Abstract: Without special instruments, the quality and condition of a capacitor can be tested and judged using the resistance setting of a multimeter. Keywords: Capacitor testing method. Without special instruments, the quality and condition of a capacitor can be tested and judged using the resistance setting of a multimeter. For fixed capacitors with large capacitance (above 1μF), the resistance setting (R×1000) of a multimeter can be used to measure the two electrodes. The meter needle should swing towards the direction of lower resistance and then slowly swing back to near ∞. Then, the test probes are swapped and the test is repeated. The larger the swing, the larger the capacitance. If the test probes continuously touch the capacitor leads, the meter needle should point near ∞. Otherwise, it indicates leakage in the capacitor. The smaller the resistance value, the greater the leakage, and the poorer the capacitor's quality. If the meter needle does not move at all during measurement, it indicates that the capacitor is faulty or open-circuited. If the meter needle swings but cannot return to the starting point, it indicates that the capacitor has a large leakage and is of poor quality. For capacitors with small capacitance, the multimeter needle may not move when measured. In this case, an external DC voltage can be applied, and the multimeter can be used in DC voltage mode. The method is shown in Figure 1: set the multimeter to the appropriate DC voltage range, connect the negative (black) test probe to the negative terminal of the DC power supply, connect the positive (red) test probe to one end of the capacitor being tested, and connect the other end to the positive terminal of the power supply. A properly functioning capacitor should exhibit a large needle swing when the power is switched on; the larger the capacitance, the larger the needle swing. After the swing, the needle should gradually return to zero. If the multimeter needle does not swing when the power is switched on, the capacitor is faulty or open-circuited. If the needle continuously indicates the power supply voltage without swinging, the capacitor is short-circuited. If the needle swings normally but does not return to zero, the capacitor has leakage; the higher the indicated voltage, the greater the leakage. It should be noted that the auxiliary DC voltage used to measure small capacitors must not exceed the capacitor's withstand voltage to avoid damaging the capacitor during measurement. To accurately measure the capacitance of a capacitor, a capacitance bridge or Q meter is required. The simple testing methods described above can only provide a rough assessment of the capacitor's condition.