Digital multimeter measurement of capacitance good or bad measurement method
Adjust the range switch of the digital multimeter to the appropriate range of the capacitance range, and then insert the red and black test leads of the multimeter into the Cx jack and COM jack of the multimeter respectively (for the convenience of taking pictures, the test leads with alligator clips are used here instead of the test leads), and then The red and black test leads touch the two pins of the capacitor respectively (if the electrolytic capacitor is measured, the polarity does not need to be distinguished). At this time, if the value displayed by the multimeter is close to the nominal value of the capacitor (generally an error of 5% to 10% is allowed) , it means that the capacitor is good.
The capacitance setting of the multimeter measures a 47μF electrolytic capacitor. The actual displayed capacity is 45.17μF. The error is within the specified range, indicating that the capacitor is good.
For a capacitor that is damaged by breakdown, the resistance between its two pins is very small. At this time, use the multimeter capacitance setting to measure, and the meter will display "1", that is, overflow. Therefore, when measuring the capacitance, if the multimeter range switch position is not turned Wrong, but the meter displays "1", it means that the capacitor is likely to be damaged by breakdown or the leakage is too large (at this time, you can use the resistance range of a multimeter to measure its resistance to confirm whether it is damaged).
For electrolytic capacitors left for a long time, the electrolyte inside some 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 picture above shows a 100μF electrolytic capacitor that has been stored for several years. The measured capacity is only 54.08μF.
You can use a multimeter to identify the quality of a capacitor. Three methods can be provided for your reference. The capacitor needs to be discharged before measurement, which will not be repeated below.
1. Direct measurement
If the measured capacitance is smaller than the maximum range of the multimeter, you can use the multimeter to measure it directly. If the capacitance is normal, the corresponding capacity will be displayed on the multimeter's display. The measured capacity can be compared with the marked capacitance. If this If the two are equal or relatively close, it can be determined that the capacitor is good.
2. Diode gear measurement
If the capacitance size you want to identify exceeds the range of the multimeter, you need to use the diode setting of the multimeter. Also connect the test leads to both ends of the capacitor. If you see the number on the dial increasing continuously, and the larger the capacitance, this phenomenon The more obvious it is, then it can be concluded that the measured capacitance is also good.
3. Resistance level measurement
This method is very similar to the second method. It can be used when the capacitance exceeds the range of the multimeter. First, turn the meter needle to the resistance position, and then connect the meter needle to both ends of the capacitor. If you can see the number on the multimeter dial, It keeps increasing. The larger the capacitance, the slower it increases. Then you can judge that the capacitor is good. If the number 1 is always displayed on the dial, then the capacitor is broken.
