Digital multimeter measuring capacitance good or bad measuring method
A 47μF electrolytic capacitor, measured its capacity with the capacitance gear of a digital multimeter, shows 45.17μF.
Judge the capacitor good or bad method
Adjust the range switch of digital multimeter to the appropriate range of capacitance, and then insert the red and black pens of multimeter into the Cx jack and COM jack of multimeter respectively (for the convenience of taking pictures, the test line with alligator clips is used instead of pens), and then the red and black pens are contacted with the two pins of capacitance respectively (if it is to measure the electrolytic capacitance, it can be regardless of the polarity), and then the multimeter will show the value if it is close to the nominal value of capacitance (generally allowed to have 5% to 10%). Close to the value displayed by the multimeter and the nominal value of the capacitor (generally allow a 5% to 10% error), it is said that the capacitor is good.
Multimeter capacitance file measurement of a 47μF electrolytic capacitor, the actual display capacity of 45.17μF, the error in the specified range, indicating that the capacitor is good.
Multimeter capacitance gear measurement of a nominal value of 0.1μF/630V good CBB capacitor, the actual display capacity of 0.1037μF.
For the breakdown of damaged capacitors, the resistance between the two pins is very small, at this time with the multimeter capacitance file measurement, the meter will display "1", that is, overflow, so in the measurement of capacitance, if the multimeter range switch position is not dialled wrongly, but the meter displays "1", then This means that the capacitor is likely to be damaged or leakage is too large (at this time, the resistance of the multimeter can be used to measure the resistance value, to confirm whether the damage).
For a long time placed in the electrolytic capacitor, some capacitors will gradually dry up the internal electrolyte, so that its capacity becomes very small, so in the measurement of electrolytic capacitors, if the displayed capacity is significantly lower than its nominal value, the capacitor is generally not suitable for use. The figure above shows a put a few years of 100μF electrolytic capacitors, measured capacity of only 54.08μF.
Identify capacitors good or bad can use a multimeter, can provide three methods for your reference, in the measurement of the capacitor needs to be discharged before, in the following will not be repeated.
1, direct measurement
If the measured capacitance size is less than the maximum range of the multimeter can use the multimeter to measure directly, if the capacitance is normal will show the corresponding capacity size on the display of the multimeter, the measured capacitance size can be compared with the size of the marked capacitance, if the two are equal or closer, you can determine that the capacitance is good.
2, diode file measurement
If the size of the capacitance to be identified has exceeded the range of the multimeter, it is necessary to use the diode file of the multimeter, the same pen connected to both ends of the capacitor, if you see on the dial the number in the increasing, and capacitance of the phenomenon of the larger the more obvious, then it can be determined that the measured capacitance is also good.
3, resistance measurement
This method and the second method is very similar, can be used in the capacitance capacity beyond the range of the multimeter, first of all, the needle rotated to the resistance file, and then the needle connected to both ends of the capacitor, if the dial in the multimeter can see the number in the increasing capacitance increases the slower the increase, then you can judge the capacitance is good, if the dial is always displaying the number of 1, then this capacitor is bad.
