Several Common and Simple Detection Methods for Capacitors

Capacitors are the most commonly used electrical components. It is also an electrical component that is easily damaged. In the absence of special instrumentation to detect the quality of the capacitor, it can be used in several ways:

1. Multimeter detection method

For O.01μF fixed capacitors. The multimeter's R×1k block can be used to directly test whether the capacitor is charged and whether there is an internal short circuit or leakage, and the capacity of the capacitor can be estimated based on the amplitude of the pointer swinging to the right. During the test operation, first touch the two pins of the capacitor with the two table pens, and then change the table pen to touch again. If the capacitor is good, the pointer of the multimeter will swing to the right and immediately return to the infinite position to the left. The larger the capacitance, the larger the pointer's swing. If you repeatedly change the test pen to touch the two pins of the capacitor, the pointer of the multimeter will not swing to the right at all, indicating that the capacity of the capacitor is less than 0.01μF or has disappeared. During the measurement, if the pointer swings to the right, it cannot return to the infinite position again, indicating that the capacitor is leaking or has broken down.

2. Fuse simple detection method

Use a fuse whose rated current In is determined by the following equation: IN = 0.8/C(A) where C is the capacitance of the capacitor and the capacitor to be tested is connected in series with a 220V AC power supply, if the fuse The rupture of the fuse indicates that the capacitor has been short-circuited. 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 insulated handle to short-circuit discharge of the two terminals of the capacitor. Sparks occur indicating that the capacitor is good. Conversely, it means that the capacitance of the capacitor has become smaller or it has been opened. Using this method to judge the capacitor is good or bad should be repeated several times to get the correct conclusion.

3. Incandescent bulbs and capacitors in series detection method

Connect the incandescent bulb and the capacitor in series with the 220V AC power supply. If the brightness of the incandescent bulb is darker than if it is directly connected to the 220V AC power supply, the capacitor is good; if the incandescent bulb does not light, it means the internal of the tested capacitor. Has been broken; if the brightness of the incandescent bulb and its direct connection to the brightness of the 220V AC power supply, indicating that the capacitor's internal short circuit.

4. Megohm detection method

Megohmmeter (250V class) can also be used for detection. Shake the handle. If the pointer points to infinity, it means that the capacitor is open circuited; if the pointer is at zero, it means that the capacitor has an internal short circuit. It is also possible to do a capacitor earth test by connecting the megohmmeter terminals to the capacitor terminals and the housing. Shake the handle. If the pointer is at zero, it indicates that the capacitor is open to the ground.

5. The measurement of capacitor capacitance

A multimeter can be used to measure the capacitance of a power capacitor without a dedicated meter. The specific method is to use a fuse (its size is determined by the capacitance of the capacitor) and the capacitor to be tested is connected in series to the 220V AC power supply. Measure the voltage U(V) across the capacitor using the multimeter's AC voltage profile.

Measure the current I (mA) through the capacitor using the multimeter's AC current profile. Because 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 x (I/U) (microfarad).