Capacitor Testing with a Multimeter and Corresponding Operating Procedures
The detection of capacitance mainly adopts substitution method and instrument detection method. The instrument detection method can use the capacitance range of a digital multimeter or a capacitance meter to measure the capacity of the tested capacitor, or use the resistance range of a pointer multimeter to detect the resistance of the capacitor to determine if it is normal. Because the capacitance of a digital multimeter is generally only measured within 20 μ F, capacitors exceeding 20 μ F should be detected using a capacitance meter, pointer multimeter, or substitution method.
1. Discharge of capacitors
If the capacitor being tested stores charges, the stored charges should be discharged first to avoid damaging the multimeter, capacitance meter, or causing electric shock and injury. When the measured capacitor stores a large amount of charge, the plug of the soldering iron can be used to touch the pin of the capacitor, and the internal resistance of the soldering iron can be used to release the voltage, which can reduce the discharge current; If the stored charge in the capacitor is small, the two pins of the capacitor can be short circuited using a multimeter probe or the metal part of a screwdriver to directly discharge the stored charge.
2. Use a digital multimeter to check the capacitance
The method of measuring capacitance with a digital multimeter is relatively simple. First, place the function switch in the capacitance range C (F), then insert the capacitor into the test stand, and the display screen will show the capacitance of the capacitor. If the value is less than the nominal value, it indicates a decrease in capacitance; If the value is greater than the nominal value, it indicates capacitor leakage.
As shown in the figure below, if the capacitance of the electrolytic capacitor to be measured is 10 μ F, place the multimeter in the 20 μ F range, and then insert the capacitor into the capacitor test seat. The display screen shows 10.14, indicating that the capacitance value of the capacitor is 10.14 μ F; If the capacitance needs to be measured to be 5600pF, place the multimeter in the 20nF range, and then insert the capacitor into the capacitance test stand. The display screen shows 5.52, indicating that the capacitance value of the capacitor is 5520pF.
3. Use a pointer type multimeter to check the capacitance
When detecting the capacitance of a pointer type multimeter in the resistance mode, the first step is to select the resistance mode of the multimeter based on the capacitance size. After discharging the stored capacitor, connect the red and black probes to the two pins of the capacitor respectively, and determine whether the capacitor is normal by the deflection angle of the probe. If the pointer quickly deflects to the right and then slowly returns to its original position to the left, generally speaking, the capacitor is good. If the pointer no longer rotates after swinging, it indicates that the capacitor has broken down. If the pointer gradually stays in a certain position after swinging, it indicates that the capacitor has leaked electricity; If the pointer cannot swing to the right, it indicates that the capacity of the measured capacitor is small or has no capacity. For example, when measuring a capacitance of 47 μ F, the first step is to select the R * 1K range. When two probes are connected to the two pins of the capacitor, the probe quickly deflects to the right due to the capacitor being charged, and then the capacitor slowly returns to the "0" position on the left due to discharge. This indicates that the capacitor is normal.
