Pointer multimeter to detect electrolytic capacitors
1. Because the capacity of electrolytic capacitors is much larger than that of general fixed capacitors, appropriate measurement ranges should be selected for different capacities during measurement. Based on experience, in general, capacitors between 1 and 47 μ F can be measured in the R × 1k range, while capacitors greater than 47 μ F can be measured in the R × 100 range.
2. Connect the red probe of the multimeter to the negative terminal and the black probe to the positive terminal. At the moment of initial contact, the multimeter pointer will deflect significantly to the right (for the same electrical barrier, the larger the capacity, the greater the swing), and then gradually turn left until it stops at a certain position. At this point, the resistance value is the forward leakage resistance of the electrolytic capacitor, which is slightly greater than the reverse leakage resistance. Practical experience has shown that the leakage resistance of electrolytic capacitors should generally be above several hundred k Ω, otherwise they will not function properly. In the test, if there is no charging phenomenon in both forward and reverse directions, that is, the meter needle does not move, it indicates that the capacity has disappeared or there is an internal circuit breaker; If the measured resistance is very small or zero, it indicates that the capacitor has a large leakage or has been broken down and damaged, and cannot be used anymore.
3. For electrolytic capacitors with unclear positive and negative electrode markings, the above method of measuring leakage resistance can be used to distinguish them. First, measure the leakage resistance arbitrarily, remember its size, and then exchange the probes to measure another resistance value. The one with the highest resistance value between the two measurements is the forward connection method, where the black probe is connected to the positive pole and the red probe is connected to the negative pole.
4. Use a multimeter resistor to charge the electrolytic capacitor in both forward and reverse directions. Based on the magnitude of the pointer's rightward swing, the capacity of the electrolytic capacitor can be estimated.
