Application of Multimeters in Electrolytic Capacitor Detection and Precautions
1. Measurement of leakage resistance of electrolytic capacitors
Select the appropriate range of the multimeter, connect the black probe to the positive pole of the electrolytic capacitor and the red probe to the negative pole of the electrolytic capacitor. Swing the pointer towards the direction where the resistance is zero. After a certain amplitude, swing it in the opposite direction towards infinity until it stops at a certain position. At this point, the resistance value referred to is the forward leakage resistance of the electrolytic capacitor. The larger the forward leakage resistance, the better the performance of the capacitor and the smaller the leakage current. Swap the two probes of the multimeter and measure again. The resistance value referred to at this time is the reverse leakage resistance of the electrolytic capacitor, which should be smaller than the forward leakage resistance.
For electrolytic capacitors with unclear positive and negative electrode markings, the method of measuring leakage resistance can be used to determine.
2. Performance testing of electrolytic capacitors
Common faults of electrolytic capacitors include leakage, open circuit, short circuit, etc. When using a multimeter to test their performance, the following steps should be followed: first, select the pointer type multimeter in the resistance range (R * 1K or R * 100), short-circuit the two probes to zero the ohm; Then contact the black and red probes of the multimeter with the positive and negative pins of the capacitor respectively, and observe the deflection of the multimeter pointer.
If the pointer has a significant deviation and slowly returns to a position close to the starting position, it indicates that the quality of the capacitor is good and the leakage is small. If the pointer deviates to the zero ohm position and does not return, it indicates that there is a short circuit inside the capacitor. If the pointer has a certain deviation and stops at a certain point on the dial, it indicates that the leakage of the capacitor is large. If the pointer does not deflect, it indicates that there may be an open circuit or a small capacitance inside the capacitor, and the charging and discharging currents are too small to deflect the pointer.
2, Precautions
When using a pointer type multimeter to measure electrolytic capacitors, the following precautions should be taken:
1. Due to the charging and discharging process of capacitors during measurement, they must be discharged first after the first measurement before the second measurement can be carried out.
2. When testing capacitors in circuit boards, it is necessary to determine whether other components in the circuit affect the measurement results. Generally, in circuit measurements should be avoided as much as possible.
