How do you bench test a capacitor?


Quick Answer

To bench test a start or run capacitor in a home appliance or other electrical equipment, use a multimeter to measure the unit's capacitance — how much electrical charge it can store. Check the capacitor's capacitance and voltage rating, and compare to the results obtained from the multimeter to determine how effectively it's functioning.

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Full Answer

As working with electrical equipment can be dangerous, do not attempt to test a capacitor unless you know the proper safety precautions to take. First disconnect the power supply, and remove the capacitor from the appliance. To avoid an electrical shock, discharge the capacitor's remaining charge, either by placing a screwdriver across the terminals to short it or attaching the terminals to a low-wattage light bulb.

Using either an analogue or a digital volt meter, set the meter to 1k ohms, and touch its test leads to the capacitor's terminals twice, switching the leads. If the needle moves or the display shows an open line, the capacitor is still functioning. If there is no movement, the capacitor is dead and must be replaced. To test a live capacitor's effectiveness, use the capacitance setting on a digital multimeter and compare the results to the capacitor's rating. A reading lower than 6 percent indicates it should be replaced.

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