Capacitor Detection Tips Sharing (I)

Capacitor detection methods are mainly divided into three major categories: detection of variable capacitors, detection of electrolytic capacitors, and detection of fixed capacitors.

1. Detection of variable capacitors

A. Gently rotate the shaft by hand, it should feel very smooth, and should not feel sometimes loose or even stuck. When the axial direction of the load is pushed forward, backward, up, down, left, right, etc., the shaft should not be loose.

B. Rotate the shaft with one hand and gently touch the outer edge of the group with the other hand. There should be no looseness. The variable capacitor with poor contact between the rotating shaft and the moving piece can no longer be used.

C. Place the multimeter in the R×10k block, and connect the two test leads to the output end of the variable capacitor and the lead end of the fixed piece in one hand. The other hand will slowly rotate the rotating shaft several times back and forth, and the multimeter pointers are Should not move at infinity. In the process of rotating the shaft, if the pointer sometimes points to zero, it means there is a short circuit between the moving piece and the fixed piece; if it touches an angle, the multimeter reading is not infinite but a certain resistance value appears, indicating that the variable capacitor is moving. There is leakage between the film and the stator.

2. Detection of fixed capacitors

A. Detecting small capacitors below 10pF Because the fixed capacitor capacity below 10pF is too small, use a multimeter to measure, only qualitatively check for leakage, internal short circuit or breakdown. When measuring, you can use the multimeter R × 10k block, use two meter pens to connect the two pins of the capacitor, the resistance should be infinity. If the measured resistance value (the pointer swings to the right) is zero, the capacitor leakage is damaged or internal breakdown.

B. Detect whether the 10PF~0.01μF fixed capacitor has a charging phenomenon, and then judge whether it is good or bad. The multimeter uses R × 1k block. The beta values of the two triodes are all above 100, and the penetration current can be composed of a composite transistor such as a 3DG6 type silicon triode. The red and black test leads of the multimeter are respectively connected to the emitter e and the 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, so that the multimeter pointer swing amplitude is increased, thereby facilitating observation. It should be noted that during the test operation, especially when measuring the capacitance of a small capacity, it is necessary to repeatedly exchange the two points of the measured capacitor pins to contact A and B to clearly see the swing of the multimeter pointer.

C. For fixed capacitors above 0.01μF, use the R×10k block of the multimeter to directly test the capacitor for charging process and whether there is internal short circuit or leakage, and estimate the capacity of the capacitor according to the amplitude of the pointer swinging to the right.