【description】：capsun tells you how to quickly and accurately detect the quality of aluminum electrolytic capacitors.
1. because the capacity of aluminum electrolytic
capacitor is much larger than that of fixed
capacitor, the appropriate range should be selected according to different capacity. according to experience, in general, the capacitance between 1 and 47 μ f can be measured in rx1k gear, and that in excess of 47 μ f can be measured in rx100 gear.
2. connect the metal measuring rod of the red ammeter with the negative electrode and the metal measuring rod with the positive electrode. at the moment of contact, the pointer of the multimeter will deflect to the right with a large deflection (for the same electrical barrier, the greater the capacity, the greater the swing amplitude), and then gradually turn left until it stops at a certain position. at this time, the resistance 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 capacitor should be more than several hundred kq, otherwise it will not work normally. if the measured resistance is zero or the capacitance is not broken down in the positive direction, it means that if the resistance is too small to be tested, it means that it can not be broken down again.
3. for the electrolytic capacitor with unknown positive and negative marks, the above method of measuring leakage resistance can be used to distinguish. that is, first measure the leakage resistance arbitrarily, remember its size, and then exchange the metal measuring rod of the ammeter to measure a resistance value. in the two measurements, the one with high resistance is the positive connection method, that is, the metal measuring rod of the black meter is connected with the positive pole, and the metal measuring rod of the red meter is connected with the negative pole.
4. the capacity of electrolytic capacitor can be estimated according to the amplitude of pointer swing to the right.
5. measure the discharge speed of capacitance
use a digital multimeter to connect the two ends of the capacitor to charge first, then open the circuit to measure the speed of the voltage falling down. because the capacitor is open circuit, the only power consumption is the leakage current. if you measure the curve of voltage and time, you can deduce the leakage current. remember to use a better digital multimeter, because the input impedance of the multimeter itself is limited, and if it is of good quality the capacitance leakage current is not large, so the digital multimeter with smaller input impedance is not accurate.
6. attention! when measuring large capacity capacitance, if negative back and forth measurement is needed, the capacitor should be short circuited and discharged to avoid damaging the meter head.
according to experience, in high-frequency circuit, there are many small capacitors in switching power supply circuit, which can not be correctly judged by ordinary multimeter, and some capacitance may increase. it is strongly recommended to use special digital capacitance meter for measurement.
