Capacitance for Digital Multimeter Detection
The pointer multimeter can only detect the quality of the capacitor (the open circuit fault of the small-capacity capacitor should not be judged) and roughly estimate the size of the capacitor, but cannot accurately measure the size of the capacitor. The capacitance of the capacitor usually requires a capacitance meter, a digital multimeter and a dedicated Capacitance measuring instrument to measure. When using a digital multimeter to measure the capacitance of a capacitor, it should be noted that not all capacitors can be measured, and it should be determined according to the measurement gear of the digital multimeter. Some digital multimeters have multiple capacitance measurement gears, which can measure capacitance from 2nF to 2;tF, and some can measure capacitance from ⒛nF to ⒛0ctF, while some digital multimeters only have one capacitance measurement gear of ⒛0ptF. When using a digital multimeter to measure the capacitance of a capacitor, place the digital multimeter in the capacitance gear, select an appropriate gear according to the capacitance, and after the capacitor to be tested is fully discharged, insert the capacitor to be tested directly into the test hole or two test leads Measurements were made in direct contact, respectively. The display of the digital multimeter will directly display the capacity of the capacitor to be tested.
If the value displayed is equal to or very close to the nominal capacity, it means that the capacitor is normal; The measuring range of the multimeter can be replaced by a multimeter with an appropriate range. If the difference is still too large after the replacement of the multimeter, it means that the capacitor under test has deteriorated and cannot be used anymore; if the value displayed by the capacitor under test is much smaller than the nominal capacity, it means that the capacitor under test is damaged.
Note: (1) If the capacitance of the capacitor to be tested exceeds the measurement range of the multimeter, it cannot be measured with a digital multimeter.
(2) The connection method of the test lead of the digital multimeter is opposite to that of the pointer multimeter. The black test lead of the pointer multimeter is connected to the positive pole of the power supply inside the meter, which is the current outflow end of the meter; the red test lead of the digital multimeter is connected to the inside of the meter. The positive pole of the power supply is the current outflow terminal in the meter. After the capacitor is fully discharged, connect the red pen of the multimeter to the positive pole of the electrolytic capacitor, and the black pen to the negative pole of the electrolytic capacitor to measure the positive insulation resistance. On the contrary, the reverse insulation resistance can be measured by connecting the red pen of the multimeter to the negative pole of the electrolytic capacitor and the black pen to the positive pole of the electrolytic capacitor.
