The measurement method for measuring the quality of capacitance using a digital multimeter
Methods for judging the quality of capacitors
Adjust the range switch of the digital multimeter to the appropriate range of the capacitor range, then insert the red and black probes of the multimeter into the Cx and COM sockets of the multimeter (for the convenience of taking photos, a test wire with a crocodile clip is used instead of the probe), and then the red and black probes touch the two pins of the capacitor separately (if measuring electrolytic capacitance, polarity can be ignored). If the value displayed on the multimeter is close to the nominal value of the capacitor (generally allowing 5% to 10% error), it indicates that the capacitor is good.
For a capacitor that has been damaged due to breakdown, the resistance between its two pins is very small. When measuring with a multimeter's capacitance range, the instrument will display "1", indicating overflow. Therefore, when measuring the capacitor, if the multimeter's range switch position is not set incorrectly, but the instrument displays "1", it is likely that the capacitor has been damaged due to breakdown or has too much leakage (at this time, the resistance value can be measured with a multimeter's resistance range to confirm whether it is damaged).
For electrolytic capacitors placed for a long time, some electrolytes inside the capacitors will gradually dry up, making their capacity very small. Therefore, when measuring electrolytic capacitors, if the displayed capacity is significantly lower than its nominal value, the capacitor is generally not suitable for use. The above figure shows a 100 that has been stored for several years μ The electrolytic capacitor of F has a measured capacity of only 54.08 μ F.
A multimeter can be used to distinguish the quality of a capacitor, and three methods can be provided for reference. Before measuring, it is necessary to discharge the capacitor, which will not be repeated in the following text.
1. Direct measurement
If the measured capacitance size is less than the maximum range of the multimeter, it can be directly measured using a multimeter. If the capacitance is normal, the corresponding capacity size will be displayed on the display screen of the multimeter. The measured capacity size can be compared with the marked capacitance size. If these two are equal or close, it can be determined that the capacitance is good.
2. Diode level measurement
If you want to distinguish whether the capacitance size has exceeded the range of a multimeter, you need to use the diode range of the multimeter. Similarly, connect the probe to both ends of the capacitor. If you see this number continuously increasing on the dial, and the larger the capacitance, the more obvious this phenomenon is, then it can be concluded that the measured capacitance is also good.
3. Resistance measurement
This method is similar to the second method, which can be used when the capacitance exceeds the range of a multimeter. First, turn the meter needle to the resistance range, and then connect the meter needle to both ends of the capacitor. If the number can be seen on the dial of the multimeter continuously increasing, and the capacitance increases slower as it increases, then it can be judged that the capacitor is good. If the number 1 is always displayed on the dial, then the capacitor is broken.
