1. Detect a small capacitor below 10pF. The capacity of a fixed capacitor below 10pF is too small. Use a multimeter to measure it. Only qualitatively check whether it has leakage, internal short circuit or breakdown. When measuring, you can use the multimeter R×10k block. Use two metal meter bars to connect the two pins of the capacitor. The resistance should be infinite. If the measured resistance value (the indicator swings to the right) is zero, it indicates that the capacitor leakage is damaged or internal breakdown.
How to judge whether the capacitor is good or bad?
2. For fixed capacitors above 0.01μF, use the R×10k block of the multimeter to directly test the capacitor for charging process and whether there is internal short circuit or leakage, and estimate the capacity of the capacitor according to the amplitude of the pointer swinging to the right.
How to detect the quality of electronic capacitors?
1. Because the capacity of electronic capacitors is much larger than that of general fixed capacitors, the appropriate range should be selected for different capacities when measuring. According to experience, under normal circumstances, the capacitance between 1 ~ 47μF can be measured by R × 1k block, and the capacitance larger than 47μF can be measured by R × 100 block. How to judge whether the capacitor is good or bad?
2. Connect the metal meter of the multimeter to the negative pole, and the metal meter of the black meter is connected to the positive pole. At the moment of contact, the pointer of the multimeter is deflected to the right with a large degree of skewness (for the same electrical block, the larger the capacity, the larger the swing ), then gradually turn left until it stops at a certain position. The resistance at this time is the forward leakage resistance of the electrolytic capacitor, which is slightly larger than the reverse leakage resistance. Practical experience shows that the leakage resistance of electrolytic capacitors should generally be several hundred kΩ or more, otherwise, it will not work properly. In the test, if there is no charging in the forward and reverse directions, that is, the hands are not moving, the capacity disappears or the internal circuit is broken; if the measured resistance is small or zero, the leakage of the capacitor is large or the breakdown is broken. Can no longer be used.
3. For electrolytic capacitors whose positive and negative signs are unknown, the above method for measuring leakage resistance can be used for discrimination. That is, first measure the leakage resistance arbitrarily, remember its size, and then exchange the meter metal rod to measure a resistance value. The one with a large resistance value in the two measurements is the forward connection method, that is, the black meter metal rod is connected to the positive pole, and the red meter metal rod is connected to the negative pole. How to judge whether the capacitor is good or bad?
4, using the multimeter electric block, using the method of positive and negative charging of the electrolytic capacitor, according to the size of the pointer to the right swing, the capacity of the electrolytic capacitor can be estimated.
5, measuring the speed of capacitor discharge Use a digital multimeter to charge both ends of the capacitor and then measure the voltage drop. The only thing that consumes power when the capacitor is open is the leakage current. If you measure the voltage versus time curve, you can reverse the leakage current. Remember to use a better digital multimeter, because the input impedance of the multimeter itself is limited. If the leakage current of a good quality capacitor is not large, the digital multimeter with a small input impedance is not allowed.
6, note! If you need to measure the positive and negative back and forth when measuring the large capacity capacitor, you should short-circuit the capacitor to avoid damage to the meter. According to experience, in high-frequency circuits, there are many small capacitors in the switching power supply circuit. The ordinary multimeter cannot correctly judge whether it is good or bad, and some capacitors may increase. It is highly recommended to measure with a dedicated digital capacitance meter.
Scource from: https://www.slw-ele.com/measure-small-capacitors.html