SMD electrolytic capacitors, the cathode material used is electrolyte, which is a widely used capacitor that we see.

Polarized electrolytic capacitors are usually used in power supply circuits or intermediate frequency and low frequency circuits for power supply filtering, decoupling, signal coupling, time constant setting, and DC blocking. Generally, it cannot be used in AC power circuits. When used as filter capacitors in DC power circuits, its anode (positive) should be connected to the positive terminal of the power supply voltage, and the cathode (negative) should be connected to the negative terminal of the power supply voltage. , Otherwise it will damage the capacitor. Non-polar electrolytic capacitors are usually used in speaker frequency divider circuits, TV S correction circuits and single-phase motor starting circuits.

Electrolytic capacitors are widely used in household appliances and various electronic products, with a large capacity range, generally 1~1000μF, and a rated working voltage range of 6.3~450V. Its disadvantages are medium loss, large capacity error (the maximum allowable deviation is +100%, -20%), poor high temperature resistance, and prone to failure due to long storage time. The polarity of the electrolytic capacitor, pay attention to the "-" on the side of the electrolytic capacitor, which is the negative electrode. If the positive and negative electrodes are not marked on the electrolytic capacitor, you can also judge by the length of its pins. The positive electrode of the electrolytic capacitor is connected to the power supply. (The black test pen when the electricity is blocked), when the negative terminal is connected to the negative power supply (the red test pen when the electricity is blocked), the leakage current of the electrolytic capacitor is small (the leakage resistance is large). On the contrary, the leakage current of the electrolytic capacitor increases (the leakage resistance decreases).

When measuring, first assume that a certain pole "+" pole is connected to the black test pen of the multimeter, and the other electrode is connected to the red test pen of the multimeter, and record the scale where the needle stops (the resistance value of the needle to the left is large), and then The capacitor is discharged (that is, the two leads are touched), the two test leads are reversed, and the measurement is performed again. In the two measurements, the black test lead is connected to the positive electrode of the electrolytic capacitor when the last position of the needle is left (large resistance).