how to measure ESR of capacitor??

[jaysenghani]

i want to measure capacitor using simple multimeter and oscilloscope .

please suggest any idea to measure ESR using DSO .

i have tektronix DSO.

 

[Kripton2035]

all you need to konw is here : **broken link removed**
and more specific at the 5th line.
regards,

 

[pebe]

You could use the bridge method, using a scope as the indicator. The ratio arm on one side of the bridge would be a potentiometer. The top arm of the other side of the bridge would a poly cap (say, 1uF) with almost zero ESR, in series with a variable resistor. The bottom arm would be the cap under test. The bridge would be energized with a 50Hz voltage, as would the scope's X input. The output of the bridge would be fed to the scope's Y input.

When switched on, the scope would show a sloping ellipse. To zero the bridge, first adjust the ratio arm until the ellipse is horizontal, then adjust the variable resistor until the ellipse reduces to a single line. Then measure the resistances of the two sides of the ratio arm, and the variable resistor.

The phase angle of currents in the standard and test caps would then be the same. So knowing the value of the two ratio arms and the standard cap you can calculate the value of the test cap. Then knowing the resistance in series with the standard cap (ie. the variable resistor), you can calculate the ESR of the cap under test.