When discussing electrolytic capacitors, it is crucial to explore their functions. This article will delve into two key roles played by electrolytic capacitors in circuit design, namely the filtering effect and the coupling effect.

1. Filtering Effect:
   In power supply circuits, the rectifier circuit converts AC into pulsating DC. To stabilize this pulsating voltage, a large-capacity electrolytic capacitor is connected after the rectifier circuit. It utilizes its charge and discharge characteristics (energy storage effect) to convert the pulsating DC voltage into a relatively stable DC voltage. However, to effectively filter out high-frequency and pulse interference signals, large-capacity electrolytic capacitors are generally accompanied by smaller capacitors (0.001–0.1µF) connected in parallel at both ends. These smaller capacitors help filter out high-frequency signals and pulse interference, as large-capacity electrolytic capacitors alone are not proficient in doing so due to their inherent inductance.
2. Coupling Effect:
   To prevent the front and rear circuits from affecting each other’s static operating points during low-frequency signal transmission and amplification, capacitive coupling is commonly employed. Electrolytic capacitors with larger capacities are usually preferred to minimize the loss of low-frequency components within the signal.
   Understanding the Judgment of Electrolytic Capacitors:
   Common electrolytic capacitor faults include capacity reduction, capacity disappearance, breakdown short-circuit, and leakage. Capacity reduction is caused by the gradual drying of the electrolyte over time, while breakdown and leakage generally occur due to high voltage or poor quality. The quality of electrolytic capacitors can be determined through various methods, including measuring resistance with a multimeter. By short-circuiting the two pins of the capacitor using the black test lead of the multimeter, the resistance indication value can help identify capacitors that are leaking or have broken down and short-circuited.
   Precautions in the Use of Electrolytic Capacitors:
3. Observe the proper polarity: Electrolytic capacitors have positive and negative polarities, and connecting them in the wrong orientation can severely compromise their functionality. Ensure that the positive pole is connected to the appropriate terminal according to the circuit requirements.
4. Work within voltage limits: Do not exceed the allowable working voltage of the electrolytic capacitor. Account for voltage fluctuations and leave a margin when designing the circuit.
5. Avoid excessive heat: Electrolytic capacitors should be placed away from high-power heating elements to prevent rapid evaporation of the electrolyte.
6. Non-polar capacitor arrangement: When filtering signals with both positive and negative polarity, consider connecting two electrolytic capacitors in series with the same polarity as a non-polar alternative.
7. Ensure isolation: The capacitor’s shell, auxiliary lead-out terminals, positive and negative electrodes, and circuit boards must be fully isolated to prevent any unwanted electrical interference.
   Conclusion:
   Electrolytic capacitors play a significant role in circuit design, particularly in filtering pulsating DC voltages and preventing interference among low-frequency signals. Understanding the judgment methods and adhering to precautions while using these capacitors are essential for ensuring optimal circuit performance.