How to measure the quality of capacitors with pointer multimeter
When a capacitor with good performance is turned on, the needle of the multimeter should have a large swing;
The larger the capacitance of the capacitor, the larger the swing of the hands of the watch. After the swing, the hands of the watch can gradually return to zero.
If the pointer of the multimeter does not swing when the capacitor is powered on, it means that the capacitor is invalid or open circuit;
If the needle keeps indicating the power supply voltage without swinging, it means that the capacitor has been broken down and short-circuited;
If the hands of the watch swing normally but do not return to the zero position, it means that the capacitor has leakage. The higher the indicated voltage value, the greater the leakage.
It should be pointed out that the auxiliary DC voltage used for measuring capacitors with small capacity cannot exceed the withstand voltage of the capacitor under test, so as to avoid breakdown and damage of the capacitor due to the measurement. To accurately measure the capacitance of a capacitor, a capacitance bridge or a Q meter is required.
The above-mentioned simple detection method can only roughly judge the quality of the pressure gauge capacitor.
In the absence of special instruments, the quality and quality of capacitors can be detected and judged with the resistance file of a multimeter.
For fixed capacitors with large capacity (above 1μF), you can measure the two electrodes of the capacitor with the resistance gear (R×1000) of the multimeter. The needle should swing to the direction of small resistance, and then slowly swing back to around ∞.
Then exchange the test rod and try again, see the swing of the hands, the larger the swing, the larger the capacitance of the capacitor.
If the test rod touches the lead wire of the capacitor all the time, the pointer should be near ∞, otherwise, it indicates that the capacitor has electric leakage. The smaller the resistance value, the larger the leakage, and the quality of the capacitor is poor;
If the hands of the watch do not move at all during the measurement, it means that the capacitor has failed or is broken; if the hands of the watch swing but cannot return to the starting point, it means that the capacitor has a large leakage and its quality is not good.
For a capacitor with a small capacity, the pressure gauge often does not see the swing of the needle when measuring with a multimeter. At this time, you can use an external DC voltage and measure with the DC voltage range of the multimeter, and adjust the multimeter to the corresponding DC voltage range. Negative ( The black) test stick is connected to the negative pole of the DC power supply, the positive (red) test stick is connected to one end of the capacitor under test, and the other end is connected to the positive pole of the power supply.
How to measure the quality of capacitors with pointer multimeter
1. Use the multimeter resistance file to check whether the electrolytic capacitor is good or bad
The two leads of an electrolytic capacitor are divided into positive and negative. When checking whether it is good or bad, for an electrolytic capacitor with a lower withstand voltage (6V or 10V), the resistance file should be placed in the R×100 or R×1K file. Connect the red test lead to the negative terminal of the capacitor, and the black test lead to the positive terminal. At this time, the pointer of the multimeter will swing, and then return to zero or near zero. 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 the electrolytic capacitor
For some electrolytic capacitors with low withstand voltage, if the positive and negative leads are unclear, it can be judged according to its characteristics of small leakage current (large resistance value) when it is connected positively, and large leakage current when connected reversely. The specific method is: touch the two leads of the capacitor with red and black test leads, remember the size of the leakage current (resistance value) (the resistance value indicated when the pointer swings back and stops), and then short the positive and negative leads of the capacitor. Then, swap the red and black test leads and then measure the leakage current. Judgment is based on the indication value of the small leakage current, and the lead wire in contact with the black test lead is the positive terminal of the electrolytic capacitor. This method is more difficult to distinguish the polarity of electrolytic capacitors with small leakage current.
3. Check the variable capacitor with a multimeter
A variable capacitor has a set of fixed pieces and a set of moving pieces. Use the resistance gear of a multimeter to check whether there is any contact between the moving and fixed pieces. Connect the moving piece and the fixed piece with red and black test leads respectively, rotate the shaft handle, and the pointer of the ammeter does not move, indicating that there is no short circuit between the moving and fixed pieces ( touch piece); if the pointer swings, it means that there is a short circuit in the capacitor.
4. Use the multimeter resistance file to roughly identify the quality of capacitors with a capacity above 5000PF
The quality of capacitors above 5000PF can be roughly identified by using the resistance file of a multimeter (those below 5000PF can only judge whether the inside of the capacitor is broken down). When checking, set the resistance range to the high-end value of the range, and the two test leads are respectively in contact with the two ends of the capacitor. At this time, the pointer swings quickly and then recovers, and connects in reverse. The amplitude of the swing is larger than the first time, and then recovers. Such capacitors are good.
The larger the capacity of the capacitor, the greater the swing of the pointer of the ammeter during measurement, and the longer the recovery time of the pointer. We can compare the capacities of the two capacitors according to the swing of the pointer of the ammeter.
