Detection method of fixed capacitor

1. Detect small capacitors below 10pF: Because the capacity of fixed capacitors below 10pF is too small, using a multimeter to measure can only qualitatively check whether there is leakage, internal short circuit or breakdown. When measuring, you can use the multimeter R×10k block, and use two test pens to connect the two pins of the capacitor at will, and the resistance value should be infinite. If the measured resistance value (the pointer swings to the right) is zero, it means that the capacitor is damaged by leakage or internal breakdown.

2. Detect 10PF～001μF fixed capacitors: by judging whether there is charging phenomenon, and then judge whether it is good or bad. The multimeter selects R×1k block. The β value of the two triodes is above 100, and the penetration current should be small. 3DG6 and other silicon triodes can be selected to form a composite tube. The red and black test leads of the multimeter are respectively connected to the emitter e and collector c of the composite tube. Due to the amplifying effect of the composite triode, the charging and discharging process of the capacitor under test is amplified, so that the pendulum of the multimeter pointer is increased, which is convenient for observation.

It should be noted that during the test operation, especially when measuring small-capacity capacitors, it is necessary to repeatedly exchange the pins of the capacitor under test to contact points A and B, in order to clearly see the swing of the multimeter pointer. For fixed capacitors above 001μF, the R×10k block of the multimeter can be used to directly test whether the capacitor has a charging process and whether there is an internal short circuit or leakage, and the capacity of the capacitor can be estimated according to the amplitude of the pointer swinging to the right.