Detection method of fixed capacitor.
1. Detect small capacitance below 10pF: Because the capacitance of the fixed capacitor below 10pF is too small, it can only be checked qualitatively if there is leakage, internal short circuit or breakdown phenomenon by using a multimeter to measure it. When measuring, you can choose the R×10k block of the multimeter, and use the two test leads to connect the two pins of the capacitor arbitrarily, and the resistance 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 a charging phenomenon, and then judge whether it is good or bad. The multimeter selects the R×1k block. The β values of the two triodes are both above 100, and the penetration current should be small. 3DG6 and other types of silicon transistors can be used to form composite tubes. 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 amplification effect of the composite triode, the charging and discharging process of the measured capacitor is amplified, and the pendulum of the pointer of the multimeter is increased, which is convenient for observation.
It should be noted that: During the test operation, especially when measuring a capacitor with a small capacity, it is necessary to repeatedly switch the pins of the capacitor under test to touch points A and B, so that the swing of the pointer of the multimeter can be clearly seen. For fixed capacitance 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 magnitude of the pointer swinging to the right.
