A capacitor is a device that holds a charge and is one of a large number of electronic components used in electronic devices. Any two conductors (including wires) that are insulated from each other and closely spaced each other constitute a capacitor. Widely used in the circuit of the block-through, coupling, bypass, filtering, tuning loop, energy conversion, control, etc., then Xiaobian and share the measurement method of capacitors.
Capacitor
Capacitor characteristics
It has charge and discharge characteristics and the ability to block the passage of DC current, allowing AC current to pass.
During charging and discharging, the charge on the plates is accumulated, that is, the voltage is established, so the voltage on the capacitor cannot be abrupt.
Capacitor Charging: The two plates are each charged with an equal amount of different charges. The absolute value of the charge of each plate is called the charge of the capacitor.
Discharge of the capacitor: The positive and negative charges of the two poles of the capacitor are neutralized by the wires. A short current is generated on the wire during discharge.
The capacitive reactance of a capacitor is inversely proportional to the frequency and capacity. That is, when analyzing the magnitude of the capacitive reactance, it is necessary to contact the frequency of the signal and the size of the capacity.
Capacitor measurement method
Detected when disconnected from the line.
Use the multimeter R × 1k block, before the detection, first touch the two pins of the electrolytic capacitor to discharge the residual charge in the capacitor. When the test chart is just turned on, the hands are deflected to the right by an angle, then the hands are slowly Turn left and the last hand stops. The resistance indicated by the stop of the hand is the leakage resistance of the capacitor. The larger the resistance, the better, it should be close to infinity. If the leakage resistance is only a few tens of kiloohms, this electrolytic capacitor is seriously leaky. The greater the angle at which the hands swing to the right (the hands should also swing back to the left), indicating that the capacitance of this electrolytic capacitor is also larger, and conversely, the smaller the capacity.
Direct detection on the line.
It is mainly to detect whether the capacitor has been opened or has penetrated two significant problems, and the leakage problem is generally unacceptable due to the influence of the external circuit. Use the multimeter R × 1 block, after the circuit is disconnected, first discharge the charge remaining in the capacitor. If the hands are deflected to the right during measurement, the internal electrolytic circuit is broken. If the resistance indicated by the hand is deflected to the right is small (close to short circuit), the capacitor is seriously leaking or has broken down. If the hands are not turned back to the right, but the indicated resistance is not small, it indicates that the capacitor may be open, and should be further tested after disconnecting the circuit.
Detected when the line is powered.
If it is suspected that the electrolytic capacitor only has a breakdown problem under the energized state, the circuit can be energized, and then the DC voltage across the capacitor is measured with a multimeter DC gear. If the voltage is very low or 0V, the capacitor has broken down. If the positive and negative signs of the electrolytic capacitor are unclear, the positive and negative poles must be identified first. The test is changed twice for the multimeter, and the leakage is large (the resistance is small), the black pen is connected to the negative pole and the other is the positive pole.
