, that is, when working, the positive voltage of the capacitor must always be higher than the negative voltage. The high capacity of electrolytic capacitor is obtained at the expense of many other characteristics, such as large leakage current, large equivalent series inductance and resistance, large capacitance error, short life, etc. This paper collects and sorts out some materials, hoping to be of great reference value to all readers.
There are two kinds of electrolytic capacitors in common use, one is aluminum electrolytic capacitor, the other is tantalum electrolytic capacitor.
The electrolytic capacitor has three important parameters: withstand voltage capacity and temperature. If it is not used for a long time or has been used for a long time, the electrolyte will dry up and the capacity will drop. At this time, it will not play its due role in the circuit and cause circuit failure.
There are several symptoms:
- Appearance deformation: it is the appearance of bulge, burst and liquid flow. This is easy to find. The solution is to replace it;
- Capacitance change value: most of them are because the capacity becomes smaller or there is no empty space, but it can not be seen from the appearance. At this time, online measurement can be made with a rough judgment (use a pointer meter to measure the charging and discharging time). However, because there may be other components in the circuit in parallel with it, there are uncertainties. It is better to remove or weld a pin for measurement;
- Capacitive short circuit: it is also easy to judge, and its resistance is very small or even zero when measured with a meter;