Measuring method of measuring capacitance with digital multimeter
It is convenient to measure the quality of a capacitor by using the capacitance file of a digital multimeter. The following describes the specific measurement methods.
An electrolytic capacitor of 47μF, the capacity of which is measured by a digital multimeter, is shown as 45.17 μ f.
The method of judging the quality of capacitance
Adjust the range switch of the digital multimeter to the appropriate range of the capacitor file, and then insert the red and black probes of the multimeter into Cx jack and COM jack of the multimeter respectively (for the convenience of taking photos, the test wire with alligator clip is used instead of the probe), and then the red and black probes respectively touch the two pins of the capacitor (if the electrolytic capacitor is measured, it can be of no polarity). At this time, if the value displayed by the multimeter is close to the nominal value of the capacitor (generally, the error is allowed to be 5% ~ 10%), then.
For the capacitor damaged by breakdown, the resistance between its two pins is very small. At this time, the meter will display "1", that is, overflow. Therefore, when measuring the capacitor, if the position of the range switch of the multimeter is not wrong, but the meter displays "1", it means that the capacitor is likely to be damaged by breakdown or the leakage is too large (at this time, the resistance of the multimeter can be measured to confirm whether it is damaged).
For electrolytic capacitors placed for a long time, the electrolyte in some capacitors will gradually dry up, making their capacity very small. Therefore, when measuring electrolytic capacitors, if the displayed capacity is significantly lower than their nominal values, the capacitors are generally not suitable for use. The above picture shows a 100μF electrolytic capacitor that has been in use for several years, and its measured capacity is only 54.08 μ f.
The multimeter can be used to distinguish the quality of the capacitor, and three methods can be provided for your reference. The capacitor needs to be discharged before measurement, so it will not be repeated in the following.
1. Direct measurement
If the measured capacitance is less than the maximum range of the multimeter, it can be directly measured by the multimeter. If the capacitance is normal, the corresponding capacitance will be displayed on the display screen of the multimeter. The measured capacitance can be compared with the marked capacitance. If the two are equal or close, it can be determined that the capacitance is good.
2, diode file measurement
If the capacitance to be distinguished has exceeded the range of the multimeter, it is necessary to use the diode gear of the multimeter at this time, and also connect the probes to the two ends of the capacitor. If you see that the number is increasing on the dial, and the larger the capacitance, the more obvious this phenomenon is, so you can conclude that the measured capacitance is also good.
3, resistance measurement
This method is very similar to the second method. It can be selected when the capacitance exceeds the range of the multimeter. First, turn the watch hand to the resistance position, and then connect the watch hand to the two ends of the capacitor. If you can see that the number is increasing on the dial of the multimeter, the larger the capacitance, the slower the increase, so you can judge that the capacitor is good. If the number 1 is always displayed on the dial, then the capacitor is broken.
