How do you measure a capacitor with a multimeter?
(1) Detection of fixed capacitors with a capacitance above 0.01 pF
Set the analog multimeter to the R×10k ohm range and perform ohm zero adjustment. Then, use the red and black test leads of the multimeter to touch the two pins of the capacitor respectively, and observe the movement of the multimeter's pointer, as shown in Figure 1.
If, at the moment the test leads are connected, the pointer of the multimeter swings slightly to the right and then returns to infinity, and after swapping the test leads and measuring again, the pointer also swings to the right and then returns to infinity, it can be determined that the capacitor is normal.
If, at the moment the test leads are connected, the pointer of the multimeter swings to near "0", it can be determined that the capacitor is broken down or has serious leakage.
If, at the moment the test leads are connected, the pointer swings and does not return to infinity, it can be determined that the capacitor has leakage.
If the pointer of the multimeter does not swing in both measurements, it can be determined that the capacitor is open - circuited.
(2) Detection of fixed capacitors with a capacitance less than 0.01 pF
When detecting small capacitors below 10 pF, since the capacitance is too small, using a multimeter for measurement can only check if there is leakage, internal short - circuit, or breakdown. When measuring, select the R×10k range of the multimeter and connect the two test leads to the two pins of the capacitor randomly. The resistance value should be infinity. If the measured resistance value is zero, it can be determined that the capacitor is damaged due to leakage or internally broken down.
(3) The following method can be used to detect fixed capacitors with a capacitance between 10 pF and 0.01 μF.
Set the multimeter to the R×10k range. Select two transistors 3DC6 (or 9013) with a β value greater than 100 to form a composite transistor. The schematic circuit diagram is shown in Figure 2. Utilize the amplification effect of the composite transistor to amplify the charging current of the measured capacitor, so as to increase the swing amplitude of the multimeter's pointer. Connect the measured capacitor between the base b and the collector c of the composite transistor, and connect the red and black test leads of the multimeter to the emitter e and the collector c of the composite transistor respectively.
If the pointer of the multimeter swings slightly and then returns to infinity, it indicates that the capacitor is normal.
If the pointer does not move or cannot return to infinity, it indicates that the capacitor is damaged.
During the testing operation, especially when measuring capacitors with a smaller capacitance, repeatedly swap the two contact points of the pins of the measured capacitor to clearly observe the swing of the multimeter's pointer.
