Using a digital multimeter to estimate actual capacitance
When estimating the capacitance of a 0.1 μ F to several thousand microfarads capacitor using a digital multimeter, the resistance range can be selected according to Table 5-1, which provides the range of measurable capacitance and corresponding charging time. The data listed in the table also has reference value for other models of digital multimeters.
The principle for selecting the resistance range is: when the capacitance is small, a high resistance range should be selected, while when the capacitance is large, a low resistance range should be selected. If using high impedance range to estimate large capacity capacitors, due to the slow charging process, the measurement time will last for a long time; If a low resistance level is used to check a small capacity capacitor, due to the extremely short charging time, the instrument will continuously display overflow and the change process cannot be seen.
How to judge the quality of air conditioning capacitors
Check with a digital multimeter, set the multimeter to the appropriate resistance range, and make sure the red and black probes touch the two poles of the tested capacitor. At this point, the displayed value will gradually increase from 000 until the overflow symbol "1" is displayed. If 000 is consistently displayed, it indicates an internal short circuit in the capacitor. If overflow is consistently displayed, it may be due to an open circuit between the internal poles of the capacitor, or it may be due to an inappropriate selection of the resistance level.
In order to view the charging process of capacitors on the display screen, different resistance levels should be selected for capacitors of different capacities. The principle for selecting the resistance range is: when the capacitor is large, the low resistance range should be selected; When the capacity of the capacitor is small, a high resistance range should be selected. If a low resistance level is used to check a small capacity capacitor, due to the short charging time, overflow will continue to be displayed and the change process cannot be seen, making it easy to mistake the capacitor for an open circuit. If using high impedance mode to check large capacity capacitors, due to the slow charging process, the measurement time needs to be relatively long. For capacitors above 0.1~1000uF, the resistance range can be selected according to the table below (the charging time in the table refers to the time required for the display range to change from 000 to overflow).
