Procedures for Measuring Capacitance Using a Digital Multimeter
A pointer multimeter can only check the quality of capacitors (the open circuit disadvantage of small capacity capacitors should not be different) and roughly estimate the size of capacitors. It cannot accurately measure the size of capacitors. Generally, capacitance meters, digital multimeters, and specialized capacitance measuring instruments are required to measure the capacitance of capacitors. When measuring the capacitance of a capacitor with a digital multimeter, it is important to note that not all capacitors can be measured, and it should be determined based on the measurement range of the digital multimeter. Some digital multimeters have multiple capacitance measurement gears, which can measure 2nF~2; The capacitance of tF can be measured from ⒛ nF to ⒛ 0ctF, while some digital multimeters only require one ⒛ 0ptF capacitance measurement gear.
A digital multimeter with a gear for measuring capacitance can be operated according to its gear to measure its capacity. To select a suitable range for measurement, it is assumed that the capacitance of the capacitor is greater than the maximum range of the meter, and measurement cannot be carried out.
A digital multimeter without a capacitance range can only roughly measure the quality of the capacitance, whether there is a short circuit, and whether there is capacity. By using the resistance mode, a DC resistance test and charge discharge test can be conducted on capacitors to determine their capacity and leakage.
When using a digital multimeter to measure the capacitance of a capacitor, place the digital multimeter in the capacitance range, select the appropriate range based on the size of the capacitance, and after the tested capacitor is fully discharged, directly insert the tested capacitor into the test hole or touch the two probes separately for measurement. The flashing screen of the digital multimeter will directly display the capacity of the capacitor to be tested.
Assuming that the flashing value is equal to or very close to the nominal capacity, it indicates that the capacitor is normal; Assuming that the value of the flashing capacitance to be tested is significantly different from the nominal capacity, check whether its nominal capacity is within the testing scheme of the multimeter. If it exceeds the measurement scheme of the multimeter, (copyright reserved) a multimeter with an appropriate range can be replaced for measurement. If the difference is still too large after replacing the multimeter, it indicates that the capacitance to be tested has deteriorated and cannot be used anymore; Assuming that the flashing value of the tested capacitor is much smaller than the nominal capacity, it indicates that the tested capacitor has been damaged.
Attention:
(1) Assuming that the capacitance of the tested capacitor exceeds the measurement scheme of a multimeter, a digital multimeter cannot be used for measurement.
(2) The method of connecting the probes of a digital multimeter is opposite to that of a pointer multimeter. The black probe of a pointer multimeter is connected to the positive terminal of the power supply inside the meter, which is the current outflow end of the meter; The red probe of the digital multimeter is connected to the positive terminal of the power supply inside the meter, which is the current outflow terminal inside the meter. After the capacitor is fully discharged, connect the red probe of the multimeter to the positive pole of the electrolytic capacitor and the black probe to the negative pole of the electrolytic capacitor to measure the positive insulation resistance. On the contrary, connecting the red probe of a multimeter to the negative electrode of an electrolytic capacitor and the black probe to the positive electrode of the electrolytic capacitor can measure the reverse insulation resistance.
