Capacitor detection skills (2)

Detection of fixed capacitors

A .Detection of small capacitors below 10pF because the capacity of fixed capacitors below 10pF is too small to be measured with a multimeter, it can only be qualitatively checked whether it has leakage, internal short circuit or breakdown phenomenon. In the measurement, the multimeter R × 10k block can be selected, and two pins of capacitance can be randomly connected with the two meter pens. The resistance value should be infinite. If the measured resistance (the pointer swinging to the right) is zero, then the capacitance leakage damage or internal breakdown.

B .Detects whether there is charging phenomenon in 10PFN 0.01 μ F fixed capacitor, and then judges whether it is good or bad. The multimeter uses R × 1k block. The β value of the two transistors is more than 100, and the penetration current can be selected as 3DG6 type silicon transistor composite transistor. Red and black meter pens of the multimeter are connected to the emitter e and the collector c of the composite tube, respectively. Because of the amplification effect of the compound transistor, the charge-discharge process of the measured capacitance is amplified, so that the amplitude of the pointer pendulum of the multimeter is increased, which is easy to be observed. It should be noted that in the test operation, especially in the measurement of the capacitance of smaller capacity, it is necessary to repeatedly change the capacitance pin to contact the A and B points in order to clearly see the swing of the multimeter pointer.

C .For fixed capacitors above 0.01 μ F, the R × 10k block of multimeter can be used to directly test whether the capacitor has charged process and whether there is an internal short circuit or leakage. The capacity of the capacitor can be estimated depending on the amplitude of the pointer swinging to the right.