How to test if the capacitor is damaged with a universal meter

There are 3 cases when a capacitor is broken:1Leakage, 2Breakdown, 3No capacity. The measurement requires a suitable range range:

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 10pf fixed capacitors.

To detect whether the fixed capacitor of 10pf is charged, and then judge its quality or bad, the multimeter can choose R 1K block, the value of the two transistors is more than 100, 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. Detect the above fixed capacitance.

To detect the above fixed capacitance, you can use the R 10K block of the multimeter to directly test whether the capacitor has a charging process and whether there is an internal short circuit or leakage, and the capacitor capacity can be estimated according to the amplitude of the pointer swinging to the right.

How to measure the quality of capacitance with a universal meter.

Detection Method:

1. The open circuit is very easy to judge, that is, there is no charging and discharging process, but for small capacity capacitors, because the charging and discharging are not obvious, it is best to test the capacitor file.

2. If it is a digital multimeter, then the red watch pen is connected to the positive pole of the capacitor, if it is a pointer multimeter, it is the positive pole of the black watch pen connected to the capacitor, because the capacity is relatively large, so there is a charging process, and the resistance value will have a gradual increase process. In this process, until the resistance value is stable. The electrolytic capacitor with low withstand voltage and large capacity has a resistance value after stabilization, which can be regarded as the leakage value.

3. The resistance at both ends of the capacitor is close to zero, which can be regarded as a short circuit.

4. When there is no multimeter with capacitance file, or when the range of capacitance file is not enough, it is impossible to measure the value of capacitance. You can use a good capacitor, when measuring, look at the pointer, or the minimum value of the value, to compare and confirm the quality of the capacitance. When measuring, pay attention to the capacitance to be fully discharged before measurement.

Digital multimeters (including pointer universal meters) can generally only measure capacitors with large capacitance (because of the large capacity, there is a more obvious charging process).

First, short circuit the two pins of the capacitor to release its possible power storage. When the capacitor is first connected, the number of resistors of a certain size will be displayed on the digital meter because the capacitor will be charged, and it will continue to beat, and the data will continue to increase in the runout until infinity is displayed. The data is increasing at a rate that reflects the size of the capacitor.

The larger the capacitor, the longer it takes to show infinity.

When the capacitor is large enough and there is no charging process, the capacitor fails. If infinity is not shown at the end of charging, it is a leakage of the capacitor.

Note that the charging process of capacitors is too short to be visible.

There are already digital universal meters that can measure the capacitance of capacitors, such as the 890C.

How does a multimeter measure the capacity of a capacitor and judge the quality of the capacitor?

Aim the red probe of the multimeter at the negative pole of the capacitor and the black probe at the positive pole of the capacitor, and then look at the change of the pointer. If the multimeter pointer is biased to the left, the capacitance data is normal. The magnitude of the capacitance can also be estimated based on the amplitude of the pointer shift.

If the pointer is shifted to the right, or to the "0" position, the capacitor is damaged and the measurement is inaccurate.

1. To judge the polarity, first adjust the multimeter to 100 or 1k ohms, assume that one pole is positive, let the black watch pen connect with it, and the red watch pen connect with the other pole, write down the resistance value, and then discharge the capacitor, that is, let the two poles contact, and then change the meter pen to measure the resistance, and the black watch pen with a large resistance value is connected to the positive pole of the capacitor.

2. Adjust the multimeter to the appropriate gear in ohms, and the principle of gear selection is: 20k gear for 1 F capacitor, 2K gear for 1 100 F capacitor, and 200 gear for more than 100 and F.

3. Then use the red pen of the multimeter to connect the positive pole of the capacitor, and the black pen to connect the negative pole of the capacitor, if the display increases slowly from 0, and finally displays the overflow symbol 1, the capacitance is normal, if it is always displayed as 0, the capacitor is short-circuited internally, and if it is always displayed 1, the capacitor is open internally.

Since the capacitor has a charging characteristic, it is sufficient to use a resistor position.

First, adjust the resistance to the highest setting, observe the value, if the capacitor is broken, that is, the capacitor breaks down and is short-circuited, the resistance should be displayed as 0 ohms. If it's not bad, it should be from a numerical value to infinity.

The number of digits displayed in a DMM is usually 31 2 digits 81 2 digits. There are two principles for determining the number of digits displayed in a digital instrument: one is that the number of digits that can display all digits from 0 9 is an integer number;

The second is that the numerical value of the fractional digit is the highest digit of the maximum display value as the numerator, and the counting value is 2000 when using the full scale, which indicates that the meter has 3 integer digits, and the numerator of the fractional digit is 1, and the denominator is 2, so it is called 31 2 digits, which is read as "three and a half digits", and its highest digit can only display 0 or 1 (0 is usually not displayed).

32 The highest digit of a 3-digit (pronounced "three and two-thirds") digital multimeter can only display a number of 0 2, so the maximum display value is 2999. In the same case, it is 50% higher than the 31 2-digit digital multimeter, especially when measuring 380V AC voltage.