Measuring method of leakage resistance of electrolytic capacitor
1. Select the appropriate range of the multimeter, connect the red test lead to the negative pole of the electrolytic capacitor, and connect the black test lead to the positive pole of the electrolytic capacitor. At this time, the hand is swung in the direction of R, and after swinging to a certain amplitude, it is reversed to the poor. The direction is swung until a certain position stops. At this time, the resistance value indicated by the pointer is the positive leakage resistance of the electrolytic capacitor. The larger the positive leakage resistance, the better the performance of the capacitor and the smaller the leakage current. Adjust the red and black test leads of the multimeter (the red pen is connected to the positive pole and the black test lead to the negative pole), and then measure. The resistance value indicated by the pointer is the reverse leakage resistance of the capacitor. This value should be smaller than the forward leakage resistance. . If the measured values of the two leakage resistors are small (several hundred kiloohms or less), the performance of the electrolytic capacitor is poor and cannot be used.
Because the capacity of electrolytic capacitors is much larger than that of general fixed capacitors, the appropriate range should be selected for different capacities when measuring. According to experience, in general, the capacitance between 1 ~ 47μF can be measured by R&TImes; 1k block, and the capacitance larger than 47μF can be measured by R&TImes;
For an electrolytic capacitor in which the positive and negative signs are unknown, the above method for measuring the leakage resistance can be used for discrimination. That is, first measure the leakage resistance arbitrarily, remember its size, and then exchange the test leads and then 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 is connected to the positive pole, and the red meter is connected to the negative pole.
2. Discrimination of positive and negative electrodes of electrolytic capacitors The method for judging the positive and negative electrodes of electrolytic capacitors is mainly based on the method of measuring the leakage resistance according to the above. Use the ohmic block of the multimeter to select the appropriate range according to the capacity of the electrolytic capacitor. Measure the leakage resistance of the two pins of the capacitor with two test leads, and record the magnitude of the resistance. Then adjust the leakage resistance of the two test leads. The value is compared with the measured leakage resistance value twice, and the leakage resistance value is small once, and the black test pen is in contact with the negative electrode of the electrolytic capacitor.
Pay attention to the following three points when testing capacitors with a multimeter:
1 Regardless of the measurement of the leakage resistance of the capacitor, or the measurement of the short circuit and the open circuit, it is necessary to pay attention to the fact that the hand cannot touch the two leads at the same time.
2Because the capacitor must be charged and discharged during the measurement process, after the first measurement, it must be discharged first (short the two leads of the capacitor with a multimeter) before the second measurement can be performed.
3 When testing the capacitors in the road, it is necessary to find out whether other components of the circuit affect the measurement results. In general, the road measurement should be avoided.