Capacitors are both the most common electrical components. It is also an easily damaged electrical component. To detect the quality of a capacitor without special instrumentation, the following methods are available:
1, multimeter detection method
For fixed capacitors above O.01μF. The R×1k 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 amplitude of the pointer swinging to the right. When testing, first touch the two pins of the capacitor with two meter pens, then change the test pen and touch it again. If the capacitor is good, the multimeter pointer will swing to the right and then quickly return to the infinity position to the left. The larger the capacitance, the greater the swing of the pointer. If the two fingers of the capacitor are touched repeatedly, the pointer of the multimeter will not swing to the right, indicating that the capacity of the capacitor has been less than 0.01μF or has disappeared. During the measurement, if the pointer swings to the right, it can no longer return to the infinity position to the left, indicating that the capacitor is leaking or has broken down.
2, fuse simple detection method
Use a fuse (the rated current In of the fuse is determined by: IN = 0.8 / C (A), where C is the capacitance of the capacitor) and the capacitor to be tested is connected in series to the 220V AC power supply, if the fuse The fuse is broken, indicating that the capacitor has been short-circuited inside. If the fuse of the fuse does not break, after a few seconds of charging, cut off the power supply, and use a screwdriver with an insulating handle to short-circuit the two poles of the capacitor. A spark occurs and the capacitor is good. Conversely, it indicates that the capacitance of the capacitor has become smaller or has been opened. Use this method to judge whether the capacitor is good or bad should be repeated several times to get the correct conclusion.
3, incandescent bulb and capacitor series detection method
Connect the incandescent bulb and capacitor in series with the 220V AC power supply. If the brightness of the incandescent bulb is darker than connecting it directly to the 220V AC power supply, the capacitor is good. If the incandescent bulb is not lit, the inside of the capacitor to be tested is indicated. The circuit has been disconnected; if the brightness of the incandescent bulb is the same as the brightness of the direct connection to the 220V AC power supply, the internals of the capacitor have been shorted.
4, megohmmeter detection method
It can also be detected with a megohmmeter (250V class). Shake the handle, such as the pointer is at infinity, indicating that the capacitor is internally open; if the pointer is at zero, it indicates that the capacitor is internally shorted. It can also be used as a ground test for capacitors by connecting the terminals of the megohmmeter to the terminals and housing of the capacitor. Shake the handle, such as the pointer at zero, indicating the internal ground of the capacitor.
5, the measurement of capacitor capacitance
The capacity of the power capacitor can be measured with a multimeter without a dedicated meter. The specific method is: using a fuse (the specification is determined by the capacitance of the capacitor) and the capacitor to be tested are connected in series to the 220V AC power supply. Use the multimeter's AC voltage file to measure the voltage across the capacitor, U(V).
The current I (mA) through the capacitor is measured with the multimeter's AC current file. Since I=U/XC and XC=1/(2πfC), where f is the frequency of the alternating current. Therefore, the capacitance of the capacitor CC = 3.18 × (I / U) (micro method).
