* Question
| Capacitor detection method and experience |
* Answer
| 1. 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, and only qualitatively check for leakage, internal short circuit or breakdown.The multimeter uses R × 1k block.The beta values of the two triodes are all above 100 and the penetration current is small.A composite tube of 3DG6 and other types of silicon triodes can be selected.The red and black test leads of the multimeter are respectively connected to the emitter e and the collector c of the composite tube.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.Because the capacity of electrolytic capacitors is much larger than that of general fixed capacitors, the appropriate range should be selected for different capacities when measuring.According to experience, under normal circumstances, the capacitance between 1 ~ 47μF can be measured by R × 1k block, and the capacitance larger than 47μF can be measured by R × 100 block.Practical experience shows that the leakage resistance of electrolytic capacitors should generally be several hundred kΩ or more, otherwise, it will not work properly.In the test, if there is no charging in the forward and reverse directions, that is, the hands are not moving, the capacity disappears or the internal circuit is broken; if the measured resistance is small or zero, the leakage of the capacitor is large or the breakdown is broken.Can no longer be used.? Using the multimeter electric block, using the method of positive and negative charging of the electrolytic capacitor, according to the magnitude of the swing of the pointer to the right, the capacity of the electrolytic capacitor can be estimated.
3, the detection of variable capacitor A gently rotate the shaft by hand, should feel very smooth, should not feel sometimes loose or even stuck.Place the multimeter in the R×10k block. Connect one of the two test leads to the output of the variable capacitor and the lead of the fixed piece with one hand. The other hand will slowly rotate the rotating shaft several times. The multimeter pointer should beInfinity position does not move. |
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