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# How to check a Capasitor using digital multimeter?

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#### kengloong

##### Member level 4
check capasitor

How to check a Capasitor either it is working or fail using digital multimeter?

checking stored charge with multimeter

Not easy. Can charge it from a constant voltage source via a resistor and measure charging time depending on the resistor value.You must choose a resistor that for the given capacitor will give a charging time of a few seconds. Remember the time constant is R*C. Does not work for small capacitors or large resistors because of the input resistance of the multimeter and is only an order of magnitude accurate. Else you can measure the voltage drop in series with a known resistor if you have an AC voltage source. Or you can built your own capacitometer there are many circuits available.

ptmsl wrote....
Can charge it from a constant voltage source via a resistor and measure charging time depending on the resistor value.You must choose a resistor that for the given capacitor will give a charging time of a few seconds. Remember the time constant is R*C. Does

YES..SOUNDS LOGICALLY CORRECT ... but how to measure/identify that ur capacitor has charged so that we can measure time constant as you said

Use your multimeter (its sampling and refresh rates must be relatively fast). As I wrote, this will give you a very rough approximation of the actual value probably an order of magnitude. Dont expect to get the exact value from such a measurement. If your capacitor is 47uF for instance charging it through a 100K resistor should take a few seconds to charge. If it charges instantly then it is probably faulty same stands if it never charges to the value of the DC source. Also this will not show the value of the ESR. Like in most cases debugging electronic circuits and components without at least an osciloscope is very hard.

to check if a capacitor is working properly or not, you can use an ohmmeter. first, short the terminals of the capacitors to discharge the stored charge of the capacitor. then connect the ohmmeter across the capacitor. the ohmmeter should move from 0 ohms to large resistance or open ckt. if it does, it works properly

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