The measurement method of using a digital multimeter to measure the quality of a capacitor
Set the range switch of the digital multimeter to the appropriate range in the capacitance mode. Then insert the red and black test leads of the multimeter into the Cx jack and the COM jack of the multimeter respectively (for the convenience of taking pictures, test leads with alligator clips are used here instead of the test leads). Then, let the red and black test leads contact the two pins of the capacitor respectively (when measuring an electrolytic capacitor, the polarity doesn't matter). If the value displayed on the multimeter is close to the nominal value of the capacitor (generally, an error of 5% - 10% is allowed), it indicates that the capacitor is in good condition.
When measuring a 47 μF electrolytic capacitor with the capacitance mode of the multimeter, the actually displayed capacitance is 45.17 μF. Since the error is within the specified range, it shows that the capacitor is good.
When measuring a good CBB capacitor with a nominal value of 0.1 μF/630V using the capacitance mode of the multimeter, the actually displayed capacitance is 0.1037 μF.
For a capacitor damaged by breakdown, the resistance between its two pins is very small. When measuring it with the capacitance mode of the multimeter, the meter will display "1", which means an overflow. Therefore, when measuring a capacitor, if the range switch of the multimeter is set correctly but the meter displays "1", it indicates that the capacitor is likely to be damaged by breakdown or has a large leakage current (at this time, the resistance value can be measured with the resistance mode of the multimeter to confirm whether it is damaged).
For electrolytic capacitors that have been stored for a long time, the electrolyte inside some capacitors will gradually dry up, making their capacitance very small. Therefore, when measuring an electrolytic capacitor, if the displayed capacitance is significantly lower than its nominal value, the capacitor is generally not suitable for use. As shown in the above picture, for a 100 μF electrolytic capacitor that has been stored for several years, its actually measured capacitance is only 54.08 μF.
A multimeter can be used to distinguish whether a capacitor is good or bad. Three methods are provided for your reference. Before measurement, the capacitor needs to be discharged, which will not be repeated below.
