How to Detect Capacitors with a Multimeter
1. Detection of fixed capacitors
(1) For the detection of fixed capacitors with a capacity above 0.01 pF, adjust the pointer multimeter to the R × 10k ohm range and perform ohm zeroing. Then, use the red and black probes of the multimeter to touch the two pins of the capacitor and observe the changes in the multimeter pointer, as shown in Figure 1. If at the moment when the probe is connected, the pointer of the multimeter swings slightly to the right and then returns to infinity, and after replacing the probe and measuring again, the pointer also swings to the right and returns to infinity, it can be determined that the capacitor is normal; If the pointer of the multimeter swings to around "0" at the moment when the probe is connected, it can be determined that the capacitor has been broken down or severely leaked; If at the moment the probe is connected, the pointer no longer returns to infinity after swinging, it can be determined that the capacitor is leaking electricity; If the multimeter pointer does not swing twice, it can be determined that the capacitor is open circuit.
(2) When detecting fixed capacitors with a capacity of less than 0.01 pF and small capacitors below 10 pF, a multimeter is used for measurement due to the small capacitance. Only leakage, internal short circuit, or breakdown can be checked. When measuring, use the R × 10k range of the multimeter and connect the two probes to either pin of the capacitor. The resistance value should be infinite. If the resistance value is zero, it can be determined that the capacitor is damaged due to leakage or internal breakdown.
(3) Detect 10pF~0.01; The tF fixed capacitor can be fixed using the following method. Set the multimeter to the R × 10k range and select two transistors 3DC6 (or 9013) with a delta value greater than 100 to form a composite transistor. The circuit schematic is shown in Figure 2. By utilizing the amplification effect of the composite tube, the charging current of the measured capacitor is amplified to increase the swing amplitude of the multimeter pointer. Connect the tested capacitor between the base b and collector c of the composite tube, and connect the red and black probes of the multimeter to the emitter e and collector c of the composite tube, respectively. If the pointer of the multimeter swings slightly and returns to infinity, it indicates that the capacitance is normal; If the pointer does not move or cannot return to infinity, it indicates that the capacitor is damaged. During testing operations, especially when measuring small capacity capacitors, it is necessary to repeatedly switch the two contact points of the tested capacitor pins to clearly see the swing of the multimeter pointer.
