To test the capacity of a capacitor, use a dedicated capacitor test meter or a multimeter with UF oscillation on the dial to test. Place the hands of the meter on the two short sides of the capacitor and check the displayed parameters on the dial. If the measured value is greater or less than the actual capacity of the capacitor nameplate by plus or minus 5%, it indicates that the capacitor has been damaged.
Without special instruments, the quality and quality of capacitors can be tested and judged using the resistance range of a multimeter. Fixed capacitors with large capacity (above 1 μ F) can be measured with the resistance range (R × 1000) of a multimeter to measure the two electrodes of the capacitor. The pointer should swing towards the direction of lower resistance, and then slowly swing back to the vicinity of ∞. Then exchange the test rod and try again to observe the oscillation of the hands. The larger the oscillation, the greater the capacitance of the capacitor. If the test rod keeps touching the capacitor lead, the needle should point near ∞. Otherwise, it indicates that the capacitor has leakage. The smaller the resistance value, the greater the leakage, indicating poor quality of the capacitor; If the needle does not move at all during measurement, it indicates that the capacitor has failed or is open circuited; If the pointer swings but cannot return to the starting point, it indicates that the capacitor has a large leakage and poor quality.
For capacitors with small capacity, measuring with a multimeter often does not show the needle swing. In this case, an external DC voltage and a multimeter DC voltage range can be used for measurement. The method is shown in Figure 1, which is to adjust the multimeter to the corresponding DC voltage range, connect the negative (black) test rod to the negative pole of the DC power supply, connect the positive (red) test rod to one end of the tested capacitor, and connect the other end to the positive pole of the power supply.