Measurement of good and bad capacitors and their leakage current with a digital multimeter
Capacitors generally have three kinds of faults: breakdown damage, leakage current, and value change. Want to judge the machine equipment above the capacitance of good and bad, with a digital multimeter measurement can judge its good and bad. The following electrician introduces the method of measuring capacitance and leakage current with digital multimeter.
1, according to the capacitance to determine the capacitance of good and bad
Measure the capacitance with a digital multimeter.
Now many digital multimeter are with capacitance file, can directly measure the capacity, want to judge a capacitor good or bad, directly with a digital multimeter capacitance file to measure its capacity to know the capacitance of good or bad. Measurement, as shown in the figure above will be the multimeter range switch to the appropriate capacitance gear (for automatic range change multimeter do not need to select the gear), with the red and black pens were in contact with the capacitance of the two pins (for electrolytic capacitors, the measurement does not take into account the polarity of the pins), the multimeter shows the readings that is the capacitance. If the measured capacity is very close to its nominal value, the capacitor is good. Conversely, if the reading deviates significantly from the nominal value, the capacitor is problematic.
If the measured capacitance is significantly less than the nominal value, the capacitor is bad. General electrolytic capacitors placed for a long time, the internal electrolyte drying will lead to its capacity becomes very small, this capacitor is generally not suitable for use. If the actual measurement of a capacitor, the multimeter display reads "1", that is, overflow, this time you can use the multimeter resistance file to measure the resistance value, if the resistance value shown is very small, indicating that the capacitor has been damaged by breakdown. If the measured capacity of a capacitor is much larger than the nominal value, the capacitor has a large leakage current, generally this capacitor should not be used.
2, capacitance leakage current measurement
Capacitor leakage current measurement method.
For electrolytic capacitors placed for a long time, some insulation properties will be reduced, so that the leakage current becomes large, such leakage current of capacitors if the capacitance file with capacitance measurements of its capacity, the display capacity will be larger, at this time, we can measure the capacitance of the leakage current, to further determine whether it is available.
Measurement of leakage current, the measured capacitance series into a DC ammeter (can be measured with a digital multimeter 20mA file), and then connected with a 5V DC power supply, at first the ammeter shows the current is larger, and then gradually reduced until it tends to 0. Assuming that the capacitance is full of electricity, the ammeter shows that the current is not 0, indicating that the capacitance is leaking, and the current shown by the multimeter at this time is the leakage current of the capacitor.
