How to check the quality of the capacitor, how to check the quality of the capacitor?

1. Detect small capacitance below 10pf.

Because the capacitance of fixed capacitors below 10pf is too small, it can only be qualitatively checked for leakage, internal short circuit or breakdown by measuring with a multimeter. When measuring, you can choose to use the multimeter R 10K block, and use the two meter pens to connect the two pins of the capacitor at will, and the resistance value should be infinity. If the measured resistance (the needle swings to the right) is zero, it means that the capacitor is damaged by leakage or internal breakdown.

2. Detect whether the 10pf fixed capacitor is charged, and then judge its quality. The multimeter uses R 1K gear. Both transistors have a value of 100 or more, and the penetration current should be small.

3DG6 and other types of silicon transistors can be selected to form composite tubes. The red and black pencils of the multimeter are connected to the emitter E and collector C of the composite tube, respectively. Due to the amplification effect of the composite transistor, the charging and discharging process of the measured capacitor is amplified, so that the swing amplitude of the multimeter pointer is increased, so as to facilitate observation.

It should be noted that during the test operation, especially when measuring the capacitance of a smaller capacitance, it is necessary to repeatedly switch the pins of the capacitor under test to contact the two points A and B, so that the swing of the multimeter pointer can be clearly seen.

3. For the above fixed capacitors, the R 10K 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 amplitude of the pointer swinging to the right.

It is best to measure with a capacitance meter. First, look at how the nominal value of the capacitance and the capacity you actually measure change. If it is within the prescribed range, it can be considered good.

If it is less than the error range of the nominal value, the capacitance is insufficient, and it can be used in general situations (such as power supply filter circuits).If it is greater than the margin of error of the nominal value. Indicates that there is leakage at this point.

The larger the capacity, the more serious the leakage. It needs to be replaced.

In general, the capacitors sold in the market (especially electrolytic capacitors) have a majority of downward deviations. So once you find that the capacity is too large, don't use it.

You hit the multimeter (pointer type) to RX1K after calibrating the meter, and then short the capacitor and then separate, the meter hand is connected to the two pins, if the deflection and return to infinity, then change the watch hand and test again, if it is still deflected and return to infinity, then the capacitance (electrolytic capacitor) is good, if it is a non-polar capacitor, you need to use RX10K gear.

The easiest way is to test the capacitor discharge, if a good capacitor can discharge, the bad capacitor will not discharge.

Just use a multimeter to detect the resistance.

Measurements can be made directly with a digital meter.

1) Leakage discrimination of fixed capacitors:

Use the resistance range file " " of the multimeter

Capacity 1 F or more with R 1k gear.

5000pf capacity 1 f with r 10 gears.

When the watch rod touches the poles of the capacitor, the meter head needle should first jump in the clockwise direction, and then gradually recover counterclockwise, that is, retreat to r=. If it cannot be restored, the stable reading indicates the resistance value of the capacitor leakage.

2) Identification of capacitor capacity: (rough measurement).

When touching both ends of the capacitor with the watch rod, the meter head needle should jump up and then gradually recover. After the black and red sticks are reversed, the needle jumps and jumps higher, and then gradually recovers. This is the case of capacitor charge and discharge.

The larger the capacitance of the capacitor, the greater the meter head pointer runout. The pointer also recovers more slowly. The size of the pointer can be determined by the height of its jumping.

For capacitors with small capacitance below 50,000pf, the charging and discharging phenomenon can no longer be seen with the highest resistance level of the multimeter, and a special measuring instrument should be used to distinguish it.

Usually, the quality of the capacitor, the meter can only check whether there is leakage between the capacitor plates, whether it can withstand the rated voltage, that is, whether it can still be counted as a "capacitor" under the rated voltage, or whether the capacitor has a large change in capacitance.

As for the actual capacitance of this capacitor, especially the capacitor with a small capacitance, the current inspection method should use a "bridge", or a special meter (usually an internal meter based on the "bridge") to measure its capacitance.

Methods to detect the quality of capacitance:

Method 1: Pointer multimeter measurement.

1. Check the quality of the electrolytic capacitor with the resistance file of the multimeter.

The two leads of the electrolytic capacitor are positive and negative, when checking its quality, for the electrolytic capacitor with low withstand voltage (6V or L0V), the resistance gear should be placed in the R 100 or R 1K gear, and the red watch pen should be connected to the negative end of the capacitor, and the black watch pen should be connected to the positive end, then the multimeter pointer will swing, and then return to the zero position or near the zero position. Such electrolytic capacitors are good. The larger the capacity of the electrolytic capacitor, the longer the charging time and the slower the pointer swings.

2. Use a multimeter to judge the positive and negative leads of electrolytic capacitors Some electrolytic capacitors with low withstand voltage, if the positive and negative leads are not clearly marked, they can be judged according to the characteristics of small leakage current (large resistance value) when it is connected positively and large leakage current when it is reversed. The specific method is to touch the two leads of the capacitor with a red and black watch pen, remember the size of the leakage current (resistance value) (the resistance value indicated when the pointer swings back and stops), and then shorts the positive and negative leads of the capacitor, and then measures the leakage current after the red and black watch pens are reversed.

The indication of the low leakage current is used as a criterion, and the lead that comes into contact with the black stylus is the positive end of the electrolytic capacitor. This method makes it difficult to distinguish the polarity of electrolytic capacitors with low leakage current.

3. Check the variable capacitor with a multimeter The variable capacitor has a set of fixed pieces and a group of moving pieces. Use the multimeter resistance file to check whether there is a touch between the moving and fixed pieces, use the red and black watch pens to connect the moving piece and the fixed piece respectively, rotate the shaft handle, and the meter pointer does not move, indicating that there is no short circuit (touching the piece) between the moving and fixed pieces; If the pointer wiggles, it means that the capacitor has a short circuit.

4. Use the resistance file of the multimeter to roughly identify the quality of capacitors with capacitance above 5000pf.

The multimeter resistance level can roughly identify the quality of capacitors above 5000pf (those below 5000pf can only judge whether the capacitor is broken down). When checking, put the resistance range at the high end of the range, and the two meter pens are in contact with the two ends of the capacitor, then the pointer quickly swings and then recovers, reverses the connection, the swing amplitude is greater than the first time, and then recovers. Such capacitors are good.

How to detect if the capacitor is broken.

Here's how to measure the quality of capacitance:

1. Multimeter detection method:

For the above fixed capacitors. The capacitor can be directly tested with the R 1k stop of the multimeter for the charging process and whether there is an internal short circuit or leakage, and the capacitance of the capacitor can be estimated based on the amplitude of the pointer swinging to the right.

When testing the operation, first touch the two pins of the capacitor with two meter pens, and then change the meter pen to touch it again, if the capacitance is good, the multimeter pointer will swing to the right, and then quickly return to the infinity position to the left. The greater the capacitance, the greater the swing of the pointer.

If the multimeter needle does not swing to the right after repeatedly changing the meter pen and touching the two pins of the capacitor, the capacitance of the capacitor has been reduced or has disappeared. During the measurement, if the pointer swings to the right and cannot return to the infinity position to the left, it means that the capacitor has leaked or has broken down.

2. Simple fuse detection method:

The fuse (the rated current of the fuse in is determined by the following formula: in=, where c is the capacitance of the capacitor) and the capacitor to be detected are connected in series on the AC power supply of 220V, if the fuse of the fuse bursts, it means that the capacitor has been short-circuited inside.

If the fuse of the fuse does not burst, 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 to discharge, and if there is a spark, the capacitor is good. Conversely, it means that the capacitance of the capacitor has become smaller or has been opened. Judging the quality of capacitors with this method should be repeated several times to get the correct conclusion.

3. Incandescent bulb and capacitor series detection method:

Connect the incandescent bulb and the capacitor in series to 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 up, it means that the inside of the capacitor to be tested has been disconnected; If the brightness of an incandescent bulb is the same as the brightness of the bulb that is connected directly to the 220V AC power supply, the inside of the capacitor has been shorted.

How to judge the quality of the capacitance:

1. It can be connected to AC power for detection.

Connect it with 220V AC, connect one pole first, touch the other capacitor with another power cord, if there is an obvious small spark, you can be sure that this capacitor is charged and not damaged.

2. Use the capacitance measurement file of an analog multimeter or digital meter.

Use a pointer multimeter or digital meter to measure the capacitance stop, connect the meter to the two poles of the capacitor, the multimeter pointer swings, slowly move to near zero to indicate that it is good, the larger the capacitor capacity, the longer the charging time will be, the slower the pointer swings to the zero direction, after connecting the meter, the pointer does not move, indicating that the capacitor is damaged.

3. Use a digital multimeter to detect.

Dial the DMM to the appropriate resistor, and then touch the two poles of the capacitor respectively, the display value will gradually increase from 0, if the display value is always 0, it means that the capacitor is short-circuited.

4. Multimeter capacitance block measurement.

Use a multimeter to measure, first adjust the function switch to 20uf or 200uf, and measure the capacitance poles in the middle two holes, and then the capacitance will be displayed. In addition, the capacitor has been used, remember to discharge it before measuring.